Bone Infections Flashcards
What are the different categories of Osteomyelitis?
Hematogenous Direct Implantation Contiguous Infection of Prosthetic Device
Resulting from seeding of bone related to previous bacteremia
Hematogenous
Resulting from penetrating injury
Direct Implantation
Resulting from direct spread of bacteria from an overlying wound or pressure ulcer
Contiguous
Resulting from infection of prosthetic material implanted in bone, with spread of organism into the adjacent bone
Infection of Prosthetic Device
What type of osteomyelitis is most coming in children? Adults?
Children – Hematogenous Adults – Contiguous and Prosthetic
What is an example of contiguous osteomyelitis?
Diabetic foot ulcer
What types of pathogens cause hematogenous osteomyelitis?
Staphylococcus aureus
Streptococcus sp.
Gram negatives
Mycobacterium tuberculosis
Salmonella sp. (in sickle cell patients)
What type of pathogens cause direct implantation osteomyelitis?
Pseudomonas aeruginosa in nail injuries with sneakers
What type of pathogens cause contiguous osteomyelitis?
S. aureus
Gram negatives
Streptococcus sp.
Anaerobes
Candida sp.
What type of pathogens cause prosthetic joint infections?
Coagulase negative staphylococci
S. aureus
Gram-negatives
Streptococcus sp.
What are some general characteristics of osteomyelitis?
Often causes chronic infections that are difficult to eradicate.
Damge to periosteum may result in dead bone pieces (sequestrum) or new external bone formation (involucrum); localized abscesses may also occur (Brodie’s abscesses)
X-rays may be neg in early infections and are not very senstive to osteomyelitis; Bone/WBC scans or MRI imaging are more effective
Bacteria causing osteomyelitis can be obtained from bone biopsies or sometimes blood cultures.
What is most effective for diagnosing osteomyelitis?
Bone biopsy
What may be the result of damage to the periosteum in osteomyelitis?
Sequestrum (pieces of dead bone)
Involucrum (new external bone formation)
Localized abscesses (Brodie’s abscesses)
Does it work to get cultures of open ulcers overlying contiguous osteomeylitis?
No – they are notroiously unreliable.
The bacteria in the bone underneath may be entirely different.
What if bone biopsies can’t be done or cultures come back negative?
Empiric treatment will be needed
What is unique about prosthetic osteomyelitis?
Particularly difficult to treat
Often need to remove prosthesis
Biofilms may develop making infections even more difficult to treat
What are biofilms?
Aggregations of microorganisms adherent to a surface, particularly a hard surface like bones or teeth or prosthetic material
What is different between biofilm organisms and planktonic (suspended) organisms?
The biochemistry and physiology
Biofilm bacteria are likely to be more resistant to antibiotics than are planktonic bacteria
What is the treatment for osteomyelitis?
Long course antibiotics
Generally 6 wks of intravenous therapy
Surgery may be needed to remove sequestra or prostheses
Which antibiotic is useful in treating biofilm organisms?
Rifampin
When is antibiotic treatment only useful?
When bone is covered by tissue – otherwise new organisms can continuously invade the bone
