Transcript Skin

Pyogenic Coccus
The Staphylococci
Morphology & Identification
 Gram positive
 Facultative anaerobes
 Grape like-clusters
 Catalase positive
 Major components of normal flora
 skin
 nose
Gram Positive cocci - staphylococci
Pus
Catalase test（过氧化氢酶）
(-)
(+)
Pathogenesis & Immunity of
Staphylococcus aureus
Antigenic Structure
Protein A inhibits
phagocytosis
Fc receptor
immunoglobulin
PHAGOCYTE
Protein A
BACTERIUM
Toxins & Enzymes
• Catalase
• Coagulase
• Hyaluronidase and Lipase
•
•
•
•
•
Hemolysin or sphingomyelinase C
Leukocidin
Exfoliative Toxin
Toxic Shock Syndrome Toxin (superantigen)
Enterotoxins
Pathogenesis
Pathogenesis of staphylococcal infections
Stye:麦粒肿
Carbuncle:痈
Impetigo：脓疱疮
Infections associated with indwelling
devices
Superantigens and the non-specific
stimulation of T cells
Clinical Findings- Suppurative
• A. (Skin)
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)
• B. Systemic : Bactermia (from abscess, wound,
burn) , Osteomyelitis (tibia) ,Pneumonia
Clinical Findings- Food
poisoning
• 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
• fever
• scarlatinifor
m rash
• desquamatio
n
• vomiting
• diarrhea
S. aureus
• babies
–scalded skin
syndrome
* exfoliatin
Pseudomembranous Colitis
Laboratory
•
•
•
1.
2.
3.
•
•
•
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
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
-
Hemolysis
•
S. epidermidis
nonhem olytic (usua lly)
mannitol
(2)
white
•
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)
S. aureus on BAP
Mannitol Salt Agar
DNase test
0.1% Toluidine blue O
(+): Pink
1N HCl (+) :
S. aureus on potassium tellurite agar
Lysostaphin test
Staphylococcus
Micrococcus
API STAPH Kit
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
•
•
•
•
facultative anaerobe
Gram-positive
Chains or pairs
Catalase negative
(staphylococci are catalase positive)
Cell surface structure of S pyogenes
and extracellular substances
S. pyogenes
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
r
r
Capsules
• Anti-phagocytic
– mucoid strains
• Streptococci
• Lancefield groups
*one or more species per group
*surface antigens
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
Toxins & Enzymes
Hemolysis
alpha
beta
gamma
Classofication of Streptococci of Particular Medical
Interest
Pathogenesis of S pyogenes infections.
• Group A streptococcal infections affect
all ages peak incidence at 5-15 years of
age
S. pyogenes -suppurative
• non-invasive
– pharyngitis
– skin infection, impetigo
• invasive bacteremia
– toxic shock-like syndrome
– "flesh eating" bacteria
– pyrogenic toxin
Pyrogenic toxin
• superantigen
• T cell mitogen
• activates immune system
Scarlet fever
• rash
• erythrogenic toxin
non-suppurative
• rheumatic fever
– inflammatory disease
– life threatening
– chronic sequalae
• fever
• heart
• joints
• rheumatic NOT rheumatoid arthritis
Rheumatic fever -etiology
M protein
– cross-reacts heart myosin
– autoimmunity
cell wall antigens
– poorly digested in vivo
– persist indefinitely
Rheumatic fever
Acute glomerulonephritis
• immune complex disease of kidney
Group B streptococcus
• neonatal meningitis
• septicemia
• transmission
– vaginal flora
Group B streptococcus identification
•  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
Enterococci
• resistant to many antibiotics
– including vancomycin
• terminal D-ala replaced by D-lactate
Viridans streptococci
•
•
•
•
•
•
diverse species
oral
dental caries
 hemolytic and negative for other tests
non-groupable.
includes S. mutans
– endocarditis
– tooth extraction
Diagnostic Laboratory Test
Post-infectious diagnosis
(serology)
• antibodies to streptolysin O
• important if delayed clinical
sequelae occur
Serotyping
M
T
R
S. pneumoniae - diplococci
S. pneumoniae Virulence
factors
• a. capsule: It is antiphagocytic, inhibiting entrapment
and phagocytosis where type-specific opsonic antibody
is absent. Non-capsulate mutants are avirulent in
experimental animals.
• b. pneumolysin: It suppresses phagocytic oxidative
burst. It is a membrane-damaging toxin. Thus it can
destroys red blood cells and possibly ciliated
epithelial cells.
• c. Surface protein adhesinand secretory IgA
protease: The biologic effects are to help
S.pneumoniae for the colonization and migration.
• d.Teichoic acid and the Peptidoglycan fragment,
phosphorylchorine : They can mediate the
mobilization of inflammatory cells to the focus of
infection
and
cause
the
tissue
Capsule
• prominent
– virulent strains
• anti-phagocytic
• carbohydrate antigens
– vary among strains
• immunity
– serotype specific
• vaccine contains multiple
serotypes
• only for susceptible population
clinic finding
• 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)
(-)
(+)
(Bile solubility test)
Autolysis - identification
autolysin
teichoic acid
-choline
peptidoglycan
cell
membrane
lipoteichoic acid
Bile
Identification
Not optochin sensitive
optochin sensitive
Quellung reaction
• using antisera
• capsule "fixed"
• visible microscopically
Streptex antiserum
Latex agglutination - streptococci
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
-
Hemolysis
•
S. epidermidis
nonhem olytic (usua lly)
mannitol
(2)
white
•
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)
Prevention and Treatment
• Immunity ; 14 capsule types
mixed vaccine
• Most strains susceptible to
penicillin , but resistance is
common
NEISSERIA
Neisseria gonorrhoeae
Neisseria
• Gram negative
• diplococci (pairs of cocci)
• oxidase positive
• culture
• Thayer Martin.
– selective
– chocolate agar
* heated blood (brown)
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
N. gonorrhoeae
the "gonococcus"
• After 2-14 days
•Found only in man
• Gonorrhea: second most
common venereal disease
Neisseria gonorrhoeae
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
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]
Neisseria gonorrhoeae
Symptomatic infections are notably PURULENT
Urethritis
Neisseria gonorrhoeae
Symptomatic infections are notably PURULENT
Bartholin’s Duct
Neisseria gonorrhoeae
Purulent conjunctivitis
Ophthalmia neonatorum
Infection in newborns
during vaginal delivery
Neisseria gonorrhoeae
Disseminated gonococcal infection (DGI).
Fever, polyarthritis
(or monoarticular septic arthritis),
and/or dermatitis
(pustules on a hemorrhagic base).
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")
N. meningitidis
• resides in man only
• usually sporadic cases
– mostly young children
• outbreaks
– adults
– crowded conditions
* e.g. army barracks
Neisseria meningitidis
upper respiratory tract infection
– adhesion pili
bloodstream
brain
Meningococcal meninigitis
• 1-4 days
• Second most common meningitis
– pneumococcus, most common
• Fatal if untreated
• Responds well to antibiotic
therapy
– penicillin
Laboratory Diagnosis
• spinal fluid
– Gram negative diplococci
within polymorphonuclear cells
– meningococcal antigens
•
Culture
– Thayer Martin agar
Prevention - Capsule
• capsule
– inhibit phagocytosis
• anti-capsular antibodies
– stop infection
• antigenic variation
– serogroups
• vaccine
– multiple serogroups