The Staphylococci123.5 KB
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Staphylococcus-StreptococcusEnterococcus
Gr + cocci
~ 21 genera
Common features
Spherical shape
Gram stain reaction
Absence of endospores
Catalase activity
Catalase positive genera
subdividing
Staphylococcus
Micrococcus
Stomatococcus
Alloiococcus
Catalase negative genera
Streptococcus
Enterococcus
Staphylococcus
Gram positive
Grow pattern
cluster of grapes
single cells, pairs,
short chains
Nonmotile
Aerobic or facultatively anaerobic
Catalase-positive
Grow in 10 % NaCl medium @ 18-40 o C
Most common Staph. causing diseases
S. aureus
S. epidermidis
S. saprophyticus
S. capitis
S. haemolyticus
Produce coagulase
Coagulase negative
staphylococcus
Micrococcus
Can be confused with CN staphs
Differ in that, they grow only aerobically
Resistant to lizostafin and furazolidone
Isolation of micrococcus in clinical samples
Contamination ?
Stomatococcus
Stomatococcus
mucilaginosus
Only species in this
genus
Infection in the
immunocompromised
host
Alloiococcus
Alloiococcus otitidis
Only species in this
genus
Aerobic Gr +
Disease??
Staphylococcus and their diseases
S. aureus
Toxin-mediated
Food poisoning
Toxic shock syndrome, scalded skin
syndrome
Cutaneous
Impetigo
Folliculitis
Furuncles
Carbuncles, wound infections
Staphylococcus and their diseases
S. aureus
Others
Bacteremia
Endocarditis,
Pneumoniae
Empyema
Osteomyelitis
Septic arthritis
Staphylococcus and their diseases
S. epidermidis
Bacteremia
Endocarditis,
Surgical wounds
Urinary tract infections
Opportunistic infections of catheters,
shunts, prostetic devices and peritoneal
dialysates
Staphylococcus and their diseases
S. saprophyticus
Urinary tract infections
Opportunistic infections
Resistant to novobiocin
Staphylococcus/physiology & structure
Capsule
Peptidoglycan
Teichoic acids
Protein A
Coagulase and other sutface proteins
Cytoplasmic membrane
Staphylococcus/capsule
Loose-fitting
Polysaccharide layer (slime layer)
In vitro
rare
Staphylococcus/peptidoglycan
Half of the cell wall
More rigide compared to Gr negatives
Endotoxin-like activity
Endogenous pyrogenes
Activation of complement
Production of int-1 from monocytes
Aggregation of polymorphonuclears
Staphylococcus/teichoic acids
Teichoic & lipoteichoic acid
Polysaccharide A in S. aureus
Polysaccharide B in S. epidermidis
Mediate the attachment of staphs to
mucosal surfaces
Poor immunogens (except when bound to
peptidoglycan)
Staphylococcus/protein A
The surface of most S. aureus is coated with
protein A (not CNS)
Affinity to bind Fc receptor of IgG1, IgG2 &
IgG4
prevents the antibodymediated immune clearence of the bacteria
Staphylococcus/coagulase & other surface
proteins
S. aureus clumping factor (bound
coagulase)
Collagen-binding protein
Elastin-binding protein
Fibronectin-binding protein
adherence to
host tissues
Staphylococcus/pathogenesis & immunity
Toxins
&
Enzymes
Staphylococcus/toxins
Alpha toxin
Beta toxin
Delta toxin
Gamma toxin & Panton-Valentine Leukocidin
Exfoliative toxins
Enterotoxins
Toxic shock syndrome toxin-1
Staphylococcus/toxins
a Toxin
important mediator of tissue
damage in staphylococcal
diseases
toxic for many cells (erythrocytes,
leukocytes, hepatocytes,..)
