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Microbiology-1 > Strep > Flashcards

Strep Flashcards

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

25
erysipelas
26
cellulitis
s. pyogenes most common cause
27
necrotizing fasciitis
28
scarlet fever
erythrogenic toxin mediate disease diffuse sandpaper rash
29
s. pyogenes sequelae
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
What is the presentaion of acute glomerulonephritis?
- 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
acute rheumatic fever presentation
- 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
How to prevent acute rheumatic fever?
- 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
Strep pyogenes treatment
all group A are sensitive to penicillin G -treat strep pharyngitis w/ antibiotics for reducing symp and prevent RF
34
What is the virulence factor in strep Pneumonia?
polysacc capsule- antiphagocytic
35
Antibodies of Strep Pneu
\>90 diff capsular types (very specific) promote phagocytosis ab from natural infect or immunization Quellung rxn: anticapsular ab causes capsule to swell
36
Where is strep pneu located
normal flora of oropharyn most common cause of community acquired pneumonia also cause bacteremia and bact meningitis, upper resp infections (otitis media, sinusitus)
37
What are the clinical features of strepto pneumoniea?
high fever, chills, cough, dyspnea, pleuritic chest pain purulent sputum: "rust colored" bacteremia in 10-20% cases
38
What people are at higher risk for invasive pneumococcal disease?
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
How do you diagnose strep penumoniae?
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
S. Pneumoniae treatment
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
What are two vaccines for S. Pneumoniae?
1. polysaccharide vaccine (adults/older children) 23 valent (for high risk adults including \>65yo, 19-64yr immmunosup ppl) 2. 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
What are two main enterococcus antigens?
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
VRE is common cause of nosocomial infections
- mostly in sick/immunocomp ppl - bacteremia, UTI, wound infect - mostly E. faecium - positive VRE culture rep colonization, not necessarily infectoin
44
Mechanism of VRE:
altered cell wall oligopeptide (impt for peptido syn) with low binding affinity for vanco -\>decreased inhibition of peptidoglycan synthesis
45
where are VRW usually acuired?
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
Treatment for Enterococcus
1. if penicillin sensitive: penicillin + aminoglycoside for synergy 2. peniillin resistance: vanco 3. VRE resistance: linezolid or daptomycin
47
Strep bovis
group D. NOT grown in NaCl association with bacteremia and endocarditis w/ colon carcinoma
48
what are some types of Viridans streptococus?
s. mitis, s. sanguis, s. mutans (dental caries) normal flora of oropharynx
49
How does viridans present?
common cause of infective endocarditis - endo several wks after dental procedure - fever, heart murmur, anemia, embolic events
50
Streptococus agalactiae
group B genital tract of some woemn causes neonatal meningitis and sepsis, and postpartum endometritis
51
Streptococus agalactiae: prevention
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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