Breastmilk cultures and infection in extremely premature infants

Objective: As expressed mother's milk (MM) is known to be colonized by microbial species, it is occasionally considered as a source of infection in premature infants, prompting some clinicians to obtain milk bacterial culture results before infant feeding. To determine whether serial microbial cultures of MM predict infection in premature infants. Study Design: Milk microbial flora was determined by plate counts from aliquots of MM obtained from 161 mothers of infants born < 30 weeks gestation (n = 209). Pathogens isolated from the same infant were tabulated. Result: Milk samples (n = 813) yielded 1963 isolates. There were no relationships between microbial counts and maternal age, ethnicity, education, skin-to-skin contact and infant infection. In 64 infants, milk and pathological isolates had presumptively the same Gram-positive organism, yet the odds of infection before or after exposure to milk containing that Gram-positive organism were not significant (1.18; 95% confidence interval = 0.51, 2.76). In eight infants, milk and pathological isolates had presumptively the same Gram-negative organism, which appeared sporadically in milk, either before or after isolation in the infant. Conclusion: Results of initial milk cultures do not predict subsequent culture results. Random milk cultures, even if obtained at any time during hospitalization, are not predictive of infection in premature infants. The sporadic nature of the appearance of certain isolates, however, suggests common exposure of both mother and infant. Routine milk cultures do not provide sufficient data to be useful in clinical management. Journal of Perinatology (2011) 31, 335-338; doi:10.1038/jp.2011.13; published online 24 February 2011