Levels of microbial contamination on surgical instruments

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To ascertain the microbial load and type of organisms on used surgical instruments following standard cleaning, which consisted of the use of a washer sterilizer followed by sonic cleaning.


In this prospective experimental study, used surgical instruments were immersed in Peptamin Tween broth, the broth agitated, and then filtered through a 0.45 [micro sign]m filter. Quantitative cultures were performed, and all microbes were identified by using standard techniques.


This study was conducted at a 660-bed university hospital.


The microbial load remaining on used surgical instruments after cleaning was as follows: 36 (72%) instruments 0 to 10 colony-forming units (CFU), 7 (14%) instruments 11 to 100 CFU, and 7 (14%) instruments >100 CFU. Organisms contaminating the instruments included coagulase-negative staphylococcus (56%) followed by Bacillus (22%) and diphtheroids (14%). No other microbes were isolated from more than 4% of the instruments.


Most used nonlumen surgical instruments contain less than 100 CFU of relatively nonpathogenic microorganisms after cleaning. This suggests that new low-temperature sterilization technologies are likely to be highly effective in preventing cross-transmission of infection via nonlumen medical instruments. (AJIC Am J Infect Control 1998;26:143-5.)

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