The urogenital system is a combination of the urinary tract and reproductive system. Because both systems are open to the external environment, they are prone to infections. Some infections are introduced from outside, whereas others result from imbalances in the microbiota of the urogenital tract.
Urinary tract infections (UTIs) are one the most common bacterial infections worldwide, affecting over 100 million people each year. During 2007 in the United States, doctor office visits for UTIs exceeded 10 million, and an additional 2–3 million emergency department visits were attributed to UTIs. Sexually transmitted infections (STIs) also primarily affect the urogenital system and are an important cause of patient morbidity. The Centers for Disease Control and Prevention (CDC) estimates that there are approximately 20 million new cases of reportable STIs annually in the United States, half of which occur in people aged 15–24 years old. When STIs spread to the reproductive organs, they can be associated with severe morbidity and loss of fertility.
Because males and females have different urogenital anatomy, urogenital infections may affect males and females differently. In this chapter, we will discuss the various microbes that cause urogenital disease and the factors that contribute to their pathogenicity.
- 23.1: Anatomy and Normal Microbiota of the Urