Transcript The Staphylococci

The Staphylococci
Morphology & Identification
(-)
(+)
 Gram positive
 Facultative anaerobes
 Grape like-clusters
 Catalase positive
 Major components of
normal flora
 skin
 nose
Catalase test（过氧化氢
Staphylococcus aureus
Antigenic Structure
Pathogenesis
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Fc receptor
immunoglobulin
PHAGOCYTE
Protein A
BACTERIUM
Catalase
Coagulase
Hyaluronidase and Lipase
Hemolysin or sphingomyelinase C
Leukocidin
Exfoliative Toxin
Toxic Shock Syndrome Toxin
(superantigen)
Enterotoxins
Pathogenesis of staphylococcal infections
Stye:麦粒肿
Carbuncle:痈
Impetigo：脓疱疮
Suppurative
• Skin
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Furuncle; Protein A, Leukocidin, Hemolysin
Stye; lipase
Impetigo; contagious
Epidermal necrolysis
Exfoliative Dermatitis (6,7,8); Exfoliative toxin
Mastitis
Abscess (deep tissue); granulation; coagulase, hyaluronidase (burn, wound)
• Systemic
Bactermia (from abscess, wound, burn) , Osteomyelitis (tibia) ,Pneumonia
• Food poisoning
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not a human infection
food contaminated from humans
– growth
– enterotoxin
onset and recovery both occur within few hours
Vomiting/ nausea/ diarrhea/ abdominal /pain
• Toxic shock syndrome
• babies
– scalded skin syndrome
* Exfoliatin
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fever
scarlatiniform rash
desquamation
vomiting
diarrhea
myalgias
Infections associated with indwelling devices
Laboratory
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A. Direct examination; Gram Stain
B. Primary media; BAP
C. Differential Tests.
Mannitol Salts
Coagulase
DNase
D. Phage typing
E. Antibiotic Sensitivity (plasmid,
B lactamase) : penicillin
/methicillin/vancomycin
Lysostaphin test
Staphylococcus
Micrococcus
API STAPH Kit
Summary Figure (Identification Scheme)
Note: Strep. viridans
are alpha hemolytic and
negative for all the tests
below
GRAM POSITIVE COCCI
Catalase
Streptococcus (pairs & chains)
+
Staphylococcus (Clusters)
Coagulase
+
S. aureus
&hemolytic
mannitol
yellow
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Hemolysis
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S. epidermidis
nonhem olytic (usua lly)
mannitol
(2)
white
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BETA: Bacitracin
S .pyogenes (group A)
+
CAMP/Hippurate
+
S. agalactiae (group B)
ALPHA: Optochin/Bile Solubility
GAMMA: Bile Es culin
+
S. pneumoniae
+ 6.5% NaCl +
Group D*
Enterococcus
Bile Esc ulin
NaCl
Group D*
+ 6.5%
Non-Enterococcus
(*can also be beta or alpha hemolytic)
Staphylococcus epidermidis
• major component skin flora
• opportunistic infections
– less common than S.aureus
• nosocomial infections
– heart valves
• Identification
– Non-hemolytic (sheep blood agar)
– Does not ferment mannitol
– Non-pigmented
– Coagulase-negative
Staphylococcus saprophyticus
• urinary tract infections
• coagulase-negative
– not differentiated from S. epidermidis
The Streptococcus
Streptococcus
Morphology & Identification
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facultative anaerobe
Gram-positive
Chains or pairs
Catalase negative
(staphylococci are catalase positive)
Cell surface structure of S pyogenes
and extracellular substances
•Lancefield groups
*one or more species per group
*surface antigens: M, T, R
groupable streptococci
•A, B and D
–most important
•C, G, F
–Rare
Non-groupable
•S. pneumoniae
–pneumonia
•viridans streptococci
–e.g. S. mutans
*dental
caries
Lipoteichoic Acid and F-protein
lipoteichoic acid
F-protein
fibronectin
epithelial cells
M protein
• major target
– natural immunity
• strain variation
– antigenicity
• re-infection
– occurs with different strain
M protein
IMMUNE
Complement
IgG
r
r
r
M protein
NON-IMMUNE
peptidoglycan
fibrinogen
r
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r
Toxins & Enzymes
Hemolysis
alpha
beta
gamma
Classofication of Streptococci of Particular Medical Interest
Pathogenesis of S pyogenes infections.
S. pyogenes (Group A) -suppurative
• affect all ages peak incidence at
5-15 years of age
• non-invasive
– pharyngitis
– skin infection, impetigo
• invasive bacteremia
– toxic shock-like syndrome
– "flesh eating" bacteria
– pyrogenic toxin
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Rheumatic fever -etiology
Scarlet fever
 M protein
rash
– cross-reacts heart myosin
– autoimmunity
erythrogenic toxin
 cell wall antigens
rheumatic fever
– poorly digested in vivo
inflammatory disease
– persist indefinitely
life threatening
Post-infectious diagnosis (serology)
chronic sequalae
• antibodies to streptolysin O
fever
• important if delayed clinical sequelae
Heart
occur
Joints
rheumatic NOT rheumatoid arthritis
• superantigen
Acute glomerulonephritis
• T cell mitogen
• activates immune
immune complex disease of kidney
system
Group B streptococcus identification
• neonatal meningitis
• septicemia
• transmission
– vaginal flora
•  hemolysis
• hippurate hydrolysis
• CAMP reaction
– increases  hemolysis of S. aureus
Group D streptococcus
• Growth on bile esculin agar
– black precipitate
• 6.5% saline
• grow
– enterococci
• no growth
– non-enterococci
Enterococci
• distantly related to other streptococci
• genus Enterococcus
• gut flora
– urinary tract infection
• fecal contamination
– opportunistic infections
• particularly endocarditis
• most common E. (S.) faecalis
• resistant to many antibiotics
– including vancomycin
• terminal D-ala replaced by D-lactate
Viridans streptococci
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diverse species
oral
dental caries
 hemolytic and negative for other tests
non-groupable.
