Transcript Clinical Oral Microbiology

By David R Telles, DDS
Diplomate of the American Board of Oral and
Maxillofacial Surgery
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Bacteria can be distinguished from one another by their
morphology (size, shape, and staining characteristics) via:
◦ Metabolic
◦ Antigenic
◦ genetic characteristics
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Difficult to differentiate by size, but do have different shapes
Examples
◦ Spherical bacterium (e.g. Staphylococcus): coccus
◦ Rod-shaped bacterium (E. coli) : is a bacillus; and the snakelike
treponeme is a spirillum.
◦ Branched filamentous (e.g. Nocardia and Actinomyces): similar to
fungi.
◦ Aggregates
 grapelike clusters of Staphylococcus aureus
 diplococcus observed in Streptococcus or Neisseria species.
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Prok vs. Eukaryotes
Differentiated based on morphology
Gram Negative vs. Gram Positive
Gram staining
Bacterial Classification
Host defenses against bacterial infection
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Bacterial chromosome = dsDNA, circular contained in the
nucleoid
Plasmids - smaller, circular, extrachromosomal DNA
◦ commonly found in GN bact
◦ selective advantage via resistance to one or more antibiotics.
GP vs. GN
bacterial ribosome = 30S + 50S subunits, forming a 70S
ribosome -- unlike the eukaryotic 80S (40S + 60S) ribosome.
Cyto membr: no steroids in all spp. except mycoplasma
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A. GP: thick peptidoglycan
layer
◦ teichoic
◦ lipoteichoic acids.
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B. GN bacterium
◦ thin peptidoglycan layer
◦ outer membrane w/
 LPS
 Phospholipids
 Proteins
◦ peri-plasmic space
 transport, degradative, and cell
wall synthetic proteins
◦ Membranes joined to the
cytoplasmic membrane at
adhesion points and is
attached to the peptidoglycan
by lipoprotein links.
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Thick, multilayered cell wall
Peptidoglycan (150 to 500 Å) surrounding the
cytoplasmic membrane
◦ meshlike exoskeleton similar fxn to exoskeleton
◦ sufficiently porous -- diffusion of metabolites
◦ essential for: structure, replication, and survival
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Upon infection peptidoglycan interferes with:
◦ phagocytosis -- mitogenic (stimulates mitosis of lymphocytes)
◦ pyrogenic
enzymes that catalyze the reaction:
1) D-alanine
2) D-alanine transpeptidase-carboxypeptidases.
 are the targets of β-lactam antibiotics and are
called penicillin-binding proteins.
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Peptidoglycan
◦ Susceptible to lysozyme
 Found in human tears/mucus
 Lysozyme degrades glycan backbone of the peptidoglycan
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W/o peptidoglycan  succumb osmotic pressure differences + lyse
Other Cell Wall Components
◦ Teichoic - water-soluble polymers of polyol phosphates, which are covalently linked to the
peptidoglycan
 Important factors in virulence
◦ Lipoteichoic acids - fatty acid and are anchored in the cytoplasmic membrane
 common surface antigens that distinguish bacterial serotypes and
 promote attachment to other bacteria and…
 specific receptors on mammalian cells (ADHERENCE)
 endotoxic-like
◦ Complex polysaccharides (AKA C polysaccharides).
◦ Proteins e.g. M protein of streptococci + R protein of staphylococci
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Teichoic Acid structure
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More complex than GP CWs
2 layers external to the cytoplasmic membrane
External to the cytoplasmic membrane
◦ thin peptidoglycan layer -- only 5% to 10% of CW by weight
◦ no teichoic or lipoteichoic
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Outer membrane
◦ unique to GN bacteria
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Periplasmic space –
◦ hydrolytic enzymes - important to cell bkdwn of macromolecules for metabolism.
◦ proteases, phosphatases, lipases, nucleases, and carbohydrate-degrading enzymes
◦ lytic virulence factors e.g.:
 as collagenases, hyaluronidases, proteases, and β-lactamase are in the periplasmic space.
◦ sugar transport systems and other binding proteins to facilitate the uptake of different
metabolites and other compounds.
◦ binding proteins -- chemotaxis system  senses external environment of the cell.
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Outer membrane maintains
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Lipopolysaccharide (LPS). -- AKA endotoxin
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interleukin-1, interleukin-6, tumor necrosis factor,
fever + possibly cause shock
follows the release of large amounts of endotoxin into the blood stream.
Porins
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Found on outer leaflet
amphipathic molecule (hydrophobic /hydrophilic ends)
a powerful stimulator of immune responses
activates B cells + induces macrophage and other cells to release
“Shwartzman reaction” (DIC)
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bacterial structure/permeability
barrier to large molecules
protection from adverse environmental conditions
proteins which traverse the lipid bilayer -- transmembrane proteins.
allow the diffusion of hydrophilic molecules <700 Da in mass through the membrane.
********allow passage of metabolites and small hydrophilic antibiotics,
Outer membrane conn. to the cyto. membr at adhesion sites and is tied to the peptidoglycan by
lipoprotein
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lipoprotein -- covalently attached to the peptidoglycan + anchored in the outer membrane
Route for the delivery of newly synthesized outer membrane components to the outer membrane.
The lipopolysaccharide of the gramnegative cell envelope.
A. Segment of the polymer showing the
arrangements of the major
constituents.
B. Stucture of lipid A of Salmonella
typhimurium.
C. Polysaccharide core.
D. Typical repeat unit (S. typhimurium).
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Outer Membr is held together by
◦ divalent cation (Mg+2 and Ca+2) linkages
◦ between P on LPS molecules + hydrophobic
interactions between LPS + proteins.
◦ stiff, strong membrane
◦ disrupted by
 antibiotics (e.g., polymyxin)
 removal of Mg and Ca ions (chelation EDTA).
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Capsule
◦ (in GP or Gngram) loose polysaccharide or protein
layers
◦ If loosely adherent + nonuniform in density =
slime layer.
◦ AKA glycocalyx
◦ Bacillus anthracis
 exception to this rule
 produces a polypeptide capsule
◦ capsule is hard to see in a microscope but can be
visualized by the exclusion of India ink
Porphymonas spp.
Pseudomonas spp.
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Capsule
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Flagella
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poorly antigenic and antiphagocytic
major virulence factor (e.g., Streptococcus pneumoniae)
a barrier to toxic hydrophobic molecules
Promote adherence to other bacteria or to host tissue surfaces
E.g. Streptococcus mutans = dextran and levan capsules -- means by which the bacteria attach to the enamel
ropelike propellers composed of helically coiled protein subunits
anchored in the bacterial membranes through hook and basal body
motility (chemotaxis) toward food and away from poisons.
express antigenic and strain determinants.
Fimbriae (pili) (Latin for “fringe”)
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hairlike structures on the outside of bacteria
protein subunits (pilin)
smaller in diameter (3 to 8 nm versus 15 to 20 nm[flagella]) + not coiled in structure.
Typically peritrichously (uniformly) over the entire surface of the bacterial cell.
promote adherence to other bacteria or to the host
AKA: adhesins, lectins, evasins, and aggressins
important virulence factor for
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E. coli colonization and infection of the urinary
Neisseria gonorrhoeae
F pili (sex pili)
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promote the transfer of large segments of bacterial chromosomes between bacteria.
encoded by a plasmid (F).
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Spores
◦ Some GP but never GN
◦ Bacillus + Clostridium spore formers
◦ harsh environments  bacteria convert from
vegetative state to a dormant state (spore)
◦ Basis of autocalving testing
◦ The bacterial cell-wall proteoglycan can be attacked by lysozyme.
◦ Bacteria release peptides which are chemotactic for polymorphs.
◦ Polymorphs and macrophages use receptors for bacterial sugars to bind and slowly
phagocytose them.
◦ Bacteria induce macrophages to release inflammatory cytokines such as interleukins
1 and 6 and tumour necrosis factor α (TNFα).
◦ Bacterial lipopolysaccharides and endotoxins activate the alternative complement
pathway, generating opsonizing C3b and iC3b on the bacterial surface. The
membrane attack complex (MAC) can lyse Gram-negative but not Gram-positive
bacteria.
◦ Bacterial polysaccharides (e.g. pneumococcal) with multiple repeated epitopes may
activate B cells independently of T helper cells because of their ability to cross-link Bcell receptors (BCRs). The resultant mainly IgM antibodies efficiently agglutinate
bacteria and activate the classical complement pathway.
◦ Exogenous processing of phagocytosed bacteria by macrophages results in
presentation of peptide epitopes in the context of MHC-II to TH1 cells. These induce
macrophage activation for efficient bacterial killing.
◦ Processing of bacterial antigens by B cells induces TH2 responses and high-affinity
antibody production: IgG antibodies neutralize soluble bacterial products such as
