1. Understand basic pathophysiology of osteomyelitis and diabetic foot infections and how it impacts selection of antibiotics
and duration of treatment.
a. Three categories
i. Hematogenous Osteomyelitis
1. Spread thr
...
1. Understand basic pathophysiology of osteomyelitis and diabetic foot infections and how it impacts selection of antibiotics
and duration of treatment.
a. Three categories
i. Hematogenous Osteomyelitis
1. Spread through the blood
2. Vertebral osteomyelitis (adults)
ii. Osteomyelitis due to Contiguous Infection focus
1. Via a broken bone
2. posttraumatic/associated with broken bones
iii. Osteomyelitis associated with vascular insufficiency
1. Diabetic foot infections (increases pts risk of getting osteomyelitis)
b. Osteomyelitis Pathophysiology
i. Normal bone is highly resistant to infection and requires a predisposing factor
1. Very large amount of bacteria, trauma, and foreign bodies (prosthetics)
ii. Hematogenous osteomyelitis (20%) is often monomicrobial
iii. Osteomyelitis due to contiguous infection focus and diabetic foot are typically polymicrobial
iv. (1) Bacteria can express adhesins to promote binding and growth in bones
v. (2) Bacteria can adapt to the bone leading to persistence and high recurrence rate when treated for short
durations
vi. (3) Bacterial growth in bones causes pus formation and pressure buildup, which leads to bone necrosis
(sequestra) and then new bone formation
1. Acute osteomyelitis: no bone necrosis yet
2. Chronic osteomyelitis: bone necrosis (often >3 months since infection began) and requires surgery
c. Common Pathogens
i. S. aureus is the most common cause of osteomyelitis
ii. Everything else (<10%) → streptococcus species, gram negative bacilli, P. aeruginosa, anaerobes
d. Presentation/Diagnosis
i. Presentation → gradual onset over several days (or weeks in recurrent/chronic)
1. Pain, tenderness, warmth, erythema, and swelling
ii. Diagnosis
1. Local signs of inflammation (sometimes systemic)
2. Probe-to-bone test (useful for exclusion not really diagnosis)
3. Radiologic findings
4. Gold Standard = bone biopsy with bacterial growth and histologic findings of inflammation and
necrosis
iii. Osteomyelitis High risk factors
1. Bacteremia -- especially with healthcare
2. Compound fracture
3. Recent surgery
4. Chronic/poorly healing wounds -- ex: diabetic foot infections
e. Diabetic foot infection pathophysiology/presentation
i. Skin and soft tissue below the ankle -- with or without bone involvement
ii. 15-25% of patients with DM will develop a foot ulcer
iii. Patients with peripheral neuropathy, peripheral artery disease, and impaired immunity are at high risk →
inspect foot daily
iv. Not all diabetic foot ulcers are infected
v. Gram-positive cocci, especially staphylococci are the most common pathogen
2. Identify appropriate antimicrobial therapy and treatment duration for patients with osteomyelitis.
a. Empiric therapy is typically NOT necessary for osteomyelitis → wait for culture/sensitives whenever possible
b. If pt is hemodynamically unstable consider therapy that initially covers → MRSA, streptococci, gram negs
c. Therapy for Staphylococcus
i.
d. Therapy for Streptococcus
e. Therapy for Gram-Negatives
f. Special Considerations for Vertebral Osteomyelitis
i. Accounts for 5% of osteomyelitis cases and is caused by spread through the blood
ii. Patients usually present with acutely worsening back pain focused to one location with other general signs of
infection
iii. Most common pathogen: S. aureus (90% of cases)
iv. Risk factors → IVDA, hemodialysis, immunocompromised hosts
g. Special Considerations for Posttraumatic Osteomyelitis
i. Infections following open fractures
ii. Often come from skin, soil, hospital flora
iii. Recommend irrigation, debridement, and prophylaxis within 6 hours of open trauma to reduce osteomyelitis
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