includes S. mutans
– endocarditis
– tooth extraction
Streptococcus pneumoniae
S. pneumoniae - diplococci
• capsule:
• pneumolysin:
• Surface protein
adhesinand secretory IgA
protease.
• Teichoic acid and the
Peptidoglycan fragment,
phosphorylchorine .
• leading cause pneumonia
– particularly young and old
– after damage to upper
respiratory tract
*e.g. following viral infection
• bacteremia
• meningitis
• middle ear infections (otitis media)
Summary Figure (Identification Scheme)
Note: Strep. viridans
are alpha hemolytic and
negative for all the tests
below
GRAM POSITIVE COCCI
Catalase
Streptococcus (pairs & chains)
+
Staphylococcus (Clusters)
Coagulase
+
S. aureus
&hemolytic
mannitol
yellow
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Hemolysis
•
S. epidermidis
nonhem olytic (usua lly)
mannitol
(2)
white
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BETA: Bacitracin
S .pyogenes (group A)
+
CAMP/Hippurate
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S. agalactiae (group B)
ALPHA: Optochin/Bile Solubility
GAMMA: Bile Es culin
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S. pneumoniae
+ 6.5% NaCl +
Group D*
Enterococcus
Bile Esc ulin
NaCl
Group D*
+ 6.5%
Non-Enterococcus
(*can also be beta or alpha hemolytic)
Bile solubility test
Streptex antiserum
optochin sensitive
Not optochin sensitive
Quellung reaction
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using antisera
capsule "fixed"
visible microscopically
Latex agglutination - streptococci
Prevention and Treatment
• Immunity ; 14 capsule types mixed
vaccine
• Most strains susceptible to
penicillin , but resistance is
common
Neisseria
• Gram negative
• diplococci (pairs of
cocci)
• oxidase positive
• Culture: 5-10% CO2
• Thayer Martin.
– selective
– chocolate agar
* heated blood
N. meningitidis
N. gonorrhoeae
Virulence Factors
Similar, but –
Differences
in utilization
LPS
LPS
Capsule
IgA protease
Hemolysin
IgA protease
PILI
Opacity (OPA) proteins
Outer Membrane Proteins
PILI
Opacity (OPA) proteins
Outer Membrane Proteins
X
NO capsule
NO hemolysin
Neisseria gonorrhoeae
• After 2-14 days
•Found only in man
• Gonorrhea: second most common venereal
disease
Gram stain of pure culture
Urethral exudate
Using the Gram stain in patient specimens, the organisms are most often
observed in polymorphonuclear leukocytes
Neisseria gonorrhoeae
Pili = key in anchorage of
organisms
to mucosal epithelium.
Nonpiliated gonococci are avirulent
OUTER MEMBRANE PROTEINS
Porin proteins (Por) = prevent phagolysosome fusion & allow
intracellular survival [ also called protein I]
Opacity proteins (Opa) = binding of organisms to epithelium
[also called protein II]
Reduction-modifiable proteins (Rmp) = protection against
bactericidal antibodies [ also called protein III]
Urethritis
Bartholin’s Duct
Disseminated gonococcal infection
(DGI).
Fever, polyarthritis
(or monoarticular septic arthritis),
and/or dermatitis
(pustules on a hemorrhagic base).
Purulent conjunctivitis/Ophthalmia neonatorum Infection in
newborns during vaginal delivery
Smear
• polymorphonuclear cell
• Gram negative cocci
many in cells
• Culture
Antibiotic therapy
•  lactamase-resistant cephalosporin
– e.g. ceftriaxone
• resistant strains
– common
– produce  lactamases
– destroy penicillin
N. meningitidis
(the "meningococcus")
Neisseria
meningitidis
• resides in man only
• usually sporadic cases
– mostly young
children
• outbreaks
– adults
– crowded conditions
* e.g. army
barracks
Upper respiratory
tract infection
– adhesion pili
Meningococcal
meninigitis
• 1-4 days
• Second most common
meningitis
– pneumococcus,
most common
• Fatal if untreated
• Responds well to
antibiotic therapy
– penicillin
Bloodstream
Brain
Prevention
Diagnosis
• spinal fluid
– Gram negative
diplococci
within
polymorphonuclear cells
– meningococcal
antigens
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Culture
– Thayer Martin agar
• capsule
– inhibit phagocytosis
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anti-capsular antibodies
– stop infection
• antigenic variation
– serogroups
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vaccine
– multiple serogroups