Streptococci Flashcards
what are some general characteristics of strep infections?
spreading of suppurative infections
-cellulitis, impetigo, erisypelas, GABHS
what are some post-strep hypersensitivity disease?
- rheumatic fever
- immune complex glomerulonephritis
Group A strep is associated with?
GABHS, beta hemolytic,
- S. pyogenes
- pharyngitis/post strep disease
Group B strep is associated with?
peri-natal sepsis/newborn, UTI
Viridans strep is associated with?
not one species
- alpha hemolytic,
- major cause of subacute bacterial endocarditis
beta hemolytic strep
- clear, complete hemolysis
- Pyogenes: Group A, bactracin sensitive
alpha hemolytic strep
green, partial hemolytic
- Pneumoniae
- Viridans
Pneumoniae strep
optochin sensitive
- bile soluble
- capsule-> quellung
Viridans strep
mutans, sanguis
- optochin resistant
- NOT bile soluble
- no capsule
streptococcus mutans
major cause of dental caries
gamma-hemolytic strep
Enterococcus
-E. faecalis
E. faecium
what are the virulence factors of strep?
- cell wall polysaccharides
- capsules (M proteins)-> prevent phagocytosis
- enzymes: streptokinase, streptolysin O,S
enzymes streptokinase, streptolysin O,S help strep to do what?
contribute ability to spread through tissues (cellulitis)
what does strep erythrogenic toxin do?
skin rash
what is the hosts response to strep?
antibodies to both capsular antigens and exotoxins
- M protein of many subtypes is antiphagocytic
- antibodies help in preventing recurrent pharyngeal infections in some
antibodies to which strep can cross react to cause rheumatic fever?
Group A
- S. pyogenes
- deposition of immune complexes in kidney-> poststreptococcal glomerulonephritis
What infections are associated with Group A strep?
GABHS or GAS
- acute pharyngitis/UPT-> redness, edema, pain, fever, chills
- punctate abscesses in tonsillar crypts
- peritonsillar, retropharyngeal abscess formation
Scarlet fever
- ages 3-15, erythrogenic toxin, violaceous red rash on trunk
- strawberry tongue
- associated with poststreptococcal sequelae
what are some post-streptococcal sequelae?
post-streptococcal glomerulonephritis:
rheumatic fever
post-streptococcal glomerulonephritis
1-2 week after strep
- self-limited
- immune-complex mediated
- can see signs of acute renal failure->oliguria, hematuria, hypertension
rheumatic fever
weeks-months and beyond
- worse with repeated infections
- acute: fever, joint disease, myocardial and valvular disease
- corresponds to streptolysin O titers in blood
- NO bacteria present (autoimmune cross reactivity)
- if chronic: long standing damage to mitral and aortic heart valves
strep infections: cellulitis, pyoderma
redness, swelling and pain
- less localized than staph infections
- abscesses are rare, and so are necrotizing fasciitis
strep infections: impetigo
contagious skin infection in kids involving horny layers of skin
- could be due to staph
- can be due to GABHS (S. pyogenes) with post-strep sequelae
strep infections: erysipelas
- groups A/C
- warm climates
- erythematous skin involvement without suppuration
necrotizing fasciitis, “flesh eating disease”
uncommon, deep-seated soft tissue infection-> soft tissue gangrene
- Fournier’s gangrene-> scrotal/perineal form
- pre-existing immunodeficiency, diabetes
- subcut. strep infection with necrosis that is overtaken by anaerobes-> Gas formation on X-ray
- 50-70% mortality
subacute bacterial endocarditis
S. viridans, transient bacteremia following dental work
- left sided valvular endocarditis
- previously damaged heart valves at greater risk
- prophylactic antibiotics for dental work
puerperal sepsis
perinatal
-group B strep
what are pathological features with suppurative inflammation with cellulitis
diffuse interstitial neutrophilic infiltrates with minimal destruction of host tissue
- less likely to cause discreet abscesses like staph infections
- often deeper lesions which spread further than staph infections
- redness, pain, erythrogenic/pyrogenic toxins causes fever, rash
what are some ways to diagnose GABHS
rapid strep test-> has group A strep carbohydrate antigen
-confirmation culture 12-48 hours-> catalase negative, antibiotic specificity
rheumatic fever test: anti-streptolysin O Ab titers
impetigo is most common with
strep
why is necrotizing fasciitis common is those with diabetes?
lack of neutrophil function in diabetes because they are hyperglycemic, which is toxic to neutrophils
what do anti-streptolsyin O ab titers measure?
measure level of bodies response, not antibodies
