2. Universidad Cardenal Herrera-CEU

Background: Neonatal infections with Cronobacter sakazakii have recently been associated with the consumption of expressed human milk. Study Aims: (1) To evaluate whether human milk has antimicrobial capacity against C. sakazakii and (2) to determine the stability of its capacity when it is subjected to various treatments. Methods: The antimicrobial capacity of human milk against C. sakazakii was evaluated using an observational, cross-sectional, comparative design. Mature human milk samples (N = 29) were subjected to different treatments. After incubation at 37°C for 72 hr, samples were compared with fresh milk on the stability of their antimicrobial capacity. Two-way analysis of variance (ANOVA) was performed. Results: In fresh milk, counts of C. sakazakii were reduced by 47.26% (SD = 6.74) compared to controls. In treated milk, reductions were: refrigeration at 4°C for 72 hr (M = 33.84, SD = 13.84), freezing at –20°C for 1, 2, and 3 months (M = 40.31, SD = 9.10; M = 35.96, SD = 9.39; M = 26.20, SD = 13.55, respectively), Holder pasteurization (M = 23.56, SD = 15.61), and human milk bank treatment with (M = 14.37, SD = 18.02) and without bovine fortifier (M = 3.70, SD = 23.83). There were significant differences (p < .05) between fresh and treated milk. Conclusions: Human milk has antimicrobial capacity against C. sakazakii. However, its capacity is negatively influenced by common preservation and hygienization methods. Milk should be stored refrigerated for a maximum of 72 hr or frozen for a short period of time.

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.