Microbial Load on Instruments in 'Clean' Surgeries Reinforces Need for Antibiotic Prophylaxis

The number of orthopedic surgery cases, especially total hip and knee surgeries, has increased due to technological advances. Investigators at the University of Sao Paulo in Brazil; sought to determine the microbial load in the instruments used in clean surgeries, quantifying and identifying the genus and species of microbial growth.

Orthopedic surgical instruments were immersed after use in sterile water, sonicated in ultrasonic washer and consecutively shaken. Then, the lavage was filtered through a 0.45 micron membrane, and the result was incubated in aerobic medium, anaerobic medium and medium for fungi and yeasts.

Pinto, et al. report that i clean surgeries, results showed that 47 percent of used instruments had microbiological growth in the range of 1 to 100 CFU/instrument. The most prevalent organism was Staphylococcus coagulase negative (28 percent), followed by Bacillus subtilis (11 percent). This study refuted the hypothesis that clean surgeries happen in a microorganism-free surgery field.

The researchers say their microbiological findings reinforce the importance of antibiotic prophylaxis, practice already well established for this category of surgical procedure. Their research was presented at the International Conference on Prevention & Infection Control (ICPIC) held in Geneva, Switzerland June 29-July 2, 2011.

Reference: FMG Pinto, GADA Moriya and KU Graziano. Microbial load in instruments used in surgeries classified as clean. Presentation at International Conference on Prevention & Infection Control (ICPIC). BMC Proceedings 2011, 5(Suppl 6):P313