Knee samples will be serially diluted in a sterile phosphate buffer in ten-fold dilutions to 10-3 for pre-disinfection samples and 10-1 for post-disinfection samples. Aliquots of 100-200 microliters of each diluted and undiluted specimen is then spread in duplicate on 5% blood agar plates. All plates are then aerobically incubated for 36-48 hours at 35 degrees Celsius. The air-inoculated plates and negative control plates are incubated along with the knee samples for 36-48 hours at 35 degrees Celsius.