toxins; IgA antibodies protect mucosal surfaces from bacterial attachment. Immune
complexes activate the classical complement pathway. Phagocytic uptake of bacteria
coated with C3b/iC3b and antibody is rapid and efficient.
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Gram Staining
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Bacterial Shapes
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A powerful test that -- to distinguish between the Gram Positive
and Gram Negative Bacterium
The Process:
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GP = purple
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◦ heat-fixed or otherwise dried onto a slide  stained with crystal violet
◦ Stain ppted with Gram iodine + excess stain removed via washing with the
acetone-based decolorizer.
◦ Counterstain = safranin added to stain any decolorized cells red.
◦ Takes <10 minutes.
◦ Stain is trapped in thick, cross-linked peptidoglycan layer
GN = thin peptidoglycan ∴ no retention of CV  counterstained
safranin  turns red
Mnemonic “P-Purple-Positive.”
NOTE: Not a dependable test for mycobacteria
◦ Due to waxy outer shell
◦ distinguished w/ acid-fast stain
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Staphylococcus
◦ Gram-positive cocci
◦ arranged in grape-like clusters.
◦ more than 15 different species medical importance:
 S. aureus, S. epidermidis and S. saprophyticus.
◦ Variety of infections:
 abscesses of organs
 Endocarditis
 gastroenteritis (food poisoning)
 toxic shock syndrome
◦ Infrequently isolated from oral cavity
◦ Higher proportions of S. aureus found in the saliva of healthy subjects
>70yrs.
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S. aureus
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Habitat and transmission
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Toxins and enzymes produced
Characteristics
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human skin esp. anterior nares + perineum.
Domesticated animals
Transmission route: hands, fomites
- Disseminated through air and dust and always present in the hospital environment.
Gram-positive cocci in clusters (cluster formation is due to their ability to divide in
many planes)
non-spore forming
non-motile
some are capsulated
Coagulase Positive
Pathogenicity
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various pyogenic infections (eg, endocarditis, septic arthritis, and osteomyelitis)
Food poisoning
TSS
one of the most common causes of hospital-acquired
 Pneumonia
 Septicemia
 surgical-wound infections.
Superficial infections: common agent of boils, carbuncles, pustules, abscesses, conjunctivitis and wound infections;
Rarely causes oral infections;
Angular cheilitis (together with the yeast Candida) at the angles of the mouth
Deep infections; osteomyelitis, endocarditis, septicaemia, pneumonia.
Predisposing factors for infection are minor and major breaks in the skin, foreign bodies such as sutures, low
neutrophil levels, and injecting drug abuse
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S. aureus
◦ Culture and identification
 Grows aerobically as yellow or gold colonies on blood agar
 Catalase-positive
 Staphylococcus aureus coagulates dilute human serum or rabbit plasma (i.e. it is
coagulase-positive), whereas S. epidermidis does not (coagulase-negative).
 Protein A — latex agglutination test - synthesized by almost all strains of
 special affinity to the Fc fragment of immunoglobulin G (IgG).
 latex particles coated with IgG (and fibrinogen) are mixed with emulsified
suspension of S. aureus on a glass slide, visible agglutination of the latex particles
occurs
 no reaction w/ S. epidermidis
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S. aureus
◦ Treatment and Prevention
 vast majority (> 80%) of strains resistant to β-lactam drugs and
other antibiotics.
 Multiresistance common w/ strains isolated from hospitals
 hospital (nosocomial) infection.
 Penicillin resistance due to β-lactamase encoded by plasmids.
 Antibiotics active against S. aureus:
 Flucloxacillin (stable against β-lactamase)
 Erythromycin
 Fusidic acid (useful for skin infections)
 Cephalosporins
 Vancomycin.
 Cleanliness, hand-washing and aseptic management of lesions
reduce the spread of staphylococci.
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S. epidermidis
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GP cocci clusters
Catalase +, Coagulase –
Adhesion polysaccharide promotes adhesion to medical devices
Novobiocin sensitive
Clinical Presentation:
 Infection of indwelling medical devices (IV, Foley, prosthetic valve)
◦ Pathobio:
 Bacteria of normal skin flora  capsule allows adherence to device 
inoculation to internal site  infection
◦ Treatment and Prevention
 Vancomycin (since most strains resistant to PCN/Cephalosporins)
 Removal of device
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S. saporphyticus
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GP cocci clusters
Catalase +, Coagulase –
Adhesion polysaccharide promotes adhesion to medical devices
Novobiocin resistant
Clinical Presentation:
 Urinary tract infection, Cystitis
◦ Pathobio:
 Bacterial entry via sexual activity  infection/inflam. of UT 
spread to bladder resulting in cystitis
◦ Treatment and Prevention
 TMP-SMX
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Streptococci
 Catalase-negative
 spherical or oval cocci in pairs and chains
 0.7–0.9 μm in diameter
◦ Culture - Hemolytic reactions are produced on blood agar
 α-haemolysis: partial haemolysis and green (viridans) discoloration around the colony
 β-hemolysis: wide, clear, translucent zone of complete haemolysis around the colony, e.g.
Streptococcus pyogenes
 no hemolysis (γ-haemolysis), e.g. non-haemolytic streptococci.
◦ Serology
 Currently 20 Lancefield groups are recognized (A–H and K–V) but not all are equally
important as human pathogens. The following are worthy of note:
 Group A includes the important human pathogen Streptococcus pyogenes
 Group B contains one species, S. agalactiae, an inhabitant of the female genital tract; it causes
infection in neonates
 Group C mainly causes diseases in animals
 Group D includes the enterococci (S. faecalis, etc.) and ranks next to group A in causing
human disease.
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Streptococcus pyogenes (group A)
◦ Habitat and transmission
 human upper respiratory tract and skin; it
 may survive in dust for some time
 Transmission: airborne droplets + contact.
◦ Characteristics
 commensal in the nasopharynx more commonly (about 10%) in children
 β- haemolytic
 Some strains produce mucoid colonies as a result of having a hyaluronic
acid capsule -- contribute to virulence -- resistance to phagocytosis.
◦ Exotoxins and enzymes
 Streptokinase: a proteolytic enzyme which lyses fibrin
 Hyaluronidase: attacks the material that binds the connective tissue, thereby causing
increasing permeability (hence called the ‘spreading factor')
 DNAases (streptodornases): destroy cellular DNA
 Hemolysins (streptolysins, leucocidins): phage-mediated and are responsible for the
characteristic erythematous rash in scarlet fever.
β-haemolytic colonies (e.g. Streptococcus pyogenes) produce complete
translucence of blood agar, whereas α-haemolytic colonies (e.g.
Streptococcus pneumoniae) do not.
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Streptococcus pyogenes (Group A)
◦ Pathogenicity
 tonsillitis and pharyngitis
 peritonsillar abscess (now rare)
 scarlet fever
 mastoiditis and sinusitis
 otitis media (middle-ear infection)
 wound infections leading to cellulitis and lymphangitis
 impetigo (a skin infection).
◦ Complications. *****After an episode of infection some patients develop
complications
-- rheumatic fever/glomerulonephritis/erythema nodosum
- -longlasting effects
 Cellulitis - hyaluronidase mediates subcutaneous spread of infection
 erythrogenic toxin causes the rash of scarlet fever
 post-streptococcal infection, manifesting as rheumatic fever, is caused by
immunological cross-reaction between bacterial antigen + :
 human heart tissue
 acute glomerulonephritis  immune complexes bound to glomeruli
◦ Tx of Choice:
 Penicillin
 All: Erythromycin
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Streptococcus agalactiae (Group B)
◦ Habitat and transmission
 Found in the human vagina; sometimes anorectal carriage occurs.
 Babies acquire infection from mother during delivery/nursing.
◦ Characteristics
 Gram-positive cocci in chains.
◦ Culture and identification
 β-haemolytic
◦ Pathogenicity
 No toxins or virulence factors have been identified. This species causes neonatal
 meningitis and septicaemia
 Associated with septic abortion and gynaecological sepsis.
◦ Treatment and prevention
 Penicillin is the drug of choice
 ALL: erythromycin
 Prophylactic antibiotics may be given to neonates if the mother is culture-positive.
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Oral Streptococci (“Viridans Streptococci”)
◦ Found mainly in oropharynx
◦ mixed group of organisms
◦ typically α-haemolytic
 some strains are non-haemolytic /β-haemolytic
◦ Four main ‘species groups’:
 salivarius group
 anginosus group
 mitis group.
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Strep
 Recognized species of oral streptococci
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Oral Streptococci
◦ Habitat and transmission
 Large portion of resident oral flora
 ¼ of the total cultivable flora from supragingival/gingival plaque and half of the isolates from
the tongue and saliva are streptococci.
 vertically transmitted
 Infective endocarditis (loosely “viridans streptococci”) is generally a result of their entry into
the bloodstream.
◦ Culture and identification
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Gram-positive cocci in chains
