Lubricating gel influence on vaginal microbiome sampling

Gel lubrication is routinely used during gynecological examination to prevent or reduce pain, yet its impact on microbial composition during sampling remains unclear. This study aimed to investigate whether lubricating gel affects the microbial composition of vaginal samples. We included 31 pregnant women presenting during their third trimester to clinics or emergency room and collected 143 unique vaginal samples for 16S amplicon microbial analysis. Vaginal samples were obtained using sterile swabs under various conditions: without gel—immediately frozen (n = 30), with gel—immediately frozen, without gel—at room temperature (RT) for 5 h before freezing, with gel—at RT for 5 h before freezing, and additional sampling after 24 h without gel—immediate freezing. We found that sample collection with gel lubrication influenced specimen quality—half of the gel samples failing to meet processing limitation compared to those without gel. The effect of gel on testing quality dissipated after 24 h. However, when samples met post-sequencing filters, gel lubrication did not alter the microbial composition, individual taxa abundance or alpha and beta diversity. We recommend sampling either before gel exposure or 24 h after. These findings underscore the importance of considering sample collection methodologies in vaginal microbiome studies to ensure high-quality microbial data for accurate analysis.