Molecular epidemiology of cytomegalovirus infections in premature twin infants and their mother.

Premature identical twins are described who according to molecular fingerprinting of their viral isolates, demonstrate a nonmaternal nursery source for their acquired cytomegalovirus (CMV) infections. The babies were born via cesarean section at 29 weeks gestation. Weekly urine screening of the infants indicated that at birth both were CMV-negative. Twin B developed CMV at 6 weeks of age, while Twin A developed his infection when he was 9 weeks old. Three months following delivery cervical and urine cultures of the infants' mother were negative and she had no detectable CMV antibody. At 6 months postpartum (2 months following both infants' discharge home) a repeat urine culture of their mother was positive for CMV, and here CMV-CF titer had risen to 1:128. DNA fingerprinting by restriction endonuclease digestion analyses of the viruses isolated from the two infants indicate that they were infected with different strains of CMV. In addition the DNA fingerprinting pattern of the mother's isolate is identical to that of Twin A. These cases give further evidence that hospitalized infants may acquire CMV from hospital sources and document by molecular fingerprinting for the first time to our knowledge that these babies may transmit the virus to CMV-seronegative individuals. This study also demonstrates how restriction endonuclease digestion analyses can be used as a powerful tool to study the epidemiology of CMV infections.