Vaginal flora composition

Community state types (CST) of the vaginal flora: CST I (L. crispatus) through to CST IV (diverse, few lactobacilli). How this is to be read is set out in your findings report.

What the vaginal flora composition shows

The analysis uses bacterial genetic material to determine which bacteria predominate in the vagina. Alongside CST I with Lactobacillus crispatus and CST IV without predominant lactobacilli, there are CST II (L. gasseri), CST III (L. iners) and CST V (L. jensenii). Lactobacilli ferment sugar building blocks released from the glycogen in the lining cells into lactic acid. How much glycogen the lining stores is controlled by oestrogens. That is why the composition changes over the course of life – at puberty, during the cycle, in pregnancy and after the menopause – and can also fluctuate from day to day, for example during menstruation.

How a lactobacillus-rich vaginal flora protects the mucosa

Lactic acid keeps the pH low. In this acidic form it penetrates bacteria and viruses and inhibits them, and in cell experiments it also dampened inflammatory reactions of the mucosa. Lactobacilli also produce antibacterial proteins and occupy binding sites where other germs would otherwise settle. The species differ: L. crispatus produces both forms of lactic acid, L. iners only one of them, plus a cell-damaging protein. In studies, L. iners was found more often during transitions to a flora poor in lactobacilli and is therefore regarded as less stable.

What happens when lactobacilli are lacking in the vaginal flora?

If lactobacilli are largely absent, bacteria that do not need oxygen, such as Gardnerella, Prevotella or Fannyhessea, take over. The pH rises, amines are formed, the protective mucus layer is broken down, and in some women more inflammatory messengers are produced. In studies, such a flora has been linked with bacterial vaginosis, greater susceptibility to sexually transmitted infections and premature births. At the same time, CST IV also occurs in many women without any complaints, and its share differs between population groups in studies – a flora poor in lactobacilli is not in itself a disease.