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Block 2 > Streptococcus > Flashcards

Streptococcus Flashcards

1
Q

GAS infection treatment

A
  • penicillin

- clindamycin or linezolid for toxic shock syndrome

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2
Q

Rheumatic fever treatment

A

penicillin for 10 days,
anti-inflmmatory drugs for symptoms relieve e.g. corticosteroid, aspirin
surgery: uncontrolled heart failure secondary to acute MR

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3
Q

Post infectious/streptococcal GN

A

1-2 weeks after pharyngitis (high ASO)

4-6 weeks after pyoderma (low ASO)

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4
Q

GAS prop

A
  • S. pyogenes
  • bacitracin susceptible
  • PYR +ve, VP -ve
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5
Q

GAS - pathogenesis

A
  • directly caused by present of GAS: pharyngitis, skin and soft tissue infection, streptococcal toxin shock syndrome, scarlet fever
  • immunological reaction (non-suppurative complications): rhuematic fever, acute poststreptococcal glomerunephritis
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6
Q

GAS- virulent factors

A
  • adherence to epithelial cells/ anti-phagocytic: M proteins and capsule
  • spread and tissue invasion: streptokinase, hyaluronidase, protease
  • systemic toxicity: streptolysin O
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7
Q

GAS- clinical presentations

A
  • pharyngitis +/- scarlet fever
  • skin and soft tissue infection
  • streptococcal toxic shock syndrome
  • bacteremia
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8
Q

scarlet fever

A
  • day 2 rash (diffuse redish blue rash on upper chest that spread centrifugally, bleach on pressure)
  • strawberry tongue
  • Pastia’s line
  • facial flushing with perioral pallor
  • eosinophilia
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9
Q

GAS- skin and soft tissue infection

A

impetigo
cellulitis (rash with no distinct boundary), erysipelas (distinct boundary)
necrotising faciitis, myositis, myonecrosis

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10
Q

Streptococcal toxic shock syndrome

A

Lab diagnosis: isolation of GAS
Clinical presentation:
shock/ hypotension AND
multiorgan involvement (more than or equal to 2): renal involvement, liver involvement, coagulopathy, ARDS, skin and soft tissue infection, generalised erythematous macular rash with desquamation

caused by presence of superantigen which binds to non-specfic region of TCR

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11
Q

Lab diagnosis of GAS

A
  • culture of site of infection (skin or throat swab) or blood culture
  • antigen detection (rapid antigen detection test)
  • serology (antistreptolysin O titre) not for acute
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12
Q

Rheumatic fever

A

valvular damage caused by abnormal immune response to GAS infection
usually 3 weeks after GAS pharyngitis or skin infection
pathogenesis: molecular mimicry. Immune response directed against M proteins also attack cardiac proteins
Consequence: rheumatic heart disease

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13
Q

Rheumatic fever- Jone’s criteria

A

2 major or 1 major + 2 minor
Major: pan-carditis, arthritis, subcutaneous nodules, erythema marginatum, sydenham’s chorea
Minor: fever, arthralgia, prolonged PR interval, elevated CRP or ESP

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14
Q

Rheumatic fever- prophylaxis

A

Primary prophylaxis: same as treatment
Secondary prophylaxis: IM penicillin once every 21-28 days
5 years/till 18 if no carditis, resolved carditis 10 years or till 25, lifelong if moderate to severe rheumatic heart disease

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15
Q

post streptococcal GN

A
  • 1-2 weeks after pharyngitis with high ASO titre, 4-6 weeks after pyoderma with low ASO
  • may be caused by molecular mimicry, circulating immune complexes deposit or deposition of streptococcal Ag in glomerulus
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16
Q

Group B streptococcus- S. agalactiae: properties

A
  • bacitracin resistant
  • narrow zone beta hemolysis
  • CAMP test positive, hippurate hydrolysis positive
17
Q

S. agalactiae- disease in infants

A 
early onset (0-6): bacteraemia without a focus, meningitis, pneumonia
late onset (7-89): bacteraemia without a focus, meningitis, osteomyelitis, septic arthritis
Beyond early infancy: bacteraemia without a focus, less well-defined
18
Q

S. agalactiae- disease in adult

A

Pregnant women: UTI, infection in female genital tract, amnionitis, endometritis, post partum bacteraemia
Not pregnant: bacteraemia without a focus, pneumonia, meningitis, septic arthritis, osteomyelitis, skin and soft tissue, endocarditis
risk factor: elderly with co-morbidities

19
Q

S. dysgalactiae- prop

A
  • Group C/G
  • PYR neg, VP neg
  • bacitracin resistant
20
Q

S. dysgalactiae- disease

A

Group A + group B, but without rheumatic fever and Gn

21
Q

S. anginosus- prop

A
  • PYR -ve, VP +ve
  • bacitracin resistant
  • group A/C/F/G
  • maybe alpha or gamma hemolytic
  • characteristic caramel smell
22
Q

S. anginosus- disease

A
  • abscess formation (brain, liver, dental, lung/empyema)
  • endocarditis
  • bacteraemia in neutropenia cancer patients
23
Q

Viridans streptococci - types

A
  • oral flora

- S. anginosus, S. mitis, S. mutans, S. salivarius, S. sanguinis

24
Q

Viridans streptococci- disease

A
  • endocarditis
  • bacteremia in neutropenic patients (esp S. mitis)
  • dental caries
  • meningitis
  • pneumonia
25
Q

S. bovis

A
  • lancefield group D
  • Biotype 1 (S. gallolyticus): ferment mannitol, endocarditis, underlying colonic lesions
  • Biotype 2: more in HK, do not ferment mannitol, cholangitis, underlying hepatobiliary disease
26
Q

Enterococci

A
  • lancefield group D
  • high salt and temperature tolerance
  • PYR +ve
  • hydrolyse bile esculin

associated disease:
UTI
endocarditis and bacteremia

27
Q

S. pneumoniae- prop

A
  • not groupable by lancefield grouping
  • bile soluble
  • optochin sensitive
  • some serotypes have mucoid colonies and heavily encapsulated
  • diplococci
28
Q

S. pneumoniae- disease

A
  • ENT (ear, nose throat): otitis media, sinusitis
  • pneumonia
  • meningitis
  • conjunctivitis
  • bacteraemia
29
Q

S. penumoniae- predispositions

A
  • cochlea implants, chronic pulmonary disease

- acquired or congenital immunodeficiency

30
Q

S. pneumoniae- vaccines

A
  • pneumococcal polysaccharide vaccine and pneumococcal conjugate vaccine (better immunogenicity in children)
  • routine childhood immunization (2,4,6, 1y) or more than equal to 65
  • 2-64 with hx of invasive pneumococcal infection, immunocompromised, chronic disease or with cochlea implants
31
Q

S. suis

A
  • beta in horse blood, alpha in sheep blood
  • reservoir in pigs: butcher and meat preparer will be at risk
  • disease: meningitis, endocarditis, spondyloliscitis, bacteremia, arthritis

Block 2 (25 decks)

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