Growth of Escherichia coli in Human Milk and Powdered Infant Formula under Various Treatments and Feeding Conditions in Neonatal Units

Milk supplied to neonates in neonatal units is kept at room temperature for some time, which could influence microbial growth. This study aims to evaluate the growth of Escherichia coli in HM and PIF under various treatments and conditions, as well as to determine the influence of different thawing methods on microbial growth in HM. The number of E. coli generations appearing over a 4 h period at 22 °C in HM (frozen; frozen and pasteurized; and frozen, pasteurized, and fortified) and in PIF (four brands) was determined. E. coli counts in HM inoculated and thawed using different methods were also compared. In frozen HM and in pasteurized and frozen HM, significant differences were found after 2.5 h and 1.5 h, respectively. In PIF, differences were found between 1.5 and 3 h. With regard to the thawing process, the lowest microorganism counts were obtained at 4 °C overnight; thus, it seems advisable to store milk at room temperature for a maximum of 1 h during administration in neonatal units. Thawing HM at 4 °C overnight should be the method of choice.