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 (H(2)O(2)) 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 H(2)O(2)-producing Lactobacillus detected by culture with quantitative PCR (qPCR) detection of Lactobacillus species commonly assumed to be H(2)O(2)-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 H(2)O(2)-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 H(2)O(2). 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 H(2)O(2)-producing Lactobacillus by culture was 75% (kappa = 0.45). CONCLUSIONS Among HIV-1 seropositive women, there was a moderate level of concordance between H(2)O(2)-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 H(2)O(2)-producing lactobacilli did not have L. crispatus or L. jensenii detected by qPCR. This discordance may be due to the presence of other H(2)O(2)-producing Lactobacillus species.