Bone Infection Flashcards
What’s the clinical term for infection of the bone?
osteomyelitis
What are the three ways of getting osteomyelitis
Haematogenous
Non-haematogenous direct (fracture/surgery)
Non-haematogenous through local invasion (ulcers)
What’s the pathogenesis of bone infection
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
What are some factors causing the lack of clearance of bacteria in bone?
stuck in and block micro-capillaries
Abscess protected from immune system
pressure from pus limits blood supply
What’s the most common causative agent for bone infection
Staph aureus
Which strep species causes beta-haemolysis?
Strep pyogenes
T/F Alpha-haemolysis is complete haemolysis with greening of the plate
False, beta-haemolysis is complete haemolysis, characterised by transparent clearing around the colony
Which haemolysis is characterised by greening?
alpha!
Which species can cause alpha-haemolysis?
Strep pneumoniae
What are the commonest causative agents for osteomyelitis in newborn
Group B strep
Haemophilus influenzae
E Coli
Pseudomonas
What are the commonest causative agents for osteomyelitis in post-surgery individual?
coagulase negative staphylococcus
What are the commonest causative agents for osteomyelitis in post-chicken pox individual?
Strep pyogenes
What are the commonest causative agents for osteomyelitis in an individual with penetrating foot injury?
pseudomonas
What are the commonest causative agents for osteomyelitis in developing countries
TB
Haemophilus influenzae type B
The route of bone infection can be different in adults vs. infants. How is that case?
infants have communicating vessels across growth plates, providing a passage for bacteria to invade into diaphysis + medullary cavity
What are some general clinical presentations for osteomyelitis
pain, fever, warm, inflammation, swelling, limping in children
What are the commonest bones for osteomyelitis
humerus, femur, tibia
long bones
What are some differential diagnosis for osteomyelitis?
septic arthritis
malignancy
cellulitis
T/F Blood culture is the most definitive diagnosis for osteomyelitis
False, by the time the person presents with symptoms, bacteria have mostly been cleared from blood
What are the two inflammatory markers useful for diagnosing osteomyelitis? How do they differ in terms of timeframe
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
Is X ray a good technique for diagnosing osteomyelitis?
Yes only if it’s late stage detection
What’s the best test for osteomyelitis?
MRI
What’s the treatment for gram +ve bacterial infection of bone
IV, high dose flucloxacillin
Which generation of cephalosporin is best for
1) gram +ve bacteria
2) gram -ve bacteria
1) 1st gen
2) 3rd gen
What’s the treatment for neonatal H. influenzae bone infection
flucloxacillin
cefotaxime
can add rifampicin for synergy
How long should the treatment be for osteomyelitis
3-5 days IV antibiotics + 3 week course with oral antibiotics in uncomplicated cases
