Microbiology

Question 1

List some clinical presentations of acute bone and joint infections

Answer 1

Temperature
Pain, redness, swelling
Reduced mobility

Question 2

Define SIRS (systemic inflammatory response syndrome)

Answer 2

2+ of
Temp less than 36 or more than 38
Heart rate more than 90
Resp rate more than 20
PaCO2 less than 4.3kPa
WBC more than 12k or less than 4k

Question 3

What is septic arthritis? How can it be introduced?

Answer 3

Infection of the joint space

Blood spread, direct innoculation or from infected bone

Question 4

What are the main organisms that cause septic arthritis?

Answer 4

Staph. aureus

Streptococci

Question 5

List diagnostic investigations for septic arthritis

Answer 5

Blood culture if pyrexial
Blood tests
Joint fluid aspirate for microscopy/culture
USS, XR, CT bone

Question 6

What is the main empirical treatment for septic arthritis?

Answer 6

Flucloxacillin (Staph. aureus)

N.B. high-dose IV to maximise uptake

Question 7

If there is a child under 5yrs old with septic arthritis, which antibiotic should be added and why?

Answer 7

Ceftriaxone for H. influenzae/Kingella cover

Question 8

How long does antibiotic treatment for septic arthritis usually last?

Answer 8

2-4 weeks

Question 9

What is osteomyelitis?

Answer 9

Inflammation of bone + their medullary cavity

Question 10

Which organisms cause chronic osteomyelitis?

Answer 10

Mycoplasma
Pseudomonas
Salmonella
Brucella (goat’s milk)

Question 11

Treatment and diagnosis of osteomyelitis is similar to septic arthritis. What is the key difference in terms of treatment length?

Answer 11

4-8 weeks duration of antibiotic treatment

Question 12

Which organisms cause type 1 necrotising fasciitis?

Answer 12

Mixed anaerobes and other bacteria

Question 13

Which organism causes type 2 necrotising fasciitis?

Answer 13

Group A Strep. (flesh-eating bacteria)

Question 14

List the mainstay treatment for necrotising fasciitis

Answer 14

Surgical debridement

Pencillin + clindamycin

Question 15

What is gas gangrene?

Answer 15

Spores forming in tissue, causing accumulation of gas bubbles

Question 16

What is tetanus?

Answer 16

Neurotoxin produced by Clostridium tetani prevents release of neurotransmitters, causing locked jaw/spastic paralysis

Question 17

When is vancomycin used empirically instead of flucloxacillin?

Answer 17

If MRSA, diptherioids, or penicillin-allergic

Question 18

Why is clindamicin useful?

Answer 18

Antitoxin properties - effective against PVL, group A Strep.

Question 19

Why do bacteria in biofilms pose a problem?

Answer 19

Resistant to immune system and antibiotics

Question 20

Why are superficial wound swabs a waste of time?

Answer 20

Reflect skin flora rather than deep infection (coag neg Staph. are part of flora)