Micro - Class 5

What are the important diagnostic features of staphylococcus aureus?

1. Small yellowish colonies on blood

2. B-hemolysis

3. Coagulase positive

4. Ferments mannitol

Transmission of staphylococcus aureus?

Hands, sneezing, surgical wounds, contaminated food

S.aureus infections?

1. Skin infections

2. Deep localised infections

3. Abscesses in every internal organ

4. Bacteriaemia, sepsis

5. Hospital-acquired infections (HAIs)

6. Toxinoses

4 methods of staphylococcus aureus infection prevention?

1. To find carriers

2. Judicious use of antibiotics

3. Hygiene

4. Polyvalent vaccines

What is the antibiotic of choice for staphylococcus aureus carriers?

Mupirocin (intranasally)

What antibiotics is streptococcus pyogenes sensitive and resistant to?

Sensitive to bacitracin

Resistant to optochin

Transmission of streptococcus pyogenes?

Direct contact

Respiratory droplets

What does Hemolysin O and S do?

Hemolysin O: damages leukocytes, is highly immunogenic

Hemolysis S: lyses erythrocytes and leukocytes, not immunogenic

Function of spreading factors?

Streptokinase: conversion of plasminogen to plasmin, lysis of fibrin clot which allows bacteria to escape

Hyaluronidase: hydrolyses hyaluronic acid

Acute suppurative s.pyogenes infections:

1. Pharyngitis

2. Scarlet fever

3. Pyoderma-impetigo

4. Erisipelas

5. Necrotising fasciitis

Cause and signs of scarlet fever?

Caused by erythrogenic exotoxin

Signs:

1. Pastia’s lines - accentuation over skin folds with petechia

2. Desquamation of palms and soles (2 weeks later)

3. Strawberry tongue

What is pyoderma-impetigo?

Pyogenes skin infection with honey crusted lesions