α-haemolytic
Catalase negative
Not inhibited by bile or optochin
◦ Pathogenicity
 major agents of dental caries
 ability to produce sticky, extracellular polysaccharides in the presence of dietary
carbohydrates
 binding of the organisms to enamel and to each other
 important agents of infective endocarditis and some 60% of cases
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Streptococcus pneumoniae (pneumococcus)
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Habitat and transmission
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Characteristics
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α-haemolytic colonies - appear typically as ‘draughtsmen’ due to central indentation
sensitivity to optochin and solubility in bile
The latex agglutination test for capsular antigen in spinal fluid can be diagnostic.
Pathogenicity
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Gram-positive ‘lancet-shaped’ cocci in pairs (diplococci) or short chains
often capsulate
α-haemolytic on blood agar
catalase-negative
facultative anaerobe
Culture and identification
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normal commensal in human URT
4% of the population carry this bacteria in small numbers
Transmission : respiratory droplets.
pneumonia
meningitis
otitis media and sinusitis in children
induces an inflammatory response
polysaccharide capsule retards phagocytosis
Vaccination with antipolysaccharide vaccine helps provide type-specific immunity
Other common diseases caused: lobar pneumonia, acute exacerbation of chronic bronchitis, otitis media, sinusitis, conjunctivitis, meningitis
and, in splenectomized patients, septicaemia.
Treatment and prevention
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Penicillin or erythromycin
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S. pneumoneae
◦ Virulence factors
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Peptostreptococcus
◦ Gram-positive anaerobic cocci
◦ often be isolated from
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dental plaque
female genital tract
carious dentin
subgingival plaque
dentoalveolar abscesses
advanced periodontal disease
◦ Found in “mixed anaerobic infections”-◦ Pathogenic role unclear. Spp.
 P. anaerobius
 P. magnus
 P. micros
◦ For example, peptostreptococci and viridans streptococci [oral flora] -- found in
brain abscesses following dental surgery
 Peptostreptococcus magnus + Peptostreptococcus anaerobius frequently isolated.
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Corynebacterium
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Gram-positive bacilli, non-spore forming rod
Pleomorphism (i.e. coccobacillary appearance)
non-sporing / non-capsulate/non-motile.
In common w/ Mycobacterium+Nocardia spp -- a CW
containing mycolic acid
◦ Imp human pathogens + commensals
◦ Fatal upper respiratory tract infection of childhood -diphtheria
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Corynebacterium diphtheriae
◦ Habitat and transmission
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Human throat and nose, occasionally skin
carry toxigenic organisms up to 3 months after infection
Transmission: respiratory droplets.
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Pleomorphic, non-fastidious, facultative anaerobe
Gram-positive
Club-shaped (tapered at one end) bacilli
2–5 μm in length, arranged in palisades
Divide by ‘snapping fission’
Rods have a beaded appearance
Granules stain metachromatically with special stains such as Neisser methylene blue stain (i.e. the cells are
stained with blue and the granules in red).
◦ Characteristics
◦ Culture and identification
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Grows well at 37°C
Blood tellurite agar  produce distinctive grey-black colonies after 48 hours' incubation at 35°C.
Preliminary identification is helped by the shape and size of the colonies on tellurite agar
Identification via biochemical reactions + demonstration of toxin production.
Toxin production
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Some are non-toxigenic (and hence non-virulent) + normal skin or throat commensals
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Corynebacterium diphtheriae
◦ Toxin production
 exotoxin
 responsible for virulence
 Diphtheria toxin -- exotoxin produced by strains carrying bacteriophages
with the tox gene —
 inhibits protein biosynthesis in eukaryotic cells
 two components:
 subunit A -- ADP ribosylating activity
 subunit B -- binds the toxin to cell surface receptors
 toxin blocks protein synthesis of host cells by inactivating an elongation
factor.
 Macroscopically Rxn is to respiratory mucosa
 production of a grey, adherent pseudomembrane comprising bacteria, fibrin and epithelial
and phagocytic cells
 obstruct the airway + patient may die of asphyxiation.
 If into bloodstream
 affects motor nerves of the myocardium + nervous system
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Corynebacterium diphtheriae
◦ Pathogenicity
 Affects the mucosa of the upper respiratory tract, sometimes skin
 Skin infections usually mixed infections w/ Staphylococcus aureus
and/or Streptococcus pyogenes
◦ Treatment and prevention
 Acute phase
 maintain the airway is critical
 Antitoxin given to neutralize the toxin + penicillin to kill the organisms
 Antibiotics little effect once toxin has spread.
 Immunization highly effective in preventing diphtheria.
 Schick test -- used to demonstrate immunity. Here, the circulating
level of antibody after immunization (or clinical/subclinical infection)
is assessed by inoculating a standardized dose of the toxin.
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Lactobacillus
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GP, non-spore forming, aerobe, rod
saprophytes in vegetable and animal material (e.g. milk)
Some spp. common animal/human commensals inhabiting oral cavity and other parts of the body
Acidophilic - associated with the carious process.
Two main groups:
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Homofermenters -- produce mainly lactic acid (65%) from glucose fermentation (e.g. Lactobacillus casei)
Heterofermenters -- produce lactic acid as well as acetate, ethanol and carbon dioxide (e.g. L. fermentum).
Lactobacillus casei and L. rhamnosus, L. acidophilus and the newly described species
L. oris - common in the oral cavity
Habitat and transmission
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Lactobacilli are found in the oral cavity, gastrointestinal tract and female genital tract. In the oral cavity they constitute less than 1% of the
total flora. Transmission routes are unknown.
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Characteristics
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Culture and identification
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Ferment carbohydrates to form acids (i.e. they are acidogenic) + survive well in acidic milieu (aciduric)
Grow under microaerophilic conditions in the presence of carbon dioxide and at acidic pH (6.0)
Media enriched with glucose or blood promote growth
Selective medium, tomato juice agar (pH 5.0), promotes the growth of lactobacilli while suppressing other bacteria. Identification is by
biochemical reactions.
Pathogenicity
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isolated from deep carious lesions where pH = acidic
lactobacillus count - indication of an individual's caries activity. Although this test is not very reliable, it is useful for monitoring the dietary
profile of a patient because the level of lactobacilli correlates well with the intake of dietary carbohydrate.
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Nocardia
◦ Physiology and Structure
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Gram-positive, non-spore forming rod, Aerobe, Filamentous
Partially acid-fast, filamentous bacilli
Cell wall with mycolic acid.
Strict aerobe capable of growth on most nonselective bacterial
media; however, prolonged incubation (7 days or more) required for
recovery of most isolates.
◦ Virulence
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Specific factors not well-characterized.
Opportunistic pathogen.
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Bronchopulmonary disease.
Primary or secondary cutaneous infections (e.g., mycetoma,
lymphocutaneous infection, cellulitis, subcutaneous abscesses).
Secondary CNS infections (e.g., brain abscesses).
◦ Diseases
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◦ Diagnosis
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Microscopy is sensitive and relatively specific when branching,
partially acid-fast organisms are seen.
Culture is slow, requiring incubation for up to 1 week. Selective
media (e.g., BCYE agar) may be required for isolating Nocardia in
mixed cultures.
◦ Treatment, Prevention, and Control
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Infections are treated with antibiotic therapy with sulfonamides or
antibiotics with proven in vivo activity, and proper wound care.
Exposure cannot be avoided because nocardia are ubiquitous.
Mycetoma caused by
Nocardia brasiliensis.
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Actinomycetes
Diseases of Selected Pathogenic Actinomycetes
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Anctinomyces
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◦
◦
GP, non-spore forming rod, facultative anaerobe, filamentous
not acid-fast
produce chronic, slowly developing infections
form delicate filamentous forms or hyphae
Inhibited by penicillin
Spp:
 Actinomyces israelii
 Actinomyces meyeri
 Actinomyces naeslundii
 Actinomyces odontolyticus
 Actinomyces viscosus
 …responsible for most human infections

