27: Infections of the genitourinary tract

Chapter 27 Infections of the genitourinary tract

Normal flora and the natural defences 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.

Important pathogens

Important pathogens are listed in Figure 27.1 and Table 27.1.

Table 27.1 Sexually transmitted diseases

Disease Agent
Bacterial infections  
Gonorrhoea Neisseria gonorrhoeae (the gonococcus)
Syphilis Treponema pallidum
Vaginitis Gardnerella vaginalis, anaerobes
Chancroid Haemophilus ducreyi
Viral infections  
Genital herpes Herpes simplex virus (type 2 mainly)
Genital warts Papillomavirus
Hepatitis Ba Hepatitis B virus
AIDSa Human immunodeficiency virus (HIV)
Others  
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
Trichomoniasis Trichomonas vaginalis
Vaginal thrush Candida albicans

AIDS, acquired immune deficiency syndrome.

a Not always sexually transmitted.

Sexually transmitted diseases

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.

Gonorrhoea

Gonorrhoea is caused by Neisseria gonorrhoeae (the gonococcus).

Diagnosis

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).

Jan 4, 2015 | Posted by in General Dentistry | Comments Off on 27: Infections of the genitourinary tract
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