A Clinical Trial of Contamination of Surgical Instruments with Staphylococcus aureus During Long Time Orthopedic Surgeries

Approximately 5% of patients undergoing surgery develop surgical site infections (SSI), which prolong the length of hospital stay to 9.7 days. This study was performed aimed to determine the amount of contamination of sterile surgical instruments with Staphylococcus aureus during long time orthopedic surgeries. In This study done as a prospective study, 245 sterile surgical instruments were sampled. The contaminated samples at every hour were excluded from samples of next hour. Then, antibiotic susceptibility of Staphylococcus aureus strains was tested by 14 antibiotics using disk diffusion method according to the recommendations of CLSI. The MIC of the strains towards methicillin was tested through microdilution method, and PCR was done on mecA gene. Data and results were analyzed by chi-square statistical test and significance level was considered to be p<0/05. Out of a total of 110 specimens obtained immediately after opening the sterile covering, 5 cultures were positive (4.54%); 10 (10.98%) in 91 samples taken after surgery; 5 (15.62%) in 32 samples taken 2 hours after surgery; and 1 (8.33%) 1 in 12 samples taken 3 hours after surgery. The highest resistance of the isolates was against ceftazidime (85.71%), and all strains were sensitive to vancomycin (100%). In MIC test, 52.38% of the strains were resistant to methicillin, and 66.66% of the strains had mecA gene in the PCR method. Considering high contamination rate of surgical instruments with S. aureus, it is recommended that the covering of the sterile trays should not be opened until they are specifically needed during the procedure.