With the exception of female urethra and vagina, the genito-urinary tract is generally sterile. The ureters, kidneys, prostrate, and cervix are normally sterile. The female urethra is colonized with large number of lactobacilli, streptococcal species, and coagulase-negative staphylococci. Fecal organisms, such as E. coli, Enterococcus spp., and Candida spp. can also colonize thefemale urethra, which is transient.
The microbial flora in the vagina is more numerous and diverse. Lactobacilli are the predominant organisms with most commonly isolated species being Lactobacillus acidophilus, Lactobacillus fermentum, Lactobacillus casei, and Lactobacillus cellobiosus. Other anaerobes commonly isolated from thevagina are Bifidobacterium, Peptostreptococcus, Porphyromonas, and Prevotella species.
Actinomyces species are believed to be present in the vaginabecause they are associated with vaginal infections. Actinomycesisraeli is the most common Actinomyces species associated with gen-ital actinomycotic infections. Propionibacterium and Mobiluncus spp. are also present in the vagina.
The aerobic bacteria present in the vagina include coagulase-negative Staphylococcus, Streptococcus (viridans group and beta-hemolytic strains), Corynebacterium spp., Gardnerella vaginalis, Neisseria spp., Haemophilus spp., and members of Enterobacteriaceae.Three species of nonpathogenic Treponema (Treponema phagede-nis, Treponema refringens, and Treponema minutum) are found invaginal specimens. Six species of Mycoplasma and Ureaplasma are common inhabitants of vagina, which have pathogenic potential. The flagellate Trichomonas vaginalis is present in small numbers in healthy women. Candida species and Torulopsisglabrata are common members of the microbial flora of vagina.