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Microbiology-1 > Strep > Flashcards

Strep Flashcards

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1
Q

strep pyrogenes

A

pharyngitis and skin/soft tissue infections

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2
Q

viridans strept

A

infective endocarditis

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3
Q

strep pneumoniae

A

pneumonia, upper rest tract infect & meningitis

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4
Q

enterococcus faecalis & enterococcus faecium

A

nosocomial infections

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5
Q

distinguishing test between staph and strep

A

catalase test

strep is negative

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6
Q

strep gran stain and culture

A

gram + cocci

spherical

chains or pairs

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7
Q

which bacteria is Beta hemolytic?

A

streptococcus pyogenes

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8
Q

streptococcus pneumonia: hemolysis, solubility in bile, optochin resistance?

A

alpha

bile soluble

inhibited by optochin

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9
Q

viridans strep

A

“green strep”

alpha

not bile soluble

not inhibited by optochin

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10
Q

Group A:

A

strepto pyrogens (sensitive to bacitracin)

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11
Q

Group B:

A

streptococcus agalactiae (resistant to bacitracin, hydrolyzes hippurate)

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12
Q

Group D:

A

hydrolyzes esculin in presence of bile- produces black pigment

  1. enterococcus: grows in nacl
  2. strep bovis: no growth in nacl
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13
Q

What is the most important virulance factors in strep pyogens?

A
  1. M protein: inhibits opsonization: block phago

antibody M strain specific immunity

  1. capsule: antiphagocytic

antibodies not made against capsule bc made of HA (found in body)

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14
Q

Strep enzymes:

A

streptokinase: activates plasminogen to form plasmin (dissolves fibrin clots)

streptolysin O: anti (ASO) AB used as marker of recent group A strep infection

* high ASO useful for dignosing rheumatic fever

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15
Q

Strep toxins:

A

erythrogenic toxin: causes rash of scarlet fever

-superantigen ( T cell divide and produce cytokines)

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16
Q

Toxins involved in clinical presentation of Strep pyogenes.

A

Toxic shock syndrome: exotoxin A (superantigen)

*similar to staph (but strep has site of soft tissue infectoin & +culture)

necrotizing fascitis- exotoxin B

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17
Q

where is streptococcus pyogenes normally found

A

skin, oropharynx

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18
Q

What are the three types of diseases it causes?

A
  1. pyogenic
  2. toxigenic
  3. immunilogic
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19
Q

explain the pyogenic (Strep pyrogenes) disease

A

inflammatio induced locally at site whre orgasm are present

  1. pharyngitis
  2. cellulitis
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20
Q

explain the toxigenic (Strep pyrogenes) disease

A

exotoxin production can cause systemic symptoms at sites where not organism is found

  1. scarlet fever
  2. toxic shock syndrome
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21
Q

explain the immunologic (Strep pyrogenes) disease

A

causes inflammation at site where no ogms (sequelae)

  1. rheumatic fever
  2. acture glomerulonephritis
22
Q

Strep throat

A

strep pyogenes

pharyngitis

main disease in children and adolescents

fever, sore throat w/ tonsillopharyngeal erythemia and exudates, tender cerival LN

elevated WBC

23
Q

strep throat detection test and treatment

A
  1. throat swab for antigen detection test or culture
    - distinguish infect vs normal flora
  2. usually recover spontaneously
    - may prevent rheumatic fever
  3. can extennd to cause pharyngeal abscess, otitis, sinusitis, mastoiditis, meningitis
24
Q

strep pyogenes: skin and soft tissue infections

A
25
Q

erysipelas

A
26
Q

cellulitis

A

s. pyogenes most common cause

27
Q

necrotizing fasciitis

A
28
Q

scarlet fever

A

erythrogenic toxin mediate disease

diffuse sandpaper rash

29
Q

s. pyogenes sequelae

A
  1. acute glomerulonephritis
    - immune complex deposits in glomerular BM
  2. Acute rheumatic fever
    - autoimmune disease: ab to strep B protein cross react w/ human antigens in join, heart, brain
30
Q

What is the presentaion of acute glomerulonephritis?

A
  • mainly in children
  • after skin/soft tissue infection or pharyngitis
  • HTN, Edema of face/ankles, hematuria (smoky or rust colored urine), proteinuria
  • elevated ASO titier
  • most recover completely
  • no prevention
31
Q

acute rheumatic fever presentation

A
  • mainly in children and adolescents
  • occurs after pharyngitis (NOT skin/soft tissue infect)
  • fever, migratory polyarthritis, rash, carditis (mitra and aortic valve damage)
  • elevated ASO titers
32
Q

How to prevent acute rheumatic fever?

