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 degrees 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 76.0434.08 copies/L (20-135.00 copies/L) and after freezing it was 6.75 +/- 4.34 copies/L (0.00-13.00 copies/L). 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.