Bacterial species in the vaginal microbiome correlated by Nugent score: cross-sectional data from the Microbicide Safety Biomarkers Study in Kenya, Rwanda, and South Africa

Background: Increasingly, research is being conducted to define the characteristics of a normal healthy vaginal microbiome and predict development of disturbances. Studies performed in African women are scarce and knowledge about their healthy normal microbiome is lacking. Methods: Women were recruited in three African countries and followed up over seven visits. Each visit, vaginal specimens were examined using Nugent score and analyzed by quantitative PCR to detect and quantify Lactobacillus species, Gardnerella vaginalis (GV) and Atopobium vaginae (AV). The preliminary baseline data are presented. Results: Out of 376 women, 208 (55.3%) had a Nugent score 0 (normal), 29 (7.7%) a score 4-6 (intermediate) and 130 (34.6%) a score of 7-10 (BV). Nugent score was associated with a significant difference in prevalence of species (p<0.001); except for L. gasseri (p=0.044). Almost all (99.5%) women with normal microbiome harboured Lactobacillus: L. iners (84.1%) and L. vaginalis (43.8%) were frequently detected; L. crispatus (34.1%), L. jensenii (27.9%) and L. gasseri (11.1%) were less prevalent. GV and AV were detected in 28.4% and 13.5%, respectively. Conversely, in women with BV, GV (93,8%) and AV (82.3%) were frequently present, but Lactobacillus less frequent (L. jensenii and L. gasseri 3.8%; L. crispatus 6.2%; L. vaginalis 6.9%; L. iners 66.9%). The qPCR results of the intermediate group were all between the results of the normal microbiome and BV except for L. iners, detected in 62.1%. Conclusion: As expected, women suffering from BV (as determined by Nugent scoring) frequently harboured GV and AV. L. iners was most often present overall. We detected L. vaginalis more often than L. crispatus, especially in the normal microbiome, which is in contrast with previous studies. However, when L. crispatus was present, counts were almost always high (>106/ml). In contrast, for L. vaginalis, counts were high in less than half of the cases