Microflora of Urinary Tract and Vagina

Microflora of Urinary Tract

In healthy individuals the renal calyces, pelvis, urethers, bladder and proximal parts of urethra are sterile.

In the distal part of male urethra occasional presence of Staphylococcus saprophyticus, viridans streptococci, diphtheroids, neisseriae, and some gram-negative rods is registered. In most cases they appear in this area from skin and perineum.

The female urethra is normally sterile; rarely it may contain a limited number of coccoid microflora.

Mycobacterium smegmatis and saprophytic mycoplasmal species can be ordinarily found on the mucous membranes of genitalia.

Microflora of Vagina

The first 1-2 days after birth the vagina of a newborn is sterile. The next several weeks pH of vaginal content becomes slightly acidic thereby activating the growth of lactobacilli. In some time pH value changes to neutral range and holds this level until puberty. This stimulates the growth of coccoid flora; the balance between cocci and lactobacilli supports the state of vaginal microflora this time.

At puberty lactobacilli compose a predominant part of vaginal microorganisms (Lactobacillus crispatus, Lactobacillus jensenii and others). They intensively produce acids from vaginal carbohydrates (mainly, from glycogen), thus shifting pH levels to acidic range of 4-5. Therefore, they demonstrate the evident antagonistic properties against transient vaginal bacteria including pathogenic species.

The vaginal secretion of a healthy woman has increased concentrations of glycogen and other sugars with relatively low amount of proteins; this state is maintained by normal endocrine function of ovaries. Acidification of vaginal content is an important protective condition that prevents the propagation of pathogenic and facultatively pathogenic bacteria. The established pH level of about 4.7 inhibits their growth.

During the menstrual cycle vaginal pH temporarily becomes alkaline; this fosters the progression of coccoid bacteria. They, in turn, create the favorable conditions for other groups of bacteria that may be pathogenic. Sexual activity also results in alterations of vaginal microflora with appearance of extraneous microbial representatives from outside.

Together with lactobacilli, other microbial species in various proportions may be present as part of normal vaginal microflora. Among them are group B streptococci (S. agalactiae), mycoplasmas, Gardnerella vaginalis and Mobiluncus species, anaerobic bacteria (bacteroids, prevotellas, peptostreptococci and others). In case of poor hygiene the microbes from perineal and perianal areas may appear.

Intensive antimicrobial treatment with antibiotics of broad spectrum of action can suppress normal vaginal bacteria, primarily lactobacilli, resulting in burst growth of concomitant resistant microflora. It may lead to vaginal dysbiosis, where the fungal species usually prevail. Among them are yeast-like fungi from Candida genus (e.g., C. albicans) that cause serious infectious disorder known as vaginal candidiasis.

The abrogation of protective function of lactobacilli may also trigger an excessive growth of many other vaginal microorganisms. When they start to dominate, they may develop an extensive genital non-inflammatory syndrome termed as bacterial vaginosis. It is caused by broad microbial association of Gardnerella vaginalis and Mobiluncus mulieris with non-sporforming gram-negative anaerobes (Prevotella bivia, bacteroides and some others). Above 1/3 of women may suffer from bacterial vaginosis. If not controlled, this pathology leads to serious complications, e.g. endometritis or pelvic inflammatory disease. Their progression causes profound negative effects on normal vaginal microflora.