Background Our objective was to assess the full range of cultivable microflora from pregnant women and to identify the proportion which represents novel genera or species.
Methods Vaginal swab samples from 451 pregnant women (median gestational age 25 weeks, range 9–39) were transported in an anaerobic transport device. Vaginal fluid was eluted from the swabs, serially diluted and inoculated onto 27 different pieces of culture media. Colonies were subcultured to purity and DNA was extracted. A combination of biochemical tests, 16S rDNA gene sequencing, and restriction fragment length polymorphism (RFLP) were used for identification. A vaginal smear was assessed according to the Nugent criteria.
Results A total of 5688 isolates were recovered, with a mean of 12.6 isolates per sample. Women having a Nugent score of 0–3 had a lower number of cultivable species per sample (2408/255 = 9.4) compared to women having Nugent scores of 4–6 (1168/76 = 15.4) or 7–10 (2112/120 = 17.6). A total of 305 unique bacterial species were recovered, with 62 (20%) representing novel organisms which may have previously been considered uncultivable, including Megasphaera phylotypes 1–3, novel Prevotella species, and new genera of anaerobic gram negative and positive rods.
Discussion Culture methods detect a greater diversity of microorganisms than has been previously recognised. Multiple novel bacteria will require further characterisation.
Disclosure of interest statement There are no conflicts of interest to disclose. This study was funded by the US National Institutes of Health.