Chapter 27 Infections of the genitourinary tract
The predominant vaginal flora in adult women consists of lactobacilli. They keep the vaginal pH low and appear to prevent the growth of potential pathogens. For instance, their suppression by antibiotics may lead to overgrowth of the yeast Candida albicans found in relatively low numbers in the healthy vagina. Other common groups of vaginal organisms include diphtheroids, streptococci, anaerobes and coliforms. Most of these organisms may behave as opportunistic pathogens when appropriate conditions supervene. Approximately 20% of women of child-bearing age carry group B β-haemolytic streptococci in the vagina. These may be acquired by a baby during its passage through the birth canal, resulting in serious infections such as meningitis and sepsis.
The urine in the bladder is normally sterile, but the voided urine often becomes contaminated by flora from the distal portions of the urethra, such as Staphylococcus epidermidis, coliforms, diphtheroids and streptococci. Additionally, in females, the organisms present in the distal part of the urethra may include contaminants from the gut flora such as enterobacteria and lactobacilli. The flushing action of the urine is arguably the most important defence factor of the urethra in both males and females. Bactericidal mechanisms in the bladder mucosa, including local antibody response and lysozyme, play an important role in preventing ascending infection of the urinary tract.
|Gonorrhoea||Neisseria gonorrhoeae (the gonococcus)|
|Vaginitis||Gardnerella vaginalis, anaerobes|
|Genital herpes||Herpes simplex virus (type 2 mainly)|
|Hepatitis Ba||Hepatitis B virus|
|AIDSa||Human immunodeficiency virus (HIV)|
|Lymphogranuloma venereum||Chlamydia trachomatis types L1–L3|
|Granuloma inguinale (donovanosis)||Calymmatobacterium granulomatis (a Klebsiella-like microorganism)|
|Pubic lice (crabs)||Phthirus pubis|
|Genital scabies||Sarcoptes scabiei|
|Non-specific urethritis||Chlamydia trachomatis types D–K|
|Vaginal thrush||Candida albicans|
AIDS, acquired immune deficiency syndrome.
A large group of infections are essentially transmitted by sexual intercourse; they may affect both heterosexual and homosexual partners. Varying patterns of sexual behaviour can result in such infections manifesting in the oral cavity, oropharynx and the rectum; sexually transmitted diseases frequently – but not invariably – produce genital lesions; several produce severe systemic disease that may even lead to death, such as human immunodeficiency virus (HIV) infection and hepatitis B.
In women: acute urethritis, increased vaginal secretions with purulent discharge. In men: acute gonococcal urethritis with severe dysuria and purulent discharge. The disease may involve the rectum and oropharynx. Pharyngitis, sore throat, tonsillitis and gingivitis may occur as a result of gonococcal infection, especially from orogenital contact in homosexual men. Asymptomatic infection is common in both men and women. Complications include prostatitis, salpingitis and occasionally haematogenous spread, causing arthritis, septicaemia and meningitis.
Gonococcal infection has been reported only in humans. The infection is limited to the mucosa of the anterior urethra in men and the cervix of women. In the newborn, gonococcal conjunctivitis may occur due to cross infection from the mother’s birth canal.
Gram smears show Gram-negative pairs of the typical kidney-shaped gonococci inside neutrophils (Fig. 27.2). Swabs from the urethra cultured on lysed blood or chocolate agar yield oxidase-positive, translucent colonies, and rapid carbohydrate utilization tests are also diagnostic (see Chapter 14).
One of the most common sexually transmitted diseases, non-specific urethritis is seen more in men than in women. It is caused by more than one agent, but Chlamydia trachomatis is the most common cause. A mycoplasmal organism (‘bacteria’ without a cell wall), Ureaplasma urealyticum, may also cause significant morbidity.
Smears and swabs of urethral or cervical discharge are diagnostic. Culture is now rarely done. Smears are examined for intracytoplasmic inclusions by immunofluorescence. Serology for chlamydial antigens by indirect immunofluorescence with monoclonal antibody or by enzyme-linked immunosorbent assay (ELISA).
Syphilis is one of the classic diseases with protean manifestations (i.e. affecting virtually all organ systems of the body), and has re-emerged as an important disease associated with HIV infection and sexual promiscuity. The disease, important due to its late and severe sequelae, is preventable, and treatable with effective and inexpensive antibiotics.