Evaluation of the Freeze-Thawing Method in Reducing Viral Load of Cytomegalovirus in Breast Milk of Mothers of Preterm Infants.

Background: The aim of this study was to evaluate the freeze-thawing method in reducing viral load of cytomegalovirus (CMV) in breast milk of mothers of preterm infants.
Materials and Methods: In this study, 169 nursing mothers of preterm infants were evaluated serologically for CMV infection. We found 29 (17.15%) nursing mothers who had serologic evidence of CMV infections consistent with recent infection (N = 2, IgG + IgM +) or prior infection (N = 27 IgG + IgM-). Two to 6 weeks after delivery, breast milk of seropositive mothers (N = 29) was evaluated for CMV load by real-time polymerase chain reaction (PCR) before and after freezing at -20°C for 72 hours. All preterm infants with milk results positive for DNA particles of CMV (N = 25) were followed up for signs and symptoms of CMV infection until 3 months of age, together with urine testing for CMV by real-time PCR.
Results: Examination of breast milk by real-time PCR of the seropositive mothers showed 25 of them with CMV DNA particles in their breast milk. After freezing and thawing, we found virus DNA in 4 of 25 (16%) of the breast milk samples and there was no CMV DNA particles in 21 (84%) of them. In these samples, mean viral load before freezing was 76.04 ± 34.08 copies/μL (20-135.00 copies/μL) and after freezing it was 6.75 ± 4.34 copies/μL (0.00-13.00 copies/μL). Freezing showed a significant decrease in viral load of the samples (p = 0.001).
Conclusion: The study showed that the freeze-thawing method is an effective method in reducing the CMV load in breast milk samples.