Anctinomyces
◦ Pathogenesis and Immunity
 Colonize:
 upper respiratory tract
 gastrointestinal tract
 female genital tract
 ***not normally present on the skin surface
 Cause disease only when the normal mucosal
barriers are disrupted by: trauma, surgery, or
infection.
 “Actinomycosis”
 development of chronic granulomatous lesions 
suppurative and form abscesses connected by sinus
tracts
 Macroscopically: colonies of sulfur granules because
they appear yellow or orange -- masses of filamentous
organisms bound together by calcium phosphate
 Regions of suppuration are surrounded by fibrosing
granulation tissue, which gives the surface overlying the
involved tissues a hard or woody consistency.

Anctinomyces
◦ Treatment and Prevention
 combination of surgical debridement of the
involved tissues + prolonged administration
of antibiotics
 Uniformly susceptible to penicillin
 as well as to erythromycin and clindamycin
 Most spp resistant to metronidazole and the
tetracyclines
 Good oral hygiene + antibiotic prophylaxis
when mouth or GI tract is penetrated can
lower the risk of these infections.
Diseases associated with Peptostreptococcus,
Actinomyces, Propionibacterium, and
Mobiluncus, which are all anaerobic, non-sporeforming, gram-positive bacilli.

Bacillus
◦ GP, Spore forming rod, aerobe
◦ Soil saprophytes
◦ Bacillus anthracis
 Anthrax
◦ B. cereus

Bacillus anthracis

Physiology and Structure





Virulence




The capsule is present in virulent stains.
Virulent strains also produce three exotoxins that combine to form edema toxin (combination of protective antigen and edema factor) and lethal toxin (protective antigen
with lethal factor).
Spores can survive in soil for years.
Epidemiology





Spore-forming gram-positive bacilli.
Facultative anaerobe.
Nonfastidious growth of nonhemolytic colonies that are firmly adherent to the agar surface.
Polypeptide capsule consisting of poly-D-glutamic acid observed in clinical specimens.
B. anthracis primarily infects herbivores with humans as accidental hosts.
Rarely isolated in developed countries but is prevalent in impoverished areas where vaccination of animals is not practiced.
Individuals at risk include people in endemic areas in contact with infected animals or contaminated soil, people who work with animal materials imported from endemic
areas, and military and nonmilitary people exposed to infectious aerosols.
There is significant concern that the spores will be used in bioterrorism.
Diseases



Cutaneous anthrax is the most common form.
Inhalation anthrax is the most deadly form.
Gastrointestinal anthrax is a rare but commonly fatal disease.

Diagnosis

Treatment, Prevention, and Control




Isolation of the organism from clinical specimens (e.g., papule or ulcer, blood).
Ciprofloxacin is the drug of choice; penicillin, doxycycline, erythromycin, or chloramphenicol can be used if susceptible), but the bacteria are resistant to sulfonamides
and extended-spectrum cephalosporins.
Vaccination of animal herds and people in endemic areas can control disease, but spores are difficult to eliminate from contaminated soils.
Animal vaccination is effective, but human vaccines have limited usefulness.

Bacillus cereus
◦
Physiology and Structure



◦
◦
Virulence




◦
Ubiquitous in soils throughout the world.
People at risk include those who consume food contaminated with the bacterium (e.g., rice, meat, vegetables, sauces), those with penetrating
injuries (e.g., to eye), and those who receive intravenous injections.
Diseases

◦
Heat-stable enterotoxin.
Heat-labile enterotoxin.
Spores can survive in soil.
Tissue destruction is mediated by cytotoxic enzymes, including cereolysin and phospholipase C.
Epidemiology


◦
Spore-forming gram-positive bacilli.
Facultative anaerobe.
Nonfastidious growth requirements.
Infections include emetic (vomiting) and diarrheal forms of gastroenteritis; ocular infection following trauma to eye; and other opportunistic
infections.
Diagnosis

Isolation of the organism in implicated food product or nonfecal specimens (e.g., eye, wound).
Treatment, Prevention, and Control



Gastrointestinal infections are treated symptomatically.
Ocular infectious or other invasive diseases require removal of foreign bodies and treatment with vancomycin, clindamycin, ciprofloxacin,
or gentamicin.
Gastrointestinal disease is prevented by proper preparation of food (e.g., foods should be consumed immediately after preparation or
refrigerated).

Clostridium
◦ anaerobic, spore-forming, gram-positive
rods
◦ Four medically important species:




Clostridium
Clostridium
Clostridium
Clostridium
tetani
botulinum
perfringens
difficile.

Propionibacteria
◦
◦
◦
◦
◦
◦
small gram-positive bacilli that
short chains or clumps
found on: skin, conjunctiva, external ear, oropharynx, female genital tract
Anaerobic or aerotolerant, nonmotile, catalase-positive,
ferment carbohydrates  propionic acid major byproduct
Common spp.
 Propionibacterium acnes and Propionibacterium propionicus.
◦ P. acnes
 acne (as the name implies) in teenagers and young adults
 opportunistic infections in patients with prosthetic devices (e.g., artificial heart
valves or joints) or intravascular lines (e.g., catheters, cerebrospinal fluid shunts)
 Contamination with bacteria on the skin at the phlebotomy site.
 Tx: Topical application of benzoyl peroxide and antibiotics. Antibiotics such as
erythromycin and clindamycin have proved effective.

