What empiric antibiotics and treatment duration are recommended for a prosthetic joint infection following hip replacement in an older adult?

Antibiotic Choice in Post Hip Replacement Infection

Empiric Therapy

Empiric antibiotics for prosthetic joint infection following hip replacement should include vancomycin 15 mg/kg IV every 12 hours PLUS an anti-gram-negative agent (cefepime 2 g IV every 12 hours or meropenem 1 g IV every 8 hours) until culture results are available. 1

• This broad-spectrum approach covers the most common pathogens: methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible Staphylococcus aureus (MSSA), coagulase-negative staphylococci, and gram-negative organisms including Pseudomonas aeruginosa. 1
• Staphylococci account for >50% of prosthetic joint infections, making anti-staphylococcal coverage essential. 2
• Obtain 3-6 intraoperative tissue samples before initiating antibiotics whenever possible to maximize diagnostic yield and guide definitive therapy. 3

Pathogen-Specific Definitive Therapy

Once culture results are available, narrow therapy based on the identified organism:

Staphylococci (Oxacillin-Susceptible)

• Preferred: Nafcillin 1.5-2 g IV every 4-6 hours OR cefazolin 1-2 g IV every 8 hours OR ceftriaxone 1-2 g IV every 24 hours 1, 3
• Alternatives: Vancomycin 15 mg/kg IV every 12 hours, daptomycin 6 mg/kg IV every 24 hours, or linezolid 600 mg PO/IV every 12 hours 1
• Add rifampin 300-450 mg PO twice daily (or 600 mg once daily) if debridement with implant retention or one-stage exchange is performed, but only after wounds are dry to prevent resistant organism superinfection. 1

Staphylococci (Oxacillin-Resistant/MRSA)

• Preferred: Vancomycin 15 mg/kg IV every 12 hours 1
• Alternatives: Daptomycin 6 mg/kg IV every 24 hours or linezolid 600 mg PO/IV every 12 hours 1
• Add rifampin as above for retained implants 1
• Target vancomycin trough of 15-20 mcg/mL for MRSA infections without rifampin or local vancomycin spacer; trough ≥10 mcg/mL may be adequate when rifampin or vancomycin-impregnated spacers are used. 1

Enterococcus (Penicillin-Susceptible)

• Preferred: Penicillin G 20-24 million units IV every 24 hours continuously or in 6 divided doses OR ampicillin 12 g IV every 24 hours continuously or in 6 divided doses 1
• Alternatives (penicillin allergy only): Vancomycin 15 mg/kg IV every 12 hours, daptomycin 6 mg/kg IV every 24 hours, or linezolid 600 mg PO/IV every 12 hours 1
• Aminoglycoside addition is optional 1

Pseudomonas aeruginosa

• Preferred: Cefepime 2 g IV every 12 hours OR meropenem 1 g IV every 8 hours 1
• Alternatives: Ciprofloxacin 750 mg PO twice daily or 400 mg IV every 12 hours OR ceftazidime 2 g IV every 8 hours 1
• Consider dual active drug therapy based on clinical severity 1

Other Gram-Negative Bacilli

• Enterobacteriaceae: IV β-lactam based on susceptibilities OR ciprofloxacin 750 mg PO twice daily 1
• Enterobacter species: Cefepime 2 g IV every 12 hours OR ertapenem 1 g IV every 24 hours 1

Streptococci

• β-hemolytic streptococci: Penicillin G 20-24 million units IV every 24 hours OR ceftriaxone 2 g IV every 24 hours 1
• Vancomycin only for penicillin allergy 1

Propionibacterium acnes

• Preferred: Penicillin G 20 million units IV every 24 hours OR ceftriaxone 2 g IV every 24 hours 1
• Alternatives: Clindamycin 600-900 mg IV every 8 hours or 300-450 mg PO four times daily 1

Treatment Duration

The standard duration is 4-6 weeks of pathogen-specific IV or highly bioavailable oral antimicrobial therapy following surgical intervention. 1

• For staphylococcal infections with implant retention: Extend to 3 months for hip infections and 6 months for knee infections when rifampin is used. 1
• IV therapy can be limited to 1-2 weeks until the patient is stable and culture results are known, then transition to oral therapy with highly bioavailable agents (e.g., fluoroquinolones, linezolid). 1
• After implant removal: 6 weeks is sufficient. 1
• With implant retention: 12 weeks total duration is recommended. 1

Critical Caveats and Pitfalls

Rifampin Use

• Never use rifampin monotherapy due to rapid resistance emergence. 1
• Do not start rifampin until after thorough debridement and when wounds are dry to avoid superinfection with resistant organisms. 1
• Fluoroquinolones are the preferred companion drug for rifampin in staphylococcal infections, but never use fluoroquinolone monotherapy against staphylococci due to high failure rates. 1
• Alternative rifampin companions include TMP-SMX, minocycline, or fusidic acid (less studied). 1

Monitoring and Safety

• Monitor for QTc prolongation when using fluoroquinolones and discuss tendinopathy risk. 1
• Monitor for Clostridium difficile colitis with any antimicrobial. 1
• Adjust dosing for renal and hepatic dysfunction. 1, 3
• Follow published guidelines for outpatient IV antimicrobial monitoring. 1, 3

Surgical Considerations

• The timing of infection presentation (early ≤3 months, delayed 3-24 months, late >24 months) influences both microbiology and surgical approach. 2
• Debridement and implant retention (DAIR) has a 57% success rate in early infections but fails more often with MRSA (73% failure rate). 4
• Successful treatment requires adequate surgical debridement combined with appropriate antimicrobial therapy, as biofilm formation makes these infections difficult to eradicate. 5, 6

Chronic Suppressive Therapy

• Indefinite chronic oral antimicrobial suppression may be considered after completing initial therapy for patients unsuitable for further surgery, based on in vitro susceptibilities. 1
• For staphylococci: cephalexin, dicloxacillin, TMP-SMX, or minocycline/doxycycline 1
• Rifampin alone is not recommended for chronic suppression. 1