Fortifying fresh human milk with commercial powdered human milk fortifiers does not affect bacterial growth during 6 hours at room temperature

Objective To evaluate the growth of resident aerobic mesophilic flora and added Enterobacter sakazakii in fresh unfortified human milk; fresh human milk fortified with two commercial powdered fortifiers differing in iron content; and infant formula prepared from powder. Subjects Eight mothers provided preterm breast milk samples. Methods Breast milk samples were divided into three aliquots: unfortified, fortified with fortifier containing 1.44 mg iron/14 kcal, and fortified with fortifier containing 0.4 mg iron/14 kcal. Aliquots of formula were prepared. Breast milk and formula aliquots were divided into two test samples. Half were inoculated with low amounts of E sakazakii; half were not. All test samples were maintained at room temperature (22 degrees C), serially diluted, and plated onto agars after 0, 2, 4, and 6 hours. Plates were incubated at 35 degrees C and enumerated. Statistical analyses Data were analyzed using repeated measures analysis of variance. P <.05 was considered significant. Results There were no differences in colony counts of aerobic bacteria among uninoculated or among inoculated human milk samples at any time; counts did not increase significantly over 6 hours. There were no differences in colony counts of E sakazakii among inoculated human milk samples at any time; counts did not increase significantly over 6 hours. Aerobic bacteria and E sakazakii colony counts from infant formula did not increase significantly over 6 hours. Conclusions During 6 hours at 22 degrees C, fresh human milk and formula had negligible bacterial growth; fortifying human milk with powdered fortifiers did not affect bacterial growth.