Bone Infection

Question 1

What’s the clinical term for infection of the bone?

Answer 1

osteomyelitis

Question 2

What are the three ways of getting osteomyelitis

Answer 2

Haematogenous
Non-haematogenous direct (fracture/surgery)
Non-haematogenous through local invasion (ulcers)

Question 3

What’s the pathogenesis of bone infection

Answer 3

Usually, bacteria enters the looped capillaries for metaphysis. They get stuck at micro-capillaries near the sinusoids, forming abscess resistant to immune clearance. From there, it can spread to outer layer to cause periosteal lifting

Question 4

What are some factors causing the lack of clearance of bacteria in bone?

Answer 4

stuck in and block micro-capillaries
Abscess protected from immune system
pressure from pus limits blood supply

Question 5

What’s the most common causative agent for bone infection

Answer 5

Staph aureus

Question 6

Which strep species causes beta-haemolysis?

Answer 6

Strep pyogenes

Question 7

T/F Alpha-haemolysis is complete haemolysis with greening of the plate

Answer 7

False, beta-haemolysis is complete haemolysis, characterised by transparent clearing around the colony

Question 8

Which haemolysis is characterised by greening?

Answer 8

alpha!

Question 9

Which species can cause alpha-haemolysis?

Answer 9

Strep pneumoniae

Question 10

What are the commonest causative agents for osteomyelitis in newborn

Answer 10

Group B strep
Haemophilus influenzae
E Coli
Pseudomonas

Question 11

What are the commonest causative agents for osteomyelitis in post-surgery individual?

Answer 11

coagulase negative staphylococcus

Question 12

What are the commonest causative agents for osteomyelitis in post-chicken pox individual?

Answer 12

Strep pyogenes

Question 13

What are the commonest causative agents for osteomyelitis in an individual with penetrating foot injury?

Answer 13

pseudomonas

Question 14

What are the commonest causative agents for osteomyelitis in developing countries

Answer 14

TB

Haemophilus influenzae type B

Question 15

The route of bone infection can be different in adults vs. infants. How is that case?

Answer 15

infants have communicating vessels across growth plates, providing a passage for bacteria to invade into diaphysis + medullary cavity

Question 16

What are some general clinical presentations for osteomyelitis

Answer 16

pain, fever, warm, inflammation, swelling, limping in children

Question 17

What are the commonest bones for osteomyelitis

Answer 17

humerus, femur, tibia

long bones

Question 18

What are some differential diagnosis for osteomyelitis?

Answer 18

septic arthritis
malignancy
cellulitis

Question 19

T/F Blood culture is the most definitive diagnosis for osteomyelitis

Answer 19

False, by the time the person presents with symptoms, bacteria have mostly been cleared from blood

Question 20

What are the two inflammatory markers useful for diagnosing osteomyelitis? How do they differ in terms of timeframe

Answer 20

CRP and ESR
CRP goes up quickly in the first few hours and comes down in a few weeks

ESR rises much slower and goes down slowly as well

Question 21

Is X ray a good technique for diagnosing osteomyelitis?

Answer 21

Yes only if it’s late stage detection

Question 22

What’s the best test for osteomyelitis?

Answer 22

MRI

Question 23

What’s the treatment for gram +ve bacterial infection of bone

Answer 23

IV, high dose flucloxacillin

Question 24

Which generation of cephalosporin is best for

1) gram +ve bacteria
2) gram -ve bacteria

Answer 24

1) 1st gen

2) 3rd gen

Question 25

What’s the treatment for neonatal H. influenzae bone infection

Answer 25

flucloxacillin
cefotaxime
can add rifampicin for synergy

Question 26

How long should the treatment be for osteomyelitis

Answer 26

3-5 days IV antibiotics + 3 week course with oral antibiotics in uncomplicated cases