Osteomyelitis Treatment

Factors to consider when choosing an antibiotic for empiric therapy

• Suspected pathogens & their antimicrobial susceptibility pattern
  • Empiric antibiotic coverage for S aureus is indicated

• Age of patient esp children
• Severity of infection
• History of recent antibiotic intake
• Current Gram stain results
• Underlying co-morbid conditions
• Antibiotic safety & efficacy

Antibiotics for Empiric Therapy

• Antibiotic treatment should be started after specimens for cultures are sent
  • However, treatment in an acutely ill patient should not be delayed to wait for bone debridement

• Empirical therapy of acute hematogenous osteomyelitis  in both children & adults should include coverage against S aureus
• IV antibiotics are given at the start of therapy; step-down to per orem treatment later may be possible based on clinical response

Antibacterial Combinations

• Eg Co-trimoxazole [Sulfamethoxazole (SMZ) & Trimethoprim (TM)]
• Effective against many Methicillin-resistant S aureus isolates but studies regarding effectiveness in osteomyelitis are limited
• TMP-SMZ is also active against streptococci & enterobacteriaceae

Beta-lactam Antibiotics

• Eg penicillins, cephalosporins, carbapenems
• Achieve therapeutic concentrations in bone
• 1st generation cephalosporins (eg Cefazolin) & Oxacillin are good initial choices for osteomyelitis suspected to be caused by methicillin-sensitive Staphylococcus aureus
  • Cefalexin & Cloxacillin are per orem agents that may be used to complete treatment

• Benzylpenicillin is the drug of choice for treating osteomyelitis caused by group A streptococcus, susceptible S pneumoniae & enterococci
  • Amoxicillin or Phenoxymethylpenicillin are per orem agents recommended for completing treatment

• Antipseudomonal penicillin, or Cefepime, or Ceftazidime &/or an aminoglycoside is an effective combination for osteomyelitis caused by Pseudomonas
• Ampicillin is effective against Salmonella
  • Cefotaxime or Ceftriaxone may be used for resistant isolates
• Most beta-lactam antibiotics are active against K kingae

Clindamycin

• Achieves good bone penetration
• May be used for empirical therapy of osteomyelitis suspected to be due to methicillin-sensitive Staphylococcus aureus & anaerobes
  • However, S aureus isolates susceptible to Clindamycin but resistant to Erythromycin should be tested for inducible macrolide-lincosamide-streptogramin B resistance through the D test
  • Treatment failure is more likely in the presence of inducible resistance
• Active against most isolates of S pyogenes & S pneumoniae

Linezolid

• May be as effective as Vancomycin in treating infections caused by Methicillin-resistant S aureus
• Active against streptococci & Vancomycin-resistant enterococci
• Alternative to prolonged IV therapy because of excellent oral bioavailability

Quinolones

• Eg Ciprofloxacin & Ofloxacin
• May be used for PO treatment of osteomyelitis in adults because of good penetration into the bone & excellent oral absorption
  • Not routinely recommended for use in young children

• May be used to treat osteomyelitis caused by gram-negative organisms including enterobacteriaceae
• Quinolones have variable coverage against S aureus & S epidermidis; no coverage against Enterococcus spp; newer quinolones have better action against Streptococcus spp & some anaerobes
• Should be combined w/ another antibiotic to achieve adequate coverage against S aureus during empiric therapy

Rifampicin

• May be used in combination w/ cell-wall antibiotics for synergistic action against S aureus
• Should never be used as monotherapy because resistance develops rapidly

Tetracyclines

• Effective against many Methicillin-resistant S aureus isolates but studies regarding effectiveness in osteomyelitis are limited
• Tetracycline use in young children may result in stunted bone & tooth growth; should only be considered in >8 yr of age
• Should be avoided in pregnant patients

Vancomycin

• Drug of choice for empiric therapy in areas where community acquired-Methicillin-resistant S aureus resistance to Methicillin & Clindamycin exceeds 10-15%
• Active against most isolates of S pyogenes, S pneumoniae & Ampicillin-resistant enterococci

• Antibiotic-impregnated (usually w/ aminoglycosides or Vancomycin) acrylic beads may be placed to sterilize a dead space while waiting for definitive management
• Limited studies are available to adequately support the superiority of local therapy over systemic antibiotic therapy, though local therapy is associated w/ markedly fewer adverse events

Suppressive Antibiotic Therapy

• Considered for patients in whom surgical treatment is needed but is not feasible
• Choose antibiotics that achieve adequate penetration into bone, have good bioavailability & low toxicity & are active against etiologic agents as based on sensitivity testing results
• Choices include Fusidic acid, quinolones, TMP-SMZ, Rifampicin (combined w/ other antibiotics)
• Treatment duration is usually 6 mth

Duration of Antibiotic Therapy

• Based on extent of infection, etiologic agent & clinical course
• Range is usually between 3-6 wk