A
  • treating strep pharyngitis within 9 days of onset w/ antibiotics
  • reinfection causes exacerbation: prevent w/ long-term antibiotic prophylaxis
  • ab prohylaxis prior to invasive dental procedure (prevent infective endocarditis)
33
Q

Strep pyogenes treatment

A

all group A are sensitive to penicillin G

-treat strep pharyngitis w/ antibiotics for reducing symp and prevent RF

34
Q

What is the virulence factor in strep Pneumonia?

A

polysacc capsule- antiphagocytic

35
Q

Antibodies of Strep Pneu

A

>90 diff capsular types (very specific)

promote phagocytosis

ab from natural infect or immunization

Quellung rxn: anticapsular ab causes capsule to swell

36
Q

Where is strep pneu located

A

normal flora of oropharyn

most common cause of community acquired pneumonia

also cause bacteremia and bact meningitis, upper resp infections (otitis media, sinusitus)

37
Q

What are the clinical features of strepto pneumoniea?

A

high fever, chills, cough, dyspnea, pleuritic chest pain

purulent sputum: “rust colored”

bacteremia in 10-20% cases

38
Q

What people are at higher risk for invasive pneumococcal disease?

A

newborn

elderly

alcohol or drug intox (depressed cough reflex; aspiration of secretions)

immmunodeficiency/ AIDS

SS anemia (functional hyposplenism)

-splenectomy/hyposplenism increases chance of severe disease w/ overwhelming pneumococcal sepsis.

39
Q

How do you diagnose strep penumoniae?

A

gram stain (sputum, CSF)

latex agglutination test of CSF is a rapid test

urinary antigen test (detects C-polysac from cell wall/good for bacteremia infect)

40
Q

S. Pneumoniae treatment

A
  1. Mechanism: altered penicilin binding protein (imporant for synthesis of peptidoglycan in bacterial cell wall) w/ decreased binding affinity for penicillin
    - not inhibited by b-lactamase inhibitor
  2. S. pneumoniae penicillin resistance is dose-dependent.

(can use higher doses of penicillin for strains w/ reduce susecptibility )(except meningitis)

41
Q

What are two vaccines for S. Pneumoniae?

A
  1. polysaccharide vaccine (adults/older children)

23 valent (for high risk adults including >65yo, 19-64yr immmunosup ppl)

  1. conjugate vaccine (young children)

polysaccaride conjugated to a carrier protein (diphtheria toxoid)–>stimulates Helper T cell response that enahnces b cell ab production.

13 valent

42
Q

What are two main enterococcus antigens?

A

group D, grow in NACL

  1. E. faecalis: usually not resistant to vanco
  2. E. faecium: less common, more likely to be resistant to vanco
43
Q

VRE is common cause of nosocomial infections

A
  • mostly in sick/immunocomp ppl
  • bacteremia, UTI, wound infect
  • mostly E. faecium
  • positive VRE culture rep colonization, not necessarily infectoin
44
Q

Mechanism of VRE:

A

altered cell wall oligopeptide (impt for peptido syn) with low binding affinity for vanco

->decreased inhibition of peptidoglycan synthesis

45
Q

where are VRW usually acuired?

A

hospital

shed VRE in stools which contaminates skin and evnir.

transmitted by healthcare workers

patietns require contact isolation (wear gloves and gown, no mask)

46
Q

Treatment for Enterococcus

A
  1. if penicillin sensitive: penicillin + aminoglycoside for synergy
  2. peniillin resistance: vanco
  3. VRE resistance: linezolid or daptomycin
47
Q

Strep bovis

A

group D. NOT grown in NaCl

association with bacteremia and endocarditis w/ colon carcinoma

48
Q

what are some types of Viridans streptococus?

A

s. mitis, s. sanguis, s. mutans (dental caries)

normal flora of oropharynx

49
Q

How does viridans present?

A

common cause of infective endocarditis

  • endo several wks after dental procedure
  • fever, heart murmur, anemia, embolic events
50
Q

Streptococus agalactiae

A

group B

genital tract of some woemn

causes neonatal meningitis and sepsis, and postpartum endometritis

51
Q

Streptococus agalactiae: prevention

A

screen w/ vaginal and rectal cultures 35-37wks preg

rapid antigen test

if +, treat with penicillin G at time fo delivery

Microbiology-1 (8 decks)

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