Microbiology of infected arthroplasty: implications for empiric peri-operative antibiotics

Area of Science:

• Orthopedic Surgery
• Microbiology
• Infectious Diseases

Background:

• Periprosthetic joint infections are a significant complication of hip and knee arthroplasty.
• Understanding the spectrum of causative organisms and their antibiotic susceptibility is crucial for effective treatment.

Purpose of the Study:

• To characterize bacterial isolates from infected hip and knee arthroplasty specimens.
• To determine antibiotic susceptibility patterns of these isolates.
• To recommend optimal empiric peri-operative antibiotic regimens.

Main Methods:

• Prospective collection of specimens from revision hip and knee arthroplasties between January 1999 and August 2006.
• Identification of micro-organisms and antibiotic susceptibility testing.
• Analysis of 248 micro-organisms from 147 patients with positive specimens.

Main Results:

• Staphylococcus species were the most common isolates (53%), followed by Gram-negative bacteria (24%).
• Gram-positive organisms were detected within 96 hours, and Gram-negative organisms within 48 hours.
• 46% of all isolates were susceptible to cephalothin; only 35% of coagulase-negative staphylococci were sensitive.

Conclusions:

• Empiric antibiotic prophylaxis for revision hip and knee arthroplasty should include vancomycin to cover Gram-positive bacteria.
• Gentamicin should be included to provide coverage for most Gram-negative bacteria.