Cocci

Bacilli

Spirochetes
◦ Aerobes: Neisserie
◦ Anaerobes: Veillonelle
◦ Aerobes: Pseudomonas
◦ Aerobes/ or facultative
 Parvobacteria
 Enterobacteria
 Vibrios
 Legionella
 Pasteurellaceae -- Actinobacillus
◦ Anaerobes
 Bacteroides
 Prevotella
 Porphymonas
 Fusobacterium
◦ Aerobes: Leptospira
◦ Anaerobes: Treponema

Cocci
◦ Aerobes: Neisserie
 Neisseria gonorrhoeae and Neisseria meningitidis -strictly human pathogens
 Remaining species commonly present on mucosal
surfaces of the oropharynx and nasopharynx
 Aerobic, gram-negative cocci typically arranged in
pairs (diplococci)
 “coffee bean” appearance
 Non-motile, no endospores
 oxidase-positive
 Most produce catalase

Neisseria gonorrhoeae
 Physiology and Structure
 Gram-negative diplococci with fastidious growth requirements..
 Oxidase- and catalase-positive; acid produced from glucose oxidatively.
 Diseases
 See table on last slide
 Diagnosis
 Gram stain of urethral specimens is accurate for symptomatic males only.
 Culture is sensitive and specific but has been replaced with molecular probe techniques in many
laboratories.
 Treatment, Prevention, and Control
 Ceftriaxone, cefixime, ciprofloxacin, or ofloxacin can be administered in uncomplicated cases.
 In vitro susceptibility should be determined in cases unresponsive to therapy, because antibiotic
resistance is increasing.
 Penicillin should be avoided, because resistance is common.
 Doxycycline or azithromycin should be added for infections complicated by Chlamydia.
 For neonates, prophylaxis with 1% silver nitrate; ophthalmia neonatorum is treated with
ceftriaxone.
 Prevention consists of patient education
 Effective vaccines are not available.

Neisseria meningitidis
◦
Physiology and Structure




◦
Gram-negative diplococci with fastidious growth requirements.
Grows best at 35°C to 37°C in a humid atmosphere.
Oxidase- and catalase-positive; acid produced from glucose and maltose oxidatively.
Outer surface antigens include polysaccharide capsule, pili, and lipooligosaccharides (LOS)
Virulence




Capsule protects bacteria from antibody-mediated phagocytosis.
Specific receptors for meningococcal pili allow colonization of nasopharynx.
Bacteria can survive intracellular killing in the absence of humoral immunity.
Endotoxin mediates most clinical manifestations.
◦
Transmission
◦
Diseases


◦
See table on neisseria slide
Diagnosis



◦
Person-to-person spread occurs via aerosolization of respiratory tract secretions.
Gram stain of cerebrospinal fluid is sensitive and specific but is of limited value for blood specimens (too few organisms are generally
present except in overwhelming sepsis).
Culture is definitive, but organism is fastidious and dies rapidly when exposed to cold or dry conditions.
Tests to detect meningococcal antigens insensitive and nonspecific.
Treatment, Prevention, and Control





Breast-feeding infants have passive immunity (first 6 months).
Treatment is with penicillin (drug of choice), chloramphenicol, ceftriaxone, and cefotaxime.
Chemoprophylaxis for contacts is with rifampin or sulfadiazine (if isolated organism is susceptible).
For immunoprophylaxis, vaccination is an adjunct to chemoprophylaxis; it is used only for serogroups A, C, Y, and W135; no effective
vaccine is available for sero-group B.
Polysaccharide vaccines conjugated with protein carriers offer protection for infants younger than 2 years

Cocci
◦ Anaerobes: Veillonelle
 obligate anaerobic
 Gram-negative cocci
 Freq. isolated from oral samples. Three oral species are
recognized:
 Veillonella parvula
 V. dispar
 V. atypica.
 Veillonella parvula





Gram-negative, small anaerobic cocci
Found in human oral cavity -- in dental plaque
‘benevolent organisms’ in relation to dental caries
metabolize the lactic acid  reduce ability to solubilize enamel
No known pathogenic potential.

Bacilli
◦ Aerobes: Pseudomonas
 GN, aerobe, rods

Peudomonas aerugenosa
◦
◦
Physiology and Structure





Small gram-negative bacilli.
Strict aerobe.
Non-fermenter.
Simple nutritional requirements.
Mucoid exopolysaccharide capsule.

Ubiquitous in moist environmental sites in the hospital (e.g., flowers, sinks, toilets, respiratory and dialysis
equipment) as well as in nature.
No seasonal incidence of disease.
Can transiently colonize the respiratory and gastrointestinal tracts of hospitalized patients, particularly those
treated with broad-spectrum antibiotics, exposed to respiratory therapy equipment, or hospitalized for extended
periods.
Epidemiology


◦
◦
◦
Diseases





Pulmonary infections (common in patients with cystic fibrosis).
Burn wound infections and other skin and soft tissue infections (can be life-threatening).
Urinary tract infections (primarily in catheterized patients).
External otitis (varying from mild “swimmer's ear” to malignant otitis externa).
Eye infections (commonly associated with contaminated contact lens cleaning fluids).

Readily grow on common laboratory media. P. aeruginosa is identified by colonial characteristics (e.g., hemolytic,
green pigment, grapelike odor) and simple biochemical tests (e.g., positive oxidase reaction).
Diagnosis
Treatment, Prevention, and Control




Combined use of effective antibiotics (e.g., aminoglycoside and β-lactam antibiotics) frequently required. Mono
therapy is generally ineffective and can select for resistant strains.
Hyperimmune globulin and granulocyte transfusions may be beneficial in selected infections in
immunocompromised patients.
Hospital infection control efforts should concentrate on preventing contamination of sterile medical equipment and
nosocomial infections.
Unnecessary use of broad-spectrum antibiotics can select for resistant organisms such as P. aeruginosa

Virulence factors assocaited w/ Pseudomonas aeruginosa

Bacilli
◦ Aerobes/ or facultative
 Parvobacteria





Haemophilus
Brucella
Bordetella
Pasteurella
Eikenella

Haemophilus
◦
◦
Physiology and Structure




Virulence


◦
◦
◦
H. influenzae type b is clinically most virulent (with PRP, [polyribitol phosphate] in capsule).
Haemophilus adhere to host cells via pili and nonpilus structures.
Patients at greatest risk for disease are those with inadequate levels of protective antibodies, those with depleted complement, and
those who have undergone splenectomy.
Diseases

◦
Small, pleomorphic, gram-negative bacilli or coccobacilli.
Facultative anaerobes, fermentative.
Most species require X and/or V factor for growth.
H. influenzae subdivided serologically (types a to f), biochemically (biotypes I to VIII), and clinically (biogroup aegypticus).

H. influenzae is responsible for meningitis, epiglottitis, cellulitis, arthritis, otitis, sinusitis, lower respiratory tract disease, conjunctivitis, and
Brazilian purpuric fever.
H. ducreyi is responsible of the ulcerative genital infection chancroid.
Diagnosis



Microscopy is a sensitive test for detecting H. influenzae in CSF, synovial fluid, and lower respiratory specimens.
Culture is performed using chocolate agar.
Antigen tests for H. influenzae type b are less useful following the introduction of vaccination for this organism.
Treatment, Prevention, and Control



Haemophilus infections are treated with broad-spectrum cephalosporins, azithromycin, or fluoroquinolones; many strains are resistant to
ampicillin.
Active immunization with conjugated PRP vaccines prevents most H. influenzae type b infections.
Rifampin prophylaxis is used to eliminate carriage of H. influenzae in children at high risk for disease.

