Streptococci

Question 1

what are some general characteristics of strep infections?

Answer 1

spreading of suppurative infections

-cellulitis, impetigo, erisypelas, GABHS

Question 2

what are some post-strep hypersensitivity disease?

Answer 2

• rheumatic fever

- immune complex glomerulonephritis

Question 3

Group A strep is associated with?

Answer 3

GABHS, beta hemolytic,

• S. pyogenes
• pharyngitis/post strep disease

Question 4

Group B strep is associated with?

Answer 4

peri-natal sepsis/newborn, UTI

Question 5

Viridans strep is associated with?

Answer 5

not one species

• alpha hemolytic,
• major cause of subacute bacterial endocarditis

Question 6

beta hemolytic strep

Answer 6

• clear, complete hemolysis

- Pyogenes: Group A, bactracin sensitive

Question 7

alpha hemolytic strep

Answer 7

green, partial hemolytic

• Pneumoniae
• Viridans

Question 8

Pneumoniae strep

Answer 8

optochin sensitive

• bile soluble
• capsule-> quellung

Question 9

Viridans strep

Answer 9

mutans, sanguis

• optochin resistant
• NOT bile soluble
• no capsule

Question 10

streptococcus mutans

Answer 10

major cause of dental caries

Question 11

gamma-hemolytic strep

Answer 11

Enterococcus
-E. faecalis
E. faecium

Question 12

what are the virulence factors of strep?

Answer 12

• cell wall polysaccharides
• capsules (M proteins)-> prevent phagocytosis
• enzymes: streptokinase, streptolysin O,S

Question 13

enzymes streptokinase, streptolysin O,S help strep to do what?

Answer 13

contribute ability to spread through tissues (cellulitis)

Question 14

what does strep erythrogenic toxin do?

Answer 14

skin rash

Question 15

what is the hosts response to strep?

Answer 15

antibodies to both capsular antigens and exotoxins

• M protein of many subtypes is antiphagocytic
• antibodies help in preventing recurrent pharyngeal infections in some

Question 16

antibodies to which strep can cross react to cause rheumatic fever?

Answer 16

Group A

• S. pyogenes
• deposition of immune complexes in kidney-> poststreptococcal glomerulonephritis

Question 17

What infections are associated with Group A strep?

Answer 17

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

Question 18

what are some post-streptococcal sequelae?

Answer 18

post-streptococcal glomerulonephritis:

rheumatic fever

Question 19

post-streptococcal glomerulonephritis

Answer 19

1-2 week after strep

• self-limited
• immune-complex mediated
• can see signs of acute renal failure->oliguria, hematuria, hypertension

Question 20

rheumatic fever

Answer 20

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

Question 21

strep infections: cellulitis, pyoderma

Answer 21

redness, swelling and pain

• less localized than staph infections
• abscesses are rare, and so are necrotizing fasciitis

Question 22

strep infections: impetigo

Answer 22

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

Question 23

strep infections: erysipelas

Answer 23

• groups A/C
• warm climates
• erythematous skin involvement without suppuration

Question 24

necrotizing fasciitis, “flesh eating disease”

Answer 24

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

Question 25

subacute bacterial endocarditis

Answer 25

S. viridans, transient bacteremia following dental work - left sided valvular endocarditis - previously damaged heart valves at greater risk - prophylactic antibiotics for dental work

Question 26

puerperal sepsis

Answer 26

perinatal | -group B strep

Question 27

what are pathological features with suppurative inflammation with cellulitis

Answer 27

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

Question 28

what are some ways to diagnose GABHS

Answer 28

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

Question 29

impetigo is most common with

Answer 29

strep

Question 30

why is necrotizing fasciitis common is those with diabetes?

Answer 30

lack of neutrophil function in diabetes because they are hyperglycemic, which is toxic to neutrophils

Question 31

what do anti-streptolsyin O ab titers measure?

Answer 31

measure level of bodies response, not antibodies