Evaluating bacterial contamination of the non-disposable components of the circle system within the anesthesia delivery system

One commonality among bacteria associated with Healthcare Associated Infections (HAIs) is the ability to exist on fomites. The anesthesia delivery system (ADS), commonly referred to as the anesthesia machine, has long been suspected as a source of contamination. Much of the existing research was performed prior to the development of multi-drug resistant pathogens, single use disposable components, and the current practice of re-using those same components. This study focused on the prevalence of bacterial contamination of the circle system within the ADS. An additional finding included the morphology of these contaminants. Our first hypothesis was that there will be no colony forming units (CFUs) found in the circle system of the ADS. The alternative hypothesis was that there will be CFUs found in the circle system of the ADS. Our second hypothesis was that there will be no differences in the number of CFUs found at different sampling locations of the ADS at 24 hours incubation. The alternative hypothesis was that there will be differences in the number of CFUs found at different sampling locations of the ADS at 24 hours incubation. Our third hypothesis was that there will be no differences in the number of CFUs found at different sampling locations of the ADS at 48 hours incubation. The alternative hypothesis was that there will be differences in the number of CFUs found at different sampling locations of the ADS at 48 hours incubation.;A total of 92 samples were obtained from multiple ports from eight different ADSs. ADSs were selected from a community hospital following a full day's use, including at least one general anesthetic with either an endotracheal tube (ETT) intubation or laryngeal mask airway (LMA) placement. These samples were swabbed onto petri-plates, incubated, and analyzed for number and morphology of CFUs following 24 and 48 hours of incubation.;The results yielded an average CFU count of 12.34 at 48 hours incubation. A one-sample t test indicated that the number of CFUs was significantly greater than zero (p =0.004). There were significant differences in CFU counts between swabbing locations within the circle system at 24 hours incubation (p = 0.041) but this was not the case at 48 hours incubation (p = 0.133). The average number of CFUs at 24 hours incubation was 38.13 for the expiratory port and 0.13 for the inspiratory port. Both gram negative and gram-positive bacteria were identified. This pilot study revealed that the circle system of the ADS is contaminated with a mixture of flora. The level of contamination was highest at the expiratory port.;(Key Words: anesthesia delivery system, healthcare associated infections, colony forming units, contamination)...