Bacilli
◦ Aerobes/ or facultative
 Parvobacteria
 Eikenella






commensals of the human oral cavity + intestine
linked to periodontal diseases
Eikenella corrodens
capnophilic, Gram-negative, short coccobacillary
On non-selective media -- corrode the agar surface
Human infection results from predisposing factors
 trauma to a mucosal surface
 may cause extraoral infections
 brain /abdominal abscesses
 Peritonitis
 Endocarditis
 osteomyelitis
 Meningitis
 Also associated with human bites or fist-fight injuries.

Bacilli
◦ Aerobes/ or facultative
 Enterobacteria




Yersinia
Salmonella
Escherichia coli
Shigella

Escherichia coli
◦
Physiology and Structure



◦
◦
◦
Gram-negative bacilli, Facultative anaerobe, fermenter, oxidase negative.
Outer membrane makes the organisms susceptible to drying.
Lipopolysaccharide consists of outer somatic O polysaccharide, core polysaccharide (common antigen), and lipid A
(endotoxin).
Virulence





Endotoxin.
Permeability barrier of outer membrane.
Adhesins (e.g., colonization factor antigen, Dr adhesins).
Exotoxins (e.g., heat-stabile and heat-labile enterotoxins, Shiga toxins).
Invasive capacity.




Bacteremia (most commonly isolated gram-negative bacillus).
Urinary tract infection (most common cause of bacterial UTIs; limited to bladder (cystitis) or can spread to kidneys
(pyelonephritis) or prostate (prostatitis).
At least six different pathogenic groups cause gastroenteritis (ETEC, EPEC, EIEC, EHEC, EAEC, DAEC);
most cause diseases in developing countries, although EHEC is an important cause of hemorrhagic colitis (HC) and
hemolytic uremic syndrome (HUS) in the United States.
Neonatal meningitis (usually with strains carrying the K1 capsular antigen).
Intra-abdominal infections (associated with intestinal perforation).

Organisms grow rapidly on most culture media.

Infections are controlled by use of appropriate infection-control practices to reduce the risk of nosocomial
infections (e.g., restricting use of antibiotics, avoiding unnecessary use of urinary tract catheters).
Maintenance of high hygienic standards to reduce the risk of exposure to gastroenteritis strains.
Proper cooking of beef products to reduce risk of EHEC infections.
Most common aerobic, gram-negative bacilli in the gastro-intestinal tract.
Diseases


◦
Diagnosis
◦
Treatment, Prevention, and Control



Bacilli
◦ Aerobes/ or facultative
 Vibrios
 curved bacilli,
 most prominent:
 Vibrio cholerae
 Vibrio parahaemolyticus
 Vibrio vulnificus

Vibrio cholerae Infections
◦
◦
Physiology and Structure





Virulence


◦
◦
◦
◦
◦
Cholera toxin is primarily responsible for the watery diarrhea characteristic of this species.
Adherence factors are important for establishing the initial colonization in the intestines, permitting the toxin to function.
Organism found in estuarine and marine environments worldwide (including along the coast of the United States) associated with
chitinous shellfish.
Direct person-to-person spread is rare because the infectious dose is high.
The infectious dose is high because most organisms are killed by stomach acids.
Disease




Cholera.
Presentation can range from mild disease to severe life-threatening disease.
Disease is characterized by profuse watery diarrhea.
Death is caused by electrolyte abnormalities and massive fluid loss.
Diagnosis

◦
Curved gram-negative bacilli.
Facultative anaerobe.
Fermenter.
Strains subdivided by their O cell wall antigens.
Two biotypes of V. cholerae O1 strains—E1 tor and classical (this is important for epidemiologic classification of isolates).
Culture should be performed early in course of disease with fresh stool specimens.
Treatment, Prevention, and Control





Fluid and electrolyte replacement are crucial.
Antibiotic therapy reduces the bacterial burden and exotoxin production, as well as duration of diarrhea.
Doxycycline (adults), trimethoprim-sulfamethoxazole (children), or furazolidone (pregnant women) is administered.
Improved hygiene is critical for control.
The killed parenteral vaccine is of no value, but the newer oral vaccine has some protective value.

Bacilli

---------------

◦ Aerobes/ or facultative
Pasteurellaceae -- Actinobacillus
◦ small, facultatively anaerobic, gram-negative bacilli
◦ grows slowly
◦ Actinobacillus actinomycetemcomitans
 most important human pathogen
 Actinomyces.
◦ colonize the oropharynx of humans/animals
◦ responsible for periodontitis, endocarditis, bite wound infections,
opportunistic infections.
◦ Spreads from the oropharynx through the blood stream + adheres to the
damaged heart valve
◦ Treatment
 Serious infections with Actinobacillus species are treated with ampicillin,
either alone or in combination with an aminoglycoside.
 Resistant Strains to ampicillin  treated with cephalosporins or
fluoroquinolones.

Bacilli
◦ Anaerobes
 Bacteroides
 obligately anaerobic, short
Gram-negative rods or
coccobacilli.
 Bacteroides spp. restricted to
species found in the gut
(taxonomic change)
 most common agents of serious
anaerobic infections
 B. fragilis is the main pathogen.

Bacilli
◦ Anaerobes
------------------
◦ Bacteroides fragilis
 Habitat and transmission
 Bacteroides species are the most predominant flora in the intestine
 serious anaerobic infections such as intra-abdominal sepsis, peritonitis, liver
and brain abscesses, and wound infection.cs
 Strictly anaerobic, Gram-negative, non-motile, non-sporing bacilli, but may
appear pleomorphic.
 polysaccharide capsule=important virulence factor.
 Culture and identification
 slow growth on blood agar -- grey to opaque, translucent colonies
 grow well in Robertson's cooked meat medium supplemented with yeast
extract.
 Pathogenicity
 Mainly the result of its endotoxin and proteases
 No exotoxin
 Many Bacteroides infections are polymicrobial in nature.
 Treatment and prevention
 Sensitive to metronidazole and clindamycin.
 Penicillin resistance is due to β-lactamase production.
 Bacteroides spp. are normal gut commensals

Bacilli
◦


Anaerobes
----------Fusobacterium
◦
Fusobacterium nucleatum
 Habitat and transmission




Characteristics


Gram-negative, strictly anaerobic, cigar-shaped bacilli with pointed ends
Culture and identification



F. nucleatum subsp. polymorphum (healthy gingival crevice), F. nucleatum subsp. nucleatum (periodontal pockets)
F. nucleatum subsp. Vincenti
Infections usually endogenous.
blood agar -- dull, granular colonies with an irregular, rhizoid edge
odoriferous hydrogen sulphide and methylmercaptan  halitosis.
Pathogenicity



endotoxin
Fusobacterium nucleatum is usually isolated from polymicrobial infections
Combination with oral spirochaetes (Treponema vincentii and others) it causes the classic fusospirochaetal infections:





ANUG
Vincent's angina -- an ulcerative tonsillitis causing tissue necrosis often due to extension of acute ulcerative gingivitis.
Cancrum oris or noma: a sequel of acute ulcerative gingivitis with resultant gross tissue loss of the facial region.
Important bridging organisms between early + late colonizers during plaque formation.
Antibiotic sensitivity and prevention


Fusobacteria are uniformly sensitive to Penicillin
Sensitive to metronidazole

Bacilli
◦ Anaerobes
 Prevotella





Prevotella spp. include saccharolytic oral and genitourinary species; some species are periodontopathic.
Porphyromonas and Prevotella species are referred to as black-pigmented anaerobes
- form a characteristic brown or black pigment on blood agar
i.e. # of pigmented/nonpigmented species
- moderately saccharolytic
all produce acetic and succinic acid from glucose
Prevotella spp.
 Habitat and transmission
 human oral cavity
 P.intermedia associated more with periodontal disease
 P. nigrescens is isolated more often from healthy gingival sites.
 Culture and identification

