Classification of Pathogenic Bacteria

Question 1

List clinically significant Gram positive bacteria and outline how they are identified or distinguished.

Answer 1

• Staphylococcus aureus (coagulase positive because it expresses the coagulase enzyme)
• This commensal organism is carried in nose, axilla and perineum (NAP)
• Can cause a wide range of diseases including: boils/abscesses (pus collection)
  septicaemia (blood poisoning)
  osteomyelitis (bone infection)

Question 2

State 2 types of Staphylococcus aureus

Answer 2

MRSA (very dangerous)

MSSA (easily treatable)

Question 3

State how staphylococcus aureus is penicillin resistant?

Answer 3

Produces penicillinase

Question 4

By different mechanisms, some staphylococcus aureus strains are also resistant to what?

Answer 4

Methicillin (this is a major problem for infection prevention and control in hospitals)

Question 5

State some coagulase negative staphylococci. (4)

Answer 5

S. lugdunensis
S. epidermidis
S. saprophyticus
S. haemolyticus

Question 6

Describe coagulase negative staphylococci.

Answer 6

Many different species, mainly skin commensals
Form biofilms and may be significant in the presence of foreign bodies/prostheses (such as prosthetic hip joints, heart valves and catheters)