Analysis of Thermal Sensitivity of Human Cytomegalovirus Assayed in the Conventional Conditions of a Human Milk Bank

Abstract

One of the main concerns in human milk banks (HMB) is the transmission of human cytomegalovirus (HCMV) that could be present in the milk of infected women. There are consistent data showing that this virus is destroyed by Holder pasteurization (62.5°C for 30 min), but there is a lack of information about the response of the virus to the treatment at lower temperatures in strict HMB conditions. In order to analyze the effectiveness of different temperatures of pasteurization to eliminate HCMV in human milk, a preliminary assay was performed incubating HCMV-spiked raw milk samples from donor mothers at tested temperatures in a PCR thermocycler and the viral infectivity was assayed on cell cultures. No signs of viral replication were observed after treatments at temperatures equal or >53°C for 30, 20, and 10 min, 58°C for 5 min, 59°C for 2 min, and 60°C for 1 min. These data were confirmed in a pasteurizer-like model introducing HCMV-spiked milk in disposable baby bottles. No viral infectivity was detected on cell cultures after heating treatment of milk for 30 min at temperatures from 56 to 60°C. Thus, our results show that by using conventional pasteurization conditions, temperatures in the range of 56–60°C are enough to inactivate HCMV. Consequently, we consider that, in order to provide a higher quality product, the current recommendation to pasteurize both mother's own milk and donated milk at 62.5°C must be re-evaluated.

Examining Evidence of Benefits and Risks for Pasteurizing Donor Breastmilk

“…Certainly, substantial time, energy, and resources would be required to compile and assess the complex microbial evidence published even in the most recent decade as relates to policy decisions about pasteurization. A recent study [40] documenting effectiveness of antiviral activity for various thermal treatments of donor milk spiked with CMV (temperatures from 48 • C to 63 • C, times from 1 to 30 min) recommended that current policies specifying conventional Holder pasteurization be re-evaluated. It is unclear at present what risk management strategies might provide an optimal balance between maximizing benefits and minimizing risks to neonates.…”

Perinatal Cytomegalovirus Infection

“…Holder pasteurization consists of heating at 62.5 °C for 30 min, effectively inactivates CMV as well as other potential pathogens, and is currently recommended for banking of human milk as well as for regular feeding preterm of infants [ 102 ]. However, pasteurization is reported to have greater negative impacts compared with freezing on host defense proteins in milk, as well as on numerous cytokines, hormones, and growth factors [ 103 ].…”