Final answer:
Trichomonas is not part of the normal indigenous microbiota of the female reproductive system, whereas Lactobacillus and, to a lesser extent, Candida and E. coli are.
Step-by-step explanation:
The organism not considered part of the indigenous microbiota of the female reproductive system is C) Trichomonas.
Indigenous microbiota of the female reproductive system includes a variety of organisms that play a vital role in maintaining health. Notable are Lactobacillus species that dominate this environment for the majority of women, producing lactic acid from glycogen supplied by vaginal epithelial cells and thus maintaining an acidic pH that protects against infections. Candida, while often considered a pathogen when overgrowth occurs, is commonly present in small numbers as part of the normal flora. E. coli can be transiently present, often originating from the gut microbiota.
On the other hand, Trichomonas vaginalis is a pathogen and is not part of the normal vaginal flora. This protozoan is responsible for trichomoniasis, a sexually transmitted infection. Factors affecting the vaginal microbiota include antibiotic use, hormone levels (such as estrogen), and practices like douching that can disrupt the balance of microbes.