Enteral feeding tube guidewire—another factor in the retrograde contamination of enteral feeding systems?

Background: In vitro enteral feeding systems were used to investigate the effect that withdrawal of the guidewire from the feeding tube has on bacteria ascending from a patients’ stomach or intestine via the feeding tube to the giving set and nutrient container of the feeding system. Methods: Enteral feeding systems were assembled with the feeding tube running into nutrient broth contaminated with Klebsiella aerogenes. The enteral feeding tubes were held in different orientations (horizontal and vertical) to examine the effect in both prostrate and ambulant patients. The guidewire was removed either prior to or after the enteral feeding tube had been inserted into the K. aerogenes broth. Feed was then run through the systems for 24 h, with feed samples being collected from the distal (patient) end of the giving set at 0 and 24 h. Results: After 24 h, 10^3–108 c.f.u. (colony forming units) K. aerogenes/ml were detected in feed samples taken from the distal end of the giving set in systems where the guidewire had been removed after the enteral feeding tube had been inserted into the contaminated broth (both orientations), but K. aerogenes was not detected in samples from systems in which the guidewire had been removed before the end of the tube was inserted into the broth (both orientations). However, when the latter feed samples were enriched (i.e. incubated at 37 °C for a further 24 h to detect if very low levels of bacteria were present in the original sample), 40% of samples from systems with horizontally orientated tubes, and 20% from systems with vertically orientated tubes were positive for the test organism. K. aerogenes was not detected in any samples of feed taken from the nutrient container or just below the drip chamber. Conclusion: The results demonstrate: (i) that bacteria ascend the feeding tube over a 24-h period (retrograde contamination) and (ii) removal of the guidewire can contribute to the colonization of the lumen of the feeding tube and distal end of the giving set with bacteria from a patients’ own flora.