Aspiration (of gastric residuals) - A cause of bacterial contamination of enteral feeding systems?

In vitro model enteral feeding systems were used to investigate whether bacteria can travel from the 'patient's' stomach or intestine via the enteral feeding tube to the giving set and nutrient container of the feeding system when feed is flowing continuously through the system for 24 h. Further systems were also assembled to examine the effects that aspiration and flushing via the enteral feeding tube and/or the medication (Y) port have on the bacterial contamination of feed and feeding systems. Organisms were detected at levels ranging from 10(2)-10(9) CFU/ml (CFU, colony forming units) in feed samples collected from the distal end of the giving set at 0 h immediately after aspirating or aspirating and flushing. Fewer bacteria (10(2)-10(5) CFU/ml) were recovered at 0 h in samples from systems where aspiration or aspiration and flushing were carried out via the tube as compared with those where aspiration and flushing took place via the mediport (10(6)-10(9) CFU/ml). No bacteria were detected at 0 h in samples from systems that had neither been aspirated nor flushed. The test organism, Klebsiella aerogenes was recovered from all samples taken from the distal ends of the giving sets after 24 h. The systems which were neither aspirated nor flushed yielded more variable levels of contamination (10(4)-10(8) CFU/ml). The remainder of the systems, which had been subjected to some combination of aspirating and hushing, had more consistent levels of contamination (10(6)-10(8) CFU/ml) after 24 h. At no time during the study were K. aerogenes organisms detected in samples of feed taken from the nutrient container or just below the drip chamber at 24 h. The results of this study confirm the hypothesis that one of the contributory factors in the microbial colonisation of enteral feeding tubes and giving sets with organisms from the patients' own nora is the practice of aspirating the stomach or intestinal contents to check the position of the tube.