P1098 BACTERIAL GROWTH RATES IN HUMAN MILK CONTAINING POWDERED FORTIFIERS

Abstract

Introduction: While commercially sterile liquid formulas should be used for feeding preterm infants, most commercial human milk fortifiers are powdered. New guidelines indicate that fortified human milk may be fed for up to 4 hr after preparation, although no data have validated this recommendation. This study was designed to assess growth rates of Enterobacter sakazakii and resident aerobic flora from human milk during a 6 hr incubation in standard preterm formula and fresh human milk with and without powdered fortifiers. Methods: Eight mothers of preterm infants provided fresh samples of expressed milk. Samples were refrigerated immediately and processed within 24 hr. Aliquots of human milk were mixed with one of two commercial fortifiers according to label instructions (1 packet per 25 ml). Aliquots of preterm formula, human milk, and fortified human milk were divided into 2 samples; one sample was inoculated with 103 cfu/ml E. sakazakii and the other was not. All samples were incubated at room temperature; colony counts of E. sakazakii and total aerobic bacteria were enumerated at baseline (0 hr), 2, 4, and 6 hr, using selective Violet Red Bile Glucose Agar and non-selective Trypticase Soy Agar (TSA). Data were analyzed using repeated measures of analysis of variance. Results: Fresh human milk had higher counts of aerobic bacteria than did preterm formula or fortifiers. After controlling for milk or formula, culture media, and inoculation method, overall bacteria counts from 0 to 4 hr increased 0.16 log cfu/ml. The effect of time on bacterial counts was similar for all factors. Representative data for resident flora in human milk samples (TSA) are shown:Table 1: Number of Bacteria (log cfu/ml; mean ± SE)Conclusion: Bacterial growth in expressed human milk containing powdered fortifiers is similar to growth in human milk alone, with negligible changes occurring up to 6 hr. These data support current guidelines that recommend using fortified human milk for up to 4 hr after preparation.