Microbiology Flashcards
Staphylococcus
Gram positive cocci in clusters
Aerobic and facultative anaerobes.
Name the two important types of staphylococcus
Staph aureus
Coagulase negative staph
What differs staph aureus from other staphylococci?
On coagulase testing- staph aureus stains golden (only one that is coagulase +ve) whereas coagulase negative staph stay white.
Staph aureus
Common human pathogen
Produces enzymes (including coagulase)
Causes wound, bone, skin and joint infections
Some strains produce toxins
Give examples of toxins produced by staph aureus
Enterotoxin- food poisoning
SSSST- staph scalded skin syndrome toxin
PVL- panton Valentine leukocidin
Coagulase negative staph
Skin commensals
May cause infection in association with implanted artificial material e.g. heart valves.
Staph saprophyticus
Causes urinary tract infections.
Streptococcus
Gram positive cocci in chains
Aerobic and facultative anaerobes.
How are streptococci classified?
Haemolysis
Alpha haemolysis- partial heamolysis- kind of green looking
Beta haemolysis- complete haemolysis- obvious yellowy white
Gamma haemolysis- no change (no haemolysis)
Beta haemolytic streptococci
Pathogenic organisms
What toxin is produced by beta haemolytic streptococci?
Haemolysin- one of the many toxins produced. Can damage tissues.
How are beta haemolytic streptococci further classified?
Antigenic structure on surface (serological grouping)
Group A beta haemolytic strep cause which types of infections.
Throat, severe skin infections
Group B beta haemolytic strep cause which types of infections
Meningitis in neonates.
Alpha haemolytic streptococci
There are 2 important catergories- strep pneumoniae (commonest cause of pneumonia) and strep viridans (commensal of mouth, throat and vagina)
