The protective bacterium in the normal vagina is:

Vagina has inhabitant bacteria called as Doderleins bacteria which is a lactobaccilli, and converts the glycogen present in vaginal epithelium into lactic acid. Thus, pH of the vagina is acidic The pH of the vagina in an adult woman is 4 -5.5 with an average of 4.5. The pH of vagina varies with age — for further details see preceding text.