produced by most strains of
S. aureus
Staphylococcus/toxins
b Toxin
sphingomyelinase C
toxic for many cells
role in tissue destruction &
abscess formation
produced by most strains of
S. aureus
Staphylococcus/toxins
d Toxin
wide spectrum of cytolytic
activity
detergent-like activity
produced by most strains of
S. aureus
Staphylococcus/toxins
g Toxin & Panton-Valentine Leukocidin
composed of two polypeptide
chains
toxic for many cells
Staphylococcus/toxins
Exfoliative toxins
staphylococcal scalded
skin syndrome (SSSS)
exfoliative dermatitis
two types: ETA & ETB
produced by 5 to 10 %
of all S. aureus strains
Staphylococcus/toxins
Enterotoxins
8 serologically distinct
enterotoxins exist (A-E, G-I)
stable to heating
resistant to
gastric & jejunal enzymes
produced by 30 to 50 %
of all S. aureus strains
are superantigens
Staphylococcus/toxins
Toxic shock syndrome toxin-1
heat & proteolysis resistant
all S. aureus responsible for
menstruation-associated TSS produce
TSST-1
50 % of the strains responsible for other
forms of TSS produce TSST-1
superantigens
Staphylococcus/enzymes
Coagulase
Catalase
Hyaluronidase
Fibrinolysin
Lipases
Nuclease
Penicillinase
Staphylococcus/enzymes
Coagulase
S. aureus
2 forms
Bound
free
Staphylococcus/enzymes
Catalase
“All staphylococci produce catalase”
H2O2 (toxic)
H2O
O2
Staphylococcus/enzymes
Hyaluronidase
Hydrolyzes hyaluronic acids
facilitates the
spread of S.
aureus in tissues
> 90 % of S. aureus produce hyaluronidas
e
Staphylococcus/enzymes
Fibrinolysine
Staphylokinase
All S. aureus
Dissolve fibrine clots
Staphylococcus/enzymes
Lipases
Nuclease
All S. aureus & 30 % of the CNS produce several
different lipases
A marker for S. aureus
Penicillinase (b-lactamase)
Staphylococcus/IDENTIFICATION
Microscopy
Culture:
Nutritionally enriched agar media with sheep blood
Selective agar media for S. aureus with 7.5 % NaCl +
mannitol
Aerobic and anaerobic
Large, smooth colonies
Identification
Positive coagulase, heat-stable nuclease, alkaline
phosphatase, mannitol ferment.
S. aureus
Streptococcus
Gram positive
Grow pattern
pairs, chains
Most species are facultatively anaerobes
Some grow only in atmosphere enhanced
with CO2
Nutritional requirements are complex
Blood, serum
“Catalase-negative”
Streptococcus
Classification is complicated
1.
2.
3.
3 different schemes are used
Lancefield groupings according to serologic
properties (A-H, K-M, O-V)
Hemolytic patterns: b, a & g hemolysis
Biochemical properties
Streptococci and their diseases
S. pyogenes (group
A)
Pharyngitis,
scarlet fever,
pyoderma,
erysipelas,
cellulitis,
necrotizing
fasciitis,
streptococcal toxic
shock syndrome,
bacteremia,
rheumatic fever,
glomerulonephritis
Streptococci and their diseases
S. agalactiae
(group B)
Neonatal
infections
(meningitis,
pneumoniae,
bacteremia)
Urinary tract
infections
Amnionitis,
Endometritis
Wound infections
Streptococcus pyogenes/physiology & structure
Spherical cocci
Form short (clinical specimen) or long chains
(liquid media)
Grow on enriched blood agar media
White colonies
1-2 mm with large zones
of b-hemolysis
Encapsulated strains mucoid
Basic structure in the cell wall is
peptidoglycan as Staphs
group spec. Ag
Streptococcus pyogenes/physiology & structure
Group specific carbohydrate
Within the cell wall
10 % of the dry weight
Is used to classify group A streptococci and
distinguish them from others
Streptococcus pyogenes/physiology & structure
Type specific proteins
M protein
major type-specific protein
associated with virulent streptococci
2 polypeptide chains
1.
2.
Highly conserved among all ggroup A streptococci
Responsible for the antigenic variability
>80 serotypes
T protein (trypsin-resistant)
secondary
Usefull when bacteria fail to express the M protein
Streptococcus pyogenes/physiology & structure
Other cell surface components
M-like proteins
Lipoteichoic acid
F protein
Capsule (hyaluronic acid)
Streptococcus pyogenes/Pathogenesis&Immunity
Virulence of S. pyogenes
The ability of the bacteria
to adhere to the surface of the host cells
Invade into the epithelial cells
Avoid opsonization & phagocytosis
Produce a variety of toxins & enzymes
Streptococcus pyogenes/Pathogenesis&Immunity
Pyrogenic exotoxins
(Streptococcal pyrogenic exotoxin, Spes)
Produced by lysogenic strains
Superantigens
Responsible for the streptococcal toxic
shock syndrome
Streptococcus pyogenes/Pathogenesis&Immunity
Streptolysin S & O
Streptolysine S
Streptolysine O
lyse erythrocytes
leukocytes
platelets
responsible for b-hem.
