Detection of hydrogen peroxide-producing Lactobacillus species in the vagina: a comparison of culture and quantitative PCR among HIV-1 seropositive women

Background: The presence of hydrogen peroxide (H₂O₂) producing Lactobacillus in the vagina may play a role in controlling genital HIV-1 shedding. Sensitive molecular methods improve our ability to characterize the vaginal microbiota; however, they cannot characterize phenotype. We assessed the concordance of H₂O₂-producing Lactobacillus detected by culture with quantitative PCR (qPCR) detection of Lactobacillus species commonly assumed to be H₂O₂-producers.Methods: Samples were collected as part of a prospective cohort study of HIV-1 seropositive US women. Cervicovaginal lavage specimens were tested for L. crispatus and L. jensenii using 16S rRNA gene qPCR assays. Vaginal swabs were cultured for Lactobacillus and tested for H₂O₂-production. We calculated a kappa statistic to assess concordance between culture and qPCR.Results: Culture and qPCR results were available for 376 visits from 57 women. Lactobacilli were detected by culture at 308 (82%) visits, of which 233 of 308 (76%) produced H₂O₂. L. crispatus and/or L. jensenii were detected at 215 (57%) visits. Concordance between detection of L. crispatus and/or L. jensenii by qPCR and H₂O₂-producing Lactobacillus by culture was 75% (kappa = 0.45).Conclusions: Among HIV-1 seropositive women, there was a moderate level of concordance between H₂O₂-producing Lactobacillus detected by culture and the presence of L. crispatus and/or L. jensenii by qPCR. However, one-quarter of samples with growth of H₂O₂-producing lactobacilli did not have L. crispatus or L. jensenii detected by qPCR. This discordance may be due to the presence of other H₂O₂-producing Lactobacillus species.