Stability of the Antimicrobial Capacity of Human Milk Against Cronobacter Sakazakii During Handling

Abstract

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.

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

“…In HMBs, milk is frozen for long periods for a maximum of two times (before and after pasteurization), but it is also pasteurized. According to the results of the present work, the E. coli generation times were significantly reduced (p = 0.012) when the milk was frozen and pasteurized; thus, the time at which the differences in the counts were obtained was reduced to 1.5 h. Various authors [7,8] have shown that pasteurization significantly reduces the bactericidal capacity of HM, and according to the studies by Paulaviciene [28] and Arroyo [29], pasteurization and freezing/thawing processes cause a significant loss of lactoferrin, lysozyme, IgG, and IgA, components with important antibacterial activity, which could explain the reduction of this capacity in HM subjected to these treatments. It is evident that the pasteurization process ensures the absence of pathogenic microorganisms in the milk that is supplied to the infant, but if milk contamination occurs during subsequent handling, microorganisms could multiply when the milk supply is kept at room temperature.…”

“…Moreover, is important to consider the freezing time, as longer times (3 months) affect the antimicrobial capacity of the HM [8] and could allow for faster microbial growth under NICU conditions.…”

“…In addition, it must be considered that treatments such as freezing and pasteurization can affect the antimicrobial capacity of milk [7][8][9]. Preterm infants are an extremely vulnerable population; therefore, it is essential to control hygiene during all treatments and handling of HM, as well as powdered infant formula (PIF), which is used as an alternative in some cases [8].…”