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Microbiology (bacteria) > streptococcus > Flashcards

streptococcus Flashcards

1
Q

process of identify strep

A

1) hemolysis
2) if beta-hemolysis, test for carbohydrate A-O with exception of D
3) if A, check M protein 1-90

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2
Q

strep group A known as:

A

S. pyogenes

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3
Q

appearance of gamma hemolysis

A

nothing

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4
Q

appearance of alpha hemolysis

A
  • cloudy green due to remaining intact RBCs with altered green heme pigment
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5
Q

appearance of beta hemolysis

A
  • clear, fully lysis of RBCs
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6
Q

S. pyogenes, where found?

A

skin, oropharynx

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7
Q

S. pyogenes extracellular proteins for bacterial proliferation

A
  • streptolysins - lyse red cells, cause beta-hemolysis, O is oxygen labile, antigenic, leads to ASO antibody titers important in lab diagnosis, S is poorly antigenic and oxygen stable
  • streptokinase - proteolysis, destroys fibrin clots
  • DNAase
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8
Q

S. pyogenes antiphagocytic elements

A
  • hyaluronic acid capsule

- M-proteins, strains with large amount of M-protein are more resistant to phagocytosis

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9
Q

what does Spe stand for?

A

streptococcal pyrogenic extoxin

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10
Q

what is caused by SpeA, B, and/or C?

A
  • rash of scarlet fever

- strep toxic shock syndrome

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11
Q

what are the S. pyogenes toxin-mediated diseases?

A
  • scarlet fever

- strep toxic shock syndrome

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12
Q

characteristics of strep toxic shock syndrome

A
  • severe hypotension
  • two or more of following: impaired renal function, DIC, impaired liver function, resp distress, rash, soft tissue necrosis
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13
Q

S. pyogenes invasive syndromes

A
  • puerperal fever - uncommon in developed countries, infection of uterus immediately after childbirth
  • acute pharyngitis/tonsilitis (strep throat)
  • impetigo - mild child superficial skin infection
  • erysipelas - severe cellulitis of dermis and underlying tissue
  • necrotizing fasciitis - flesh-eating bacteria disease
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14
Q

what is a good test to narrow strep down to group A?

A

if it is sensitive to bacitracin, other groups are resistant

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15
Q

2 sequelae of S. pyogenes

A
  • rheumatic fever - 2-3 weeks after sore throat, antibodies react with antigens on heart etc.
  • acute glomerulonephritis - immune complexes deposit that contain bacterial antigens
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16
Q

test for recent S. pyogenes infection

A
  • titer of 160 or greater for antibody to streptolysin O or four-fold increase in ASO titer
17
Q

S. pyogenes treatment

A

PENICILLIN - no resistance to penicillin recorded

18
Q

most important species of group B strep

A

S. agalactiae

19
Q

S. agalactiae, where found?

A

vagina, colon

20
Q

major disease from S. agalactiae

A

1/3 of neonatal infections - septicemia, meningitis, pneumonia, death

21
Q

two epidemiological patterns of S. agalactiae

A
  • early onset - vaginal during birth, penicillin or ampicillin
  • late onset - infant to infant spread within nursery
22
Q

group D strep are known as:

A

enterococci

23
Q

entercocci, where found?

A

common inhabitants of GI tract

24
Q

common diseases from enterococci

A

UTI, wound infections, sepsis

25
Q

enterococci treatment

A
  • resistant to many antibiotics

- vancomycin is last resort

26
Q

most important enterococci species

A
  • E. faecalis

- E. faecium

27
Q

viridans streptococci hemolysis?

A

alpha hemolysis

28
Q

most common viridans streptococci species:

A
  • S. mutans

- S. sanguis

29
Q

viridans streptococci, where found?

A

mouth, nose, pharynx

30
Q

diseases caused by viridans streptococci

A
  • frequent cause of INFECTIVE ENDOCARDITIS, often fatal when untreated
31
Q

streptococcus pneumoniae known as:

A

pneumococcus

32
Q

pneumococcus gram stain and shape

A

diplococci, lancet shaped, gram positive

33
Q

pneumococcus pathogenesis

A
  • pneumococcal capsule hinders phagocytosis
  • IgA protease degrades surface IgA on respiratory epithelium
  • pneumolysin, lytic enzyme contributes to pathogenesis
34
Q

pneumococcus disease

A
  • most frequent cause of bacterial pneumonia (cough, fever, chills, lung pain, rusty sputum, leukocytosis,
  • meningitis
  • otitis
35
Q

who are at high risk for pneumococcal pneumonia?

A
  • immunocompromised
  • splenectomy
  • sickle cell anemia

Microbiology (bacteria) (16 decks)

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