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31 Cards in this Set
- Front
- Back
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group A strep
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Strep pyogenes
beta hemolytic suppurative (pus forming) diseases - pharyngitis - impetigo - cellultis/bacteremia/necrotizing fascitis - scarlet fever non suppurative diseases - rheumatic fever - acute glomerulonephritis - PANDAs |
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pharyngitis in Group A strep pyogenes
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5-15 years of age
tender LNs fver diagnosed with culture or antigen tests |
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impetigo in Group A strep pyogenes
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colonnize unbroken
exposed areas weepy patches of red skin highly contagious |
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Classification
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B-hemolytic streptoccoci: Groups A, B, C & G
- lancefield grouping a-hemolytic strep: Strep viridans group & Strep pneumoniae gamma-hemolytic strep: non-hemolytic; Group D strep & enterococci |
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cellulitis/bacteremia/necrotizing fascitis in group A strep pyogenes
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cellulitis: wound/burn infections
necrotizing fascitis: invasive group A streptoccoal disease - "flesh eating bacteria" - 20% mortality rate - treatmnet : surgicaldebridement, penicillin, clindamycin & IVIG - toxic shock syndrome |
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scarlet fever in group A strep pyogenes
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associated with streptococcal pyrogenic exotoxin : SPE
rash begins on chest, moves to face : small papular rash, feels like sandpaper pastia's lines : folds of skin |
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Rheumatic fever in group A strep
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associated with untreated throat infections of group A strep
rheumatogenic strains have certain M types that produce cross reactive antibodies to heart tissue |
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acute glomerulonephritis iin group A strep
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associated with previous pyoderma orthroat infections by group A strep
cross reactive antibodies/immune complexes possible disease mechanisms |
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PANDAs
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TICS
TOURETTES ocd |
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virulence factors of strep A
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M protein is main virulence factor
- over 80 diff types - Ab against specific M type is protective multiple adhesins allow adherance to epithelial cells some may actually invade epithelial cells negatively charged hyaluronic acid capsule inhibits phagocytosis M protein inhibits complement attachment and phago multiple production of toxins - streptolysin O & S; streptococcal pyrogenic exotoxins: superantigens (esp important for necrotizing fascitis & invasive disease) |
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epidemiology of group A
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asymptomatic carriers
changing epidemiology throughout 20th century: invasive group A strep disease on upswing specific M types for speciffic diseases |
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treatment for strep A
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penicillin
full treatment needed to suppress post streptococcal sequellae - rheumatic fever & glomerulonephritis |
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gropu B streptococci
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strep agalactiae
beta hemolytic major cause of disease n neonatal & perinatal periods UTIs other types of disease in compromised pts |
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group B early onset
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organism acquired through
- ascending infection in utero before delivery - ruptured fetal membranes - passage through a birth canal that is colonized about 50% will become colonized; 1-2% have disease become ill within first 12-20 hours of birth - meningitis, bacteremia, pneumoniae |
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group B late onset
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acquired from mother, visitors or other health care givers
average 3-4 weeks after birth meningitis most common presentation |
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group B treatment
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penicillin +/- aminoglycoside
cAMP rxn : diagnostic for group B strep ; older test used in clinical microbiology |
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group C, F & G streptococci
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Beta hemolytic
mostly cause disease in compromised host; deep abscesses, bacteremia believed to cause pharyngitis treatment: penicillin |
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strep viridans group
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alpha hemolytic
normal inhabitant of upper resp tract 30-40% of all cases of subacute bacterial endocarditis oropharynx associated with dental procedures; compromised pts treatment: some strains resistant to penicillin; need susceptibility performed by lab |
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Streptococcus pneumoniae
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alpha hemolytic
major cause of community acquired pneumoniae major cause of adult meningitis; with Haemophilus influenze vaccine in use, now becoming most common cause of meningitis in infant & toddlers otitis media, sinusitis bacteremia |
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strep pneumoniae virulence factors
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polysaccharide capsule
- more than 80 antigenically diff types have been describd; with some being more virulent - anti capsular antibodies are protective incidence of pneumonia increases in those with defects in upper resp tract clearance mechanisms - smokers - asthma - chronic bronchitits |
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clinical microbiology of strep pneumoniae
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optichin test
is susceptible : zone of inhibition around disk other alpha hemolytic strep are resistant: grow up to disk |
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vaccin & treatment for strep pneumoniae
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vaccine: contains capsular polysaccharide from each of 23 serotypes most frequently associated with disease
treatment - penicillin resistnace problem in treating severe disease, susceptibility testing needed - resistance to erythromycin is also increasing - resistnace to fluoroquinolones is low |
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enterococci-gamma-hemolytic
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human infections: enterococcus faecalis, E. faecium
- rarely: E. casseliflavus, E. avium, E. durans, and E. gallinarum normal residents of GI tract & vagina |
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diseases from enterococci
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UTIs
bacteremia endocarditis |
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enterococci risk factors
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compromised pt or previous therapy with antibiotics which have no activity against enterococci (cephalosporins)
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problems associated with enterococcal disease
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Antbiotic resistance **
relative intrinsic R to macrolides & cephalosporins -increasing R to aminoglycosides & penicillins vancomycin R streains : VRE ; very difficult to treat 2 new Abs, Synercid & Linezolid, have been recently FDA approved for use against VRE major convern: VRE is known (under lab conditions) to pass vancomycin R to Staph aureus. S. aureus containing vancomycin R genes from enterococci have recently been isolated |
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group D non enterococci
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Streptococcus bovis
non hemolytic normal inhabitants of GI tract S. bovis endocarditis or bacteremia associated with colonic cancer treatment: most strains susceptible to penicillin |
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Lancefielld grouping of beta hemolytic strep
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group A: rhamnose-N-acetylglucosamine polysaccharide
- Streptococcus pyogenes Group B: Rhamnose-glucosamine polysaccharide - Strep agalactiae difference is antigen on cell wall : group specific carbs |
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2 most important factors in impetigo
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climate (summer months) & hygiene
tropical areas & infrequent hygiene |
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PANDAs
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pediatric autoimmune neuropsychiatric disorders associated with strep infections
- Sydenham's chorea: can't control extremity movement - Tourettes syndrome, tics, OCD - immune sequelae of GAS: antibodies attack basal ganglia |
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penicillin R strep
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viridans
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