Streptococcus

Question 1

GAS infection treatment

Answer 1

• penicillin

- clindamycin or linezolid for toxic shock syndrome

Question 2

Rheumatic fever treatment

Answer 2

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

Question 3

Post infectious/streptococcal GN

Answer 3

1-2 weeks after pharyngitis (high ASO)

4-6 weeks after pyoderma (low ASO)

Question 4

GAS prop

Answer 4

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

Question 5

GAS - pathogenesis

Answer 5

• 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

Question 6

GAS- virulent factors

Answer 6

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

Question 7

GAS- clinical presentations

Answer 7

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

Question 8

scarlet fever

Answer 8

• 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

Question 9

GAS- skin and soft tissue infection

Answer 9

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

Question 10

Streptococcal toxic shock syndrome

Answer 10

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

Question 11

Lab diagnosis of GAS

Answer 11

• 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

Question 12

Rheumatic fever

Answer 12

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

Question 13

Rheumatic fever- Jone’s criteria

Answer 13

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

Question 14

Rheumatic fever- prophylaxis

Answer 14

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

Question 15

post streptococcal GN

Answer 15

• 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

Question 16

Group B streptococcus- S. agalactiae: properties

Answer 16

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

Question 17

S. agalactiae- disease in infants

Answer 17

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

Question 18

S. agalactiae- disease in adult

Answer 18

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

Question 19

S. dysgalactiae- prop

Answer 19

• Group C/G
• PYR neg, VP neg
• bacitracin resistant

Question 20

S. dysgalactiae- disease

Answer 20

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

Question 21

S. anginosus- prop

Answer 21

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

Question 22

S. anginosus- disease

Answer 22

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

Question 23

Viridans streptococci - types

Answer 23

• oral flora

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

Question 24

Viridans streptococci- disease

Answer 24

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

Question 25

S. bovis

Answer 25

- 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

Question 26

Enterococci

Answer 26

- lancefield group D - high salt and temperature tolerance - PYR +ve - hydrolyse bile esculin associated disease: UTI endocarditis and bacteremia

Question 27

S. pneumoniae- prop

Answer 27

- not groupable by lancefield grouping - bile soluble - optochin sensitive - some serotypes have mucoid colonies and heavily encapsulated - diplococci

Question 28

S. pneumoniae- disease

Answer 28

- ENT (ear, nose throat): otitis media, sinusitis - pneumonia - meningitis - conjunctivitis - bacteraemia

Question 29

S. penumoniae- predispositions

Answer 29

- cochlea implants, chronic pulmonary disease | - acquired or congenital immunodeficiency

Question 30

S. pneumoniae- vaccines

Answer 30

- 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

Question 31

S. suis

Answer 31

- 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