Study: Prevotella bivia grows more in high pH (BV)

Prevotella bivia is a gram-negative anaerobic species of bacteria that can cause or are associated with pelvic inflammatory disease and bacterial vaginosis. Species in the Prevotella family are known to cause respiratory, mouth and vaginal infections, but some species also reside harmlessly in the gut.

P. bivia is a pH-sensitive microbe. In this study of P. bivia, the following was observed:

  • pH 6.0 – CFU (colony-forming units) was 7.93 per ml
  • pH 5.5 or 5.0 – CFU decreased by 1.39 CFU/ml/day

In observations of over 2,000 women, P. bivia was frequently isolated as a commensal in healthy, non-pregnant fertile-aged women. Prevotella spp. was identified as one of five major factors that could be used to calculate the likelihood that any given microbiota is within the ‘normal’ range. This was an unexpected finding, since P. bivia is typically present in 100-times less than other numerically dominant organisms.

Bacterial vaginosis is typically diagnosed using three out of four of the following tests: high pH (alkaline, over 4.5), fishy odour, thin discharge, and clue cells. The number of species that appear to be associated with BV are many and varied, which has made figuring out exactly which bacteria to target with treatments difficult, and antibiotic treatment is hit and miss. About half of all BV treatment fails using antibiotics.

Women with BV tend to have different vaginal microbiomes than healthy vaginas, with the BV vagina dominated by anaerobic gram-negative rod bacteria like Prevotella spp., Gardnerella vaginalis, Peptostreptococcus spp., Mycoplasma hominis, Ureaplasma urealtyticum, and Mobiluncus spp. in much higher concentrations than in asymptomatic women. Almost all women with BV have been found to carry at least one Bacteroides isolate.

The Effect of pH on Growth and Succinate Production by Prevotella bivia, V. Pybus & A. B. Onderdonk, Microbial Ecology in Health and Disease Vol. 9 , Iss. 1,1996