Non-motile, Gram-negative rods; brown-black colonies on blood agar (when
pigmented).
 Pathogenicity
 Prevotella intermedia is a true periodontopathogen.
 Oral non-pigmented species such as P. buccae, P. oralis and P. dentalis are
isolated on occasion from healthy subgingival plaque

Bacilli
◦ Anaerobes
◦ ------------
Porphyromonas gingivalis
 Habitat and transmission
 Found almost solely at subgingival sites -- advanced periodontal disease.
 Sometimes recovered from tongue/tonsils.
 Characteristics
 Non-motile, short, pleomorphic, Gram-negative rods.
 Culture and identification
 Grows anaerobically, with dark pigmentation w/media containing lysed
blood
 Pathogenicity




An aggressive periodontal pathogen in both humans and animals
Fimbriae mediate adhesion
capsule defends against phagocytosis
Virulence Factors
 proteases that destroy immunoglobulins, complement and haemsequestering proteins, a haemolysin and a collagenase

Capnocytophagia
◦ filamentous gram-negative bacilli capable of aerobic and anaerobic growth in the
presence of carbon dioxide
◦ created for fusiform species isolated from periodontal pockets which grow under
capnophilic conditions
◦ ability to glide over routine blood agar
◦ Spp. i.e.:Capnocytophaga ochracea (type species), C. sputigena, C. gingivalis, C.
granulosa and C. haemolytica.
◦ Habitat
 The primary ecological niche is the subgingival area.
◦ Characteristics
 Long, thin fusiform organisms that demonstrate gliding motility seen on brightfield microscopy.
◦ Culture and identification
 Facultative anaerobes
 strains require CO2 for growth
◦ Pathogenicity
 Opportunist pathogens -- immunocompromised patients
 some strains produce an IgA1 protease.
◦ Gram + Rods
 Corynebacterium
 Rothia
 Diphtheroids
◦ Gram – Rods
 Eikenella corrodens
 Haemophilus
 Enterobacteriaceae



Klebsiella
Pseudomonas
Escherichia
◦ Gram + Cocci

Streptococcus

Alpha-hemolytic
 Strep. Salivarius
 Strep. Mitior
 Strep. sanguis
 Strep. Mutans
 Strep. milleri
Aerobes
◦ Gram + rods






Actinomyces
Lactobacillus
Propionibacterium acnes
Bifidobacterium
Eubacterium
Clostridia
◦ Gram – rods
 Bacteroides

B. fragalis


P. gingivalis
P. endontalis




P. intermedius
P. melaninogenicus
P. loescheii
P. oralis
 Prophymonas
 Prevotella
Anaerobes

Gram + cocci
◦ Streptococcus

 Fusobacterium
 Beta-hemolytic
 F. nucleatum
 Strep. pyogenes
 Wolinella
 Capnocytophagia
 Enterococci
◦ Staphylococcus
 S. aureus
 S. epidermidis



Spriochetes
◦ Treptonema
Aerobes
Gram + cocci
◦ Peptostreptococcus
◦ Streptococcus
Gram – cocci
◦ Neisseria
◦ Branhamella
Gram – rods

Gram - cocci
◦ Veillonella
Anaerobes

Important to differentiate between Aerobes
and Anaerobes since give status of disease
progression i.e.:
◦ Periodontal Dz
◦ Type of infection: acute vs. chronic
 Cellulitis vs. abscess
◦ Antibiotic coverage
◦ Severity of infection: mixed vs. isolate predominate
microbe

Genus Streptococcus
◦ Gram+ cocci in chains
- facultative anaerobes
- variable haemolysis but α-haemolysis most
common
◦ 1) mutans group
 Main species: Streptococcus mutans serotypes c, e, f;
S. sobrinus serotypes d, g; S. cricetus serotype a; S.
rattus serotype b; S. ferus; S. macacae; S. downei
serotype h.
 Main intraoral sites and infections: tooth surface,
dental caries.

Genus Streptococcus

2) salivarius group
◦ Main species: Streptococcus salivarius; S.
vestibularis.
◦ Main intraoral sites and infections: dorsum of
tongue and saliva
-S. vestibularis mainly reside in the vestibular
mucosa (hence the name); not a major oral
pathogen.

Genus Streptococcus
◦ 3) anginosus group
 Main species: Streptococcus constellatus; S.
intermedius; S. anginosus.
 Cultural characteristics: CO2-dependent; form small,
non-adherent colonies on MSA.
 Main intraoral sites and infections: gingival crevice;
dentoalveolar and endodontic infections

Genus Streptococcus

4) mitis group
◦ Main species: Streptococcus mitis; S. sanguis; S.
gordonii; S. oralis; S. crista.
◦ Cultural characteristics: small, rubbery (S.
sanguis) or non-adherent (S. oralis and S. mitis)
colonies on MSA.
◦ Main intraoral sites and infections: mainly dental
plaque; tongue and cheek; possibly dental caries;
infective endocarditis (except S. mitis).

Anaerobic streptococci (genus Peptostreptococcus)

Genus Stomatococcus
◦ Main species: Peptostreptococcus anaerobius; P. micros; P.
magnus.
◦ strict anaerobes, slow-growing, usually non-haemolytic.
◦ Main intraoral sites and infections: teeth, especially
carious dentin, periodontal and dentoalveolar abscesses in
mixed culture.
◦ Main species: Stomatococcus (formerly Micrococcus)
mucilagenosus.
◦ coagulase-negative, facultative anaerobes.
◦ Main intraoral sites and infections: tongue mainly, gingival
crevice; not a major opportunist pathogen.

Common isolates from dental plaque and
include
◦
◦
◦
◦
Genus
Genus
Genus
Genus
Actinomycetes
Lactobacilli
Eubacteria
Propionibacteria.

Genus Actinomyces
◦
◦
◦
◦
◦
Gram+ pleomorphic rods
The most important human pathogen is A. israelii.
ferments glucose
strict or facultative anaerobes.
Main intraoral sites and infections:
 Actinomyces odontolyticus, earliest stages of enamel
demineralization + caries progression
 A. naeslundii implicated in root surface caries and
gingivitis;
 A. israelii is an opportunist pathogen causing
cervicofacial and ileocaecal actinomycosis
 Actinomyces gerencseriae and A. georgiae: minor
components of healthy gingival flora.

Genus Lactobacillus
◦ Gram+ bacilli
◦ Main species: Lactobacillus casei; L. fermantum, L.
acidophilus; (others include L. salivarius, L. rhamnosus).
◦ Cultural characteristics: catalase-negative,
microaerophilic
◦ Main intraoral sites and infections:





Common oral inhabitants
< 1% of the oral flora
Dental plaque
advancing front of dental caries
lvls of salivary lactobacilli correlate with intake of dietary
carbohydrates (cariogenic potential)

Genus Eubacterium
◦ Gram-variable rods or filaments.
◦ Main species: Eubacterium brachy; E. timidum; E.
nodatum; E. saphenum.
◦ obligatory anaerobes
◦ Main intraoral sites and infections:
- dental plaque and calculus
- implicated in caries and periodontal disease
- comprise over 50% of the anaerobes of
periodontal pockets
- E. yurii is involved in ‘corn-cob’ formation in
dental plaque

Rothia dentocariosa
◦ a Gram-positive branching filament
◦ strict aerobe
◦ plaque + isolated from infective endocarditis.

