Medical Microbiology

Question 1

List two organisms that are most likely to be associated with prosthetic joint infections.

Answer 1

NB!! Most common are Coagulase negative Staphylococci e.g., S.epidermidis and S.capitis
as well as S.aureus
Beta haemolytic Streptococci (S.pyogenes)

Question 2

8. Define the term “biofilm” and explain why it is possible that it could be present in this case?

Answer 2

A biofilm is a group of organisms that stick together in a matrix to evade the immune
system(1/2), this is often associated with foreign material (½). This patient has a prosthetic
joint

Question 3

Briefly outline what is meant by the terms A: “septic arthritis” and B: “osteomyelitis

Answer 3

A: infection of the joint
B: Inflammation/infection of bone

Question 4

. Outline the management of any apyrexial patient with a diagnosis of
“abscess/carbuncle without surrounding cellulitis”.

Answer 4

Incision and drainage only, no antibiotics required.

Question 5

Outline the management of Michael’s case, assuming that he has cellulitis.

Answer 5

Antibiotics such as cloxacillin are indicated.

Question 6

State what is important to consider when a coagulase negative Staphylococcus is
isolated from a superficial skin swab.

Answer 6

It is a foreign body organism which has been retrieved throgh extrogenous infection, whether directly or indirectly.

Question 7

Define the term “MRSA” and what extra precautions must be taken to prevent its
spread.

Answer 7

“Methicillin resistant Staphylococcus aureus” , this requires contact precautions like
hand hygiene, gloves, gowns to prevent spread of the organism to other
patients/staff members.