20 - Bone Infections Flashcards
What are the four categories of osteomyelitis? Describe each.
- Hematogenous: resulting from seeding of bone related to a previous bacteremia
- Direct Implantation: resulting from penetrating injury
- Contiguous: resulting from direct spread of basteric from an overlying wound or pressure ulcer
- Infection of Prosthetic Device: from infection of prosthetic material implanted in bone, with spread into adjacent bone.
Which type of osteomyelitis tends to be more common in children and is usually monomicrobial?
Hematogenous osteomyelitis
Which type of osteomyelitis tends to be more common in adults and is usually polymicrobial?
Contiguous osteomyelitis.
What organisms usually cause hematogenous osteomyelitis?
Staph. aureus, strep. sp., gram negatives, mycobacterium tuberculosis, and salmonella sp in sickle cell pts.
What organisms usually cause direct implantation osteomyelitis?
Pseudomonas aeruginosa - common in nail injuries with sneakers
Other organisms can be implanted too.
What organisms usually cause contiguous osteomyelitis?
S. aureas, gram-negatives, strep. sp., anaerobes, and candida sp.
What organisms usually cause prosthetic joint infection osteomyelitis?
Coagulase negative staphylocicci, S. aurea, gram negatives, strep. sp., and probionibacterium acnes.
What organism accounts for 70-90% of hematogenous osteomyelitis cases in children?
Staphylococcus aureas.
What organisms are more frequent in patients with UTIs or infections from IV drug use?
Gram negatives such as E. coli, pseudomonas, klebsiella, enterobacter.
How common is it for pts with TB to have bone infections? How do these occur?
1-3% will have a bone infection with TB.
These can be through the bloodstream or from direct extension from a pulmonary focus (to ribs or vertebral bodies).
What STD can infect bone?
Syphilis, in chronic or congenital cases.
What has become an important pathogen in shoulder replacement infections?
Propionibacterium acnes.
What are can osteomyelitis cause?
Chronic infections that are difficult to eradicate.
Fever (most common in acute, but rare in chronic)
Damage to periosteum may result in pieces of dead bone (sequestration) or new external bone formation (involucrum).
Localized abcesses may occur (Brodie’s abscesses).
How would you diagnose osteomyelitis? How would you identify the bacteria?
X rays may be negative early in infections and are not very sensitive.
Bone/WBC scans or MRI imaging is more effective.
Bacteria can be obtained from bone biopsies or sometimes blood cultures.
What is notoriously unreliable in determining the tyep of bacteria causing the bone infection? Why is this?
Cultures of open ulcers overlying contiguous osteomyelitis because the bacteria in the bone underneath may be entirely different.