lyse erythrocytes
leukocytes
platelets
antibodies are formed
against
ASO test
Streptococcus pyogenes/Pathogenesis&Immunity
Streptokinases
Deoxyribonucleases
A&B
Lyse blood clots
Used in medicine
A to D
Depolymerase free DNA in pus
viscosity
reduce
C5a peptidase
Hyaluronidase,diphosphopyridine nucleotidase
Streptococcus pyogenes/IDENTIFICATION
Microscopy
Culture:
Proper collection of throat swab specimen
Nutritionally enriched agar media with sheep
blood
Selective media (media with “bactrim”)
Identification
Table 23-4
Streptococcus agalactiae (Group B)
The only species that carries the group B
antigen
physiology & structure
Gr + cocci
Short or long chains (indistinguishable from S. pyogenes)
Buttery colonies, narrow zone of b-hem.
Subdividing
The B antigen
group specific
Capsular polysaccharides
type-specific
C protein (surface protein)
Streptococcus agalactiae/IDENTIFICATION
Microscopy
Culture:
Readily grow on a nutritionally enriched medium
Large colonies
b-hemolysis may be absent
selective broth
medium with antibiotics
Identification
Preliminary identification
(+) CAMP test,
hydrolysis of
hippurate
Other beta-hemolytic streptococci
Group C, F and G are most commonly
associated with human disease
2 species of particular importance
S. anginosus
S. dysgalactiae
Viridans Streptococci
a-hemolytic and nonhemolytic streptococci
Produce green pigment on blood agar media
Require complex media supplemented with
blood products and inc. @ 5-10 % CO2 atmsp.
Streptococcus pneumoniae
Encapsulated, Gr + coccus
Lancet-shaped cells, in pairs or short chains
a-hemolytic
Can grow only on enriched media (with blood
products)
Catalase (-)
Capsule, classified accr. to polysaccharides
90 serotypes
Capsular polysaccharides are used in vaccines
Teichoic acid
C polysaccharide (CRP)
S. pneumoniae / diseases
Pneumoniae
Meningitis
Sinusitis
Otitis media
Bacteremia
Streptococcus pneumoniae/Pathogenesis&Immunity
The disease manifestations are caused primarily
by the host response to infection
Streptococcus pneumoniae/Pathogenesis&Immunity
Colonization & migration
S.pn colonizes the oropharynx
Can spread to the lungs, paranasal
sinuses, middle ear, blood stream
By means of:
Surface protein adhesins, secretory IgA
(sIgA) protease, pneumolysin
Streptococcus pneumoniae/Pathogenesis&Immunity
Tissue destruction
Mobilization of inflamatory cells
pneumococcal infections
characteristic of
Teichoic acid
Peptidoglycan fragments
Pneumolysin
H2O2 production
Phosphorylcholin
Phagocytic survival
Capsule
Pneumolysin mediated suppression of the
phagocytosis
Streptococcus pneumoniae/IDENTIFICATION
Microscopy
Culture:
Lancet-shaped, Gr (+) diplococci, unstained
capsule (Gram stain with “quellung” reaction)
Enriched supplemented medium with blood
Selective medium with gentamicin
Identification
Bile solubility test
Optochin
Enterococcus
Most frequently isolated & most commonly
responsible for human disease with
streptococcus among gram-positive cocci
“enteric cocci”
Possess the group D cell wall antigen
16 species in the genus
E. faecalis & E. faecium are most commonly
isolated
Enterococcus/physiology & structure
They can not be differentiated from S.
pneumoniae in microscope
Facultatively anaerobic
Optimal growth temp.= 35 oC (10oC to 45oC)
White, large colonies on blood agar (after 24h)
Nonhemolytic (or a or b-hemolysis)
Grow in the presence of
6.5 % NaCl, tolerate 40 % bile salts,
hydrolyse esculin
Enterococcus/Pathogenesis&Immunity
Are commensal with
limited potential for
causing disease
Do not possess toxins
Cannot avoid being
engulfed & killed by
phagocytic cells
BUT,
Cause
Serious
Disease
Enterococcus/Pathogenesis&Immunity
Virulence factors
Adhesive factors
Bacteriocins
Inherently resistant to many
antibiotics
Enterococcus/Clinical Diseases
Can cause life-threatening infections
One of the most feared nosocomial
pathogens
10% of all nos. infct.
Most commonly involved sites
Urinary tract
Blood stream
A sever complication: endocarditis( following
bacteremia)
Enterococcus/Laboratory diagnosis
Grow readily on nonselective media
Resemble S. pneum.
Differentiation
resistant to optochin
don’t dissolve when
exposed to bile
hydrolyze PYR
pyrolidonyl-b-naphthylamide