Bifidobacterium dentium
◦
◦
◦
◦
Gram-positive
strict anaerobe
isolated from plaque
role in disease is unclear.

Genus Neisseria
◦
◦
◦
◦
◦

Gram- diplococci.
Main species: Neisseria subflava; N. mucosa; N. sicca.
asaccharolytic + non-polysaccharide producing
facultative anaerobes.
Main intraoral sites and infections:
 isolated in low numbers from tongue, saliva, oral mucosa
and early plaque
 consume oxygen in early stages of plaque formation
 provide conditions conducive for the growth of anaerobes
 rarely associated with disease.
Genus Veillonella

Genus Veillonella
Small, Gram-negative cocci.
Main species: Veillonella parvula; V. dispar; V. atypica.
strict anaerobes
Lack glucokinase and fructokinase and hence unable
to metabolize carbohydrates
◦ use lactate produced by other bacteria + raise the pH
of plaque
◦ beneficial in relation to dental caries.
◦ Intraoral sites/infections:
◦
◦
◦
◦
 isolated from most surfaces - tongue, saliva and plaque.
 No association with disease.




Genus
Genus
Genus
Genus
Haemophilus
Actinobacillus
Eikenella
Capnocytophagia

Genus Haemophilus
◦ Gram-negative coccobacilli.
◦ Main species: Haemophilus parainfluenzae; H. segnis;
H. aphrophilus; H. haemolyticus; H. parahaemolyticus.
◦ facultative anaerobes
◦ requires haemin (X factor) and nicotinamide adenine
dinucleotide (V factor) for growth.
◦ Main intraoral sites/infections:




dental plaque, saliva and mucosae
dentoalveolar infections
acute sialadenitis
infective endocarditis.

Genus Actinobacillus
◦ Gram-negative coccobacilli
◦ microaerophilic or capnophilic (carbon dioxide-dependent).
◦ Main species: Actinobacillus actinomycetemcomitans
◦ fimbriae
◦ many virulence factors: leucotoxin, collagenase,
protease that cleaves IgG.
◦ Main intraoral sites and infections:
 periodontal pockets -- aggressive forms of
periodontal disease (e.g. localised and generalised
aggressive periodontitis).

Genus Eikenella
◦
◦
◦
◦
◦
◦
Gram-negative coccobacilli.
Main species: Eikenella corrodens.
factor X-dependent
Microaerophilic
corroding colonies on blood agar.
Main intraoral sites and infections:




dental plaque
dentoalveolar abscesses
infective endocarditis
some forms of chronic periodontitis.

Genus Capnocytophagia
◦ Carbon dioxide-dependent, Gram-negative fusiform
rods with ‘gliding’ motility.
◦ Main species: Capnocytophaga gingivalis; C.
sputigena; C. ochracea; C. granulosa; C. haemolytica.
◦ capnophilic, medium-sized colonies with an irregular
spreading edge.
◦ Main intraoral sites and infections:




Plaque, mucosal surfaces, saliva
infections in immunocompromised
destructive periodontal
Some produce IgA1 protease.

Genus Porphyromonas
Gram-negative rods, non-motile
six serotypes based on capsular polysaccharides (K antigen)
asaccharolytic.
Main species: Porphyromonas gingivalis; P. endodontalis; P.
catoniae.
◦ strict anaerobes, require vitamin K and haemin for growth.
◦ Main intraoral sites and infections:
◦
◦
◦
◦
 gingival crevice and subgingival plaque
 chronic periodontitis and dentoalveolar abscess
 P. gingivalis - highly virulent (prod of haemolysin, collagendegrading)
 fimbriae helps adhesion.
 Porphyromonas endodontalis - recovered from infected root
canals.

Genus Prevotella
◦ Gram-negative rods, non-motile
◦ moderately asaccharolytic
◦ Main species:
- pigmented species include Prevotella intermedia; P.
nigrescens; P. loeschii; P. corporis; P. melaninogenica;
- Non-pigmented species include P. buccae; P. oralis; P.
oris; P. oulora; P. veroralis; P. dentalis
◦ Strict anaerobes, req vitamin K and haemin for growth.
◦ Main intraoral sites and infections:
 periodontal pockets, dental plaque
 chronic periodontitis and dentoalveolar abscess.

Genus Fusobacterium
◦ Slender, cigar-shaped
◦ Gram-negative rods with rounded ends
◦ Main species: Fusobacterium nucleatum; F. alocis;
F. sulci; F. periodonticum.
◦ often asaccharolytic
◦ strict anaerobes
◦ usually non-haemolytic;

Genus Fusobacterium
◦ ****F. nucleatum can produce ammonia + hydrogen
sulphide from cysteine and methionine and is
implicated as an odorigenic organism in halitosis.
◦ Main intraoral sites and infections:
 most common isolate is F. nucleatum
 normal gingival crevice, tonsils (F. alocis and F. sulci)
or periodontal infections (F. periodonticum)
 acute ulcerative gingivitis, dentoalveolar abscess.

Genus Leptotrichia
◦
◦
◦
◦
Gram-negative filaments
Main species: Leptotrichia buccalis.
strict anaerobes
Main intraoral sites and infections: dental plaque.
No known disease association.

Genus Wolinella
◦
◦
◦
◦
◦
Gram-negative curved bacilli
motile by polar flagella.
Main species: Wolinella succinogenes
strict anaerobe.
Main intraoral sites and infections: gingival crevice.
Possible involvement in destructive periodontal
disease.

Genus Selenomonas
◦ Gram-negative curved cells with tufts of
flagella.
◦ Main species: Selenomonas sputigena; S.
noxia; S. flueggei; S. inflexi; S. diane.
◦ strict anaerobe.
◦ Main intraoral sites and infections:
gingival crevice. No known disease
association.

Genus Treponema
◦ Motile Gram-negative helical cells, in three main sizes
◦ Main species: Treponema denticola; T. macrodentium; T.
skoliodontium; T. socranskii; T. maltophilum; T.
amylovarum; T. vincentii.
◦ all = strict anaerobes
◦ Main intraoral sites and infections:
 T. denticola - proteolytic than others
 proline aminopeptidase and and arginine-specific protease
 degrades collagen and gelatin. Found in the gingival crevice;
 associated w/ ANUG + destructive periodontal disease.

Dental Caries
◦ Mutans streptococci
◦ Lactobacillus spp.
 involved more in the progression of the
deep enamel lesion (rather than the
initiation)
 pioneer organisms in the advancing
◦ Actinomyces spp.
 root surface caries

Periodontal Microbes

Dentoalveolar abscess

Supporitive Osteomyelitis of the Jaws
◦ Anaerobes are the most common isolates –
 Bacteroides
 Prevotella
 Porphyromonas spp.
 Fusobacteria
 Anaerobic streptococci
 rarely enterobacteria present
◦ NOTE: Staphylococcus aureus MC osteomyelitis in
long bones
Oral Bacteroides
Pen
Fubsobacteria Anaerobic Cocci Alph-Strep
15-30
6
4
0
Erythromycin
0
85
18
0
Clinda
4
0
2
0
Metro
0
0
24
100
10
0
6
18
Cephalexin





Brooks GF, Butel JS, Ornston LN, editors: Jawetz,
Melnick and Aldenberg's medical microbiology, ed
19, Norwalk, Conn, 1991, Appleton & Lange
Samaranayake, Lakshman P. Samaranayake.
Essential Microbiology for Dentistry, 2nd Edition.
Elsevier, 2001. 31.2
Sanjiv Harpavat Microcards Lippincott, Williams and
Wilkins 2002
Peterson, LJ Microbiology of the Head and Neck.
OMFS Surg Clin. 3:255, 1991
Ellis E, Hupp. Contemporary Oral and Maxillofacial
Surgery 3rd ed.