ENDOGENOUS BACTERIAL-CONTAMINATION OF ENTERAL TUBE-FEEDING SYSTEMS DURING ADMINISTRATION OF FEEDS TO HOSPITAL PATIENTS

The use of sterile, prepackaged enteral feeds has helped to reduce the risk of exogenous microbial contamination of enteral feeds but there is increasing evidence that endogenous contamination with bacteria fro m the patient's own flora may occur. The purpose of this study was to compare the levels and types of micro-organisms present in residual fe ed in nutrient containers and giving sets when either 500 or 1000 ml p refilled, ready-to-hang nutrient containers were used to administer 10 00 and 2000 ml quantities of feed to patients on hospital wards over 2 4 h using a single giving set over this period. Forty-one adult patien ts were randomly allocated to receive either 1000 or 2000 ml of steril e undiluted, whole protein feed over 24 h from 1000 ml prefilled conta iners (Nutrison Steriflo, Cow and Gate Nutricia Ltd) or from 500 ml pr efilled bottles (Osmolite, Abbott Laboratories Ltd). One giving set wa s used over 24 h far each patient. Samples of feed from the nutrient c ontainers and the distal end of each. giving set were sent for microbi ological analysis immediately after removal from the patient. Control experiments demonstrated that there were no micro-organisms in the uno pened feed containers and that none was introduced during the feed sam pling procedure. The percentage of days on which feed samples from the nutrient containers were contaminated was < 10% for feeds administere d at a rate of 1000 ml over 24 h and less than or equal to 23% for tho se administered at a rate of 2000 ml over 24 h irrespective of system, which may be attributed to increased handling of systems and reuse of the giving set. However, the percentage of days on which samples from the giving sets were contaminated was greater than or equal to 43% fo r all systems. In fact, on an average of 33% of days it was found that the only feed sample that was contaminated was that collected from th e giving set. Counts for these samples were greater than or equal to 1 0(3) cfu/ml and the main bacteria isolated included Klebsiella spp., E nterobacter spp., Escherichia coli, Streptococcus faecalis and Pseudom onas aeruginosa. These results further implicate retrograde spread of the patient's own nora as a possible source of microbial contamination of feed in the giving sets of enteral feeding systems.