Screening for cytomegalovirus shedding in vagina and saliva: Significant differences between biological fluids, swab types and storage durations in DNA recovery

Abstract

Background: Cytomegalovirus (CMV) shedding in genital and oral secretions during pregnancy is associated with adverse outcomes. Sample collection methods between studies are not uniform and currently there are limited data on the impact of biological fluids, swab types and storage durations on the detection of CMV DNA.

Objectives: To evaluate the absorption efficiency and CMV DNA recovery of various commercially available swabs in vaginal and saliva fluids.

Study design: The absorption volume of different swab types was evaluated. The recovery of CMV DNA over time from vaginal and saliva fluids, and vaginal and saliva swabs, was evaluated by PCR measurements of samples spiked with CMV standard.

Results: Absorption efficiency of swabs varied significantly. The duration of storage did not affect CMV DNA recovery from vaginal fluid or swabs, but did significantly affect CMV DNA recovery from neat saliva fluid and saliva swabs stored dry or in viral transport media (VTM). Flocked swab/eNAT media recovered the highest amount of CMV DNA from both fluids. In saliva, flocked swab/eNAT media and polyester swab/cobas media demonstrated a higher CMV DNA recovery than foam swab/VTM. 25% of dry saliva foam swabs were falsely negative for CMV DNA.

Conclusions: Recovery of CMV DNA is dependent on sample type and swab type used. Flocked swab/eNAT media and polyester swab/cobas media appear acceptable, though flocked swab/eNAT media was superior demonstrating the best recovery of CMV DNA. For saliva, foam swabs stored dry or in VTM was shown to be inferior to flocked or polyester swabs.

Keywords: Cytomegalovirus; Saliva; Screening; Shedding; Swab; Vagina.