Solutions of Clinifeed ISO, Triosorbon, Vivonex Standard (full- and half-strength) and Vivonex HN were experimentally contaminated with two strains each of Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella aerogenes, Escherichia coli and Enterobacter cloacae at concentrations of 102-103 organisms/ml. Samples were incubated at 4,25 or 37°C and viable counts were made at 0, 4, 8 and 24 h.
No increase in numbers of any of the organisms was observed in any of the feeds during 24 h at 4°C. All organisms multiplied rapidly in Clinifeed ISO and in Triosorbon at 25 and 37°C. There was less rapid growth in half-strength Vivonex Standard at 25°C, although at 37°C all strains multiplied rapidly except for the two S. aureus strains, the growth of which was inhibited in half-strength Vivonex Standard at both 25 and 37°C. In full-strength Vivonex Standard at 25°C, only P. aeruginosa showed any increase in numbers during 24 h, whereas P. aeruginosa, K. aerogenes and E. cloacae all multiplied at 37°C. None of the test organisms multiplied in full strength Vivonex HN at any of the temperatures studied.
The results of the study show that bacteria survive and may multiply even in feeds with low pH and high osmolarity, and emphasise the importance of strict hygiene during the preparation and handling of all enteral feeds.
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