The Effect of Storage Time on the Growth of Microorganisms in Pasteurized and Unpasteurized Donor Human Milk in a Tertiary Hospital in Davao City: A Quasi-Experimental Study

Abstract

Background: Donor Human Milk (DHM) is the recommended food of infants whenever mom’s own milk (MOM) is not available. However, due to the pathogenic microbiological component of DHM, concerns on the safety of the milk are inevitable. Objective: To determine the effect of storage time on the microbial growth of pasteurized and unpasteurized Donor Human Milk maintained at a constant temperature of -20°C. Methodology: This is a Quasi-experimental Research done in the Newborn Care Unit (NCU) and Bacteriology Section of a private tertiary hospital in Davao City. The effect of storage time to the microbial growth of pasteurized and unpasteurized DHM was determined using Friedman Test 2-way Analysis of Variance by Ranks. Pairwise comparison of microbial growth between pasteurized and unpasteurized DHM at different storage times was determined using the Mann-Whitney U test. Results: Baseline DHM samples had moderately heavy bacterial growth of Staphylococcus epidermidis. There was a decrease from moderately heavy to light growth of the same species in the 24-hour storage time for both pasteurized and unpasteurized DHM. Pasteurized DHM did not have any microbial isolates at 48h, 72h, 4w, 8w and 12w while unpasteurized DHM had Acinetobacter baumanii, Staphylococcus warneri, Kocuria kristinae, and Staphylococcus saprophyticus growths. The analysis revealed that there is a statistically significant difference in the microbial growth in both pasteurized and unpasteurized DHM samples when stored at different times, χ2 (6) = 28.457, p = 0.00. Conclusions: Storage time significantly interacts with the microbial growth on both pasteurized and unpasteurized DHM samples. Therefore, microbial growth in DHM samples may be affected by the length of time stored at a constant temperature of -20°C. Pasteurized DHM samples when stored at -20°C for more than 48 hours resulted to a statistically reduced microbial growth.