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.
METHODS AND MATERIALS
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.
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).
The study showed that the freeze-thawing method is an effective method in reducing the CMV load in breast milk samples.