Lecture 25 - Bone and Joint Infections Part 1

what are the 3 main types of bone and joint infections

Osteomyelitis

Prosthetic Joint Infection

Septic Arthritis

what is osteomyelitis

Infection of the bone

May be acute or chronic

Up to 24% of patients with diabetic foot ulcers

Progressive destruction of the bone and the formation of sequestra

what are the mechanisms of infection in osteomyelitis

Hematogenous seeding → More common in children

Contiguous spread from adjacent soft tissues and joints

Direct inoculation of microorganisms into bone as a result of trauma or surgery

Once established, the pathogens produce local inflammation that produces bone necrosis and formation of sequestra

what are risk factors for osteomyelitis

Circulatory disorders → Diabetes, Peripheral vascular disease

Open fracture or surgery

Chronic soft tissue infection

Immunocompromise

IV drug or catheter use

Pressure ulcers

what is the clinical presentation of acute osteomyelitis

Typically within 2 weeks of initial infection

More common in children

Systemic symptoms

Local signs/symptoms

what are systemic symptoms of acute osteomyelitis

Fever

Lethargy

Irritability

what are local s/s of acute osteomyelitis

Acute onset pain/tenderness at affected site

Erythema, swelling

Delayed wound healing

what is the clinical presentation of chronic osteomyelitis

Months or years after initial infection

More common in adults

Signs/symptoms

In patients with generalized vascular insufficiency (e.g., diabetes)

• Perforating foot ulcer may be present

• May be painless (if peripheral neuropathy)

what are s/s of chronic osteomyelitis

Low grade fever

Chronic pain

Delayed wound healing

Persistent sinus tract or wound drainage

Soft tissue damage

Exposed bone

Bone instability

what investigations are done for osteomyelitis

Blood cultures (if febrile)

Bone cultures

CBC/diff

SCr

ESR or CRP (inflammation)

what imaging should be done in osteomyelitis

Plain x-ray ± MRI, or

Bone scan ± WBC scan

how is osteomyelitis diagnosed

Diagnosis of OM usually first suspected based on clinical findings and confirmed with a combination of radiologic, microbiologic, and pathologic tests

what are the most common pathogens in osteomyelitis

> 50% of cases:

• Staphylococcus aureus

  • MRSA may account for more than 1/3 of staphylococcal isolates in adults

• Coagulase-negative staphylococci - S. lugdunensis

what are other less common pathogens in osteomyelitis

< 25% of cases:

• Streptococcus spp, Enterococcus spp, Enterobacterales, Pseudomonas spp, Anaerobes, Mycobacterium tuberculosis

Rarely (< 5% of cases):

• Mycobacterium avium complex, Mycoplasma spp, Fungi, Brucella spp, Salmonella spp

what are the general principles of osteomyelitis management

combination of antibacterial and surgical therapy

Wherever possible, antimicrobial therapy should be withheld until percutaneous aspirate or deep surgical cultures have been obtained

Duration of therapy often depends on results of surgical interventions

what is an exception where antimicrobial therapy can be started before aspirate or cultures are obtained

concomitant soft tissue infection or sepsis syndrome

what is the duration of ABX if margins not clear following debridement

4-6 weeks of parenteral antibacterial generally required

what is the duration of ABX if amputation and clear margins at surgery

shorter course (2-5 days) can be given

what duration of ABX for patients not suitable for surgery

consider long-term suppressive therapy (6 months to lifelong)

what are the usual pathogens in hematogenous, long bones osteomyelitis

MSSA/MRSA

Rare: Streptococcus spp Enterobacterales M. tuberculosis Fungi

how long should IV treatment be used in hematogenous, long bones osteomyelitis

Recommended minimum 2 weeks with IV, then switch to PO agents with good bioavailability and bone penetration may be considered with clinical improvement

what is empiric management of hematogenous, long bones osteomyelitis

cloxacillin IV or cefazolin

4-6 weeks (minimum 8 weeks if MRSA)

what is empiric management of hematogenous, long bones osteomyelitis if penicillin/cefazolin allergy or MRSA suspected

vancomycin IV

4-6 weeks (minimum 8 weeks if MRSA)

when should MRSA coverage be considered

Preceding trauma, multifocal lesions, or disease in adjacent muscle

what are the usual pathogens in contiguous, vascular insufficiency, diabetic foot osteomyelitis

MSSA/MRSA

Streptococcus spp

Enterococcus spp

Enterobacterales

P. aeruginosa

Anaerobes

Candida spp

(Often polymicrobial)

how long should IV treatment be used in contiguous, vascular insufficiency, diabetic foot osteomyelitis

Switch to PO therapy should be guided by clinical improvement and deep tissue C&S results

what is empiric therapy for mild-moderate contiguous, vascular insufficiency, diabetic foot osteomyelitis

Amoxi/clav PO or

[cefazolin IV ± metronidazole PO]

what is empiric therapy for mild-moderate contiguous, vascular insufficiency, diabetic foot osteomyelitis if MRSA is suspected

Amoxi/clav PO or [cefazolin IV ± metronidazole PO]

PLUS [TMP/SMX PO or doxycycline PO]

when should you consider MRSA coverage for contiguous, vascular insufficiency, diabetic foot osteomyelitis

Previous (prior 12 months) or current MRSA infection/colonization, recent antibacterial use, or recent hospitalization

when is anaerobic coverage recommended for contiguous, vascular insufficiency, diabetic foot osteomyelitis

Severe ischemia, foul-smelling discharge, necrosis, or gangrene

what is empiric treatment for moderate-severe contiguous, vascular insufficiency, diabetic foot osteomyelitis

[vancomycin + ceftriaxone + metronidazole[

or Amoxi/clav