Abstract
Background: Infants can acquire primary postnatal CMV infection from the breast milk of their CMV infected mothers(1). About 60% of Australian mothers are CMV positive. Most of these will eventually excrete CMV into their breast milk(1). CMV transmission has been documented in 37% of preterm infants of CMV infected mothers(1) -symptomatic infection such as neutropenia, thrombocytopenia, hepatopathy, sepsis-like deterioration occurred in about half of these (1). The infants most at risk of symptomatic infection are the extremely low birth weight infants and those who acquire CMV early(2). An increased risk of adverse neurodevelopmental outcome in low-birth weight infants who acquired CMV early has been suggested (3). Preventing CMV transmission in extremely preterm infants from maternal milk is a clinical problem. Methods that reliably remove CMV such as heating also remove beneficial properties of breast milk. Freezing is not harmful to the protective effects of breast milk. Previous small studies of freezing (to −20°C) breast milk with naturally acquired CMV showed a reduction in CMV titres, or elimination of CMV. These studies used a culture method with a low sensitivity.
Aim: A pilot study using a sensitive culture method, to determine the length of freezing at −20°C required to eliminate CMV from breast milk. Methods: Breast milk was collected from CMV seropositive women. The breast milk was frozen in 1 ml aliquots at −20°C in a quality-controlled freezer. CMV culture was performed at day 0,1,3,5,7,10 and 14 after freezing. CMV was cultured in human embryonic fibroblasts in tube cultures and monitored for the characteristic CMV cytopathic effect. Immunofluorescence with CMV-specific monoclonal antibodies gave a sensitive measure of the presence of CMV. CMV culture was chosen as the endpoint as it is the marker of CMV infectivity. PCR, while more sensitive, does not necessarily indicate infectivity.
Results: Breast milk was collected on one occasion from 19 women, PCR detected CMV in 12, CMV was cultured in 5 of these samples. After 7 days of freezing at −20°C CMV could not be cultured in any of the samples.
Conclusion: We recommend freezing breast milk to −20°C for 7 days is a relatively simple method to substantially reduce the CMV infectivity of breast milk for extremely preterm infants.
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Sharp, M., Carrello, A., McMinn, P. et al. 237 Reducing The CMV Infectivity of Mother's Own Breast Milk. Pediatr Res 56, 504 (2004). https://doi.org/10.1203/00006450-200409000-00260
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DOI: https://doi.org/10.1203/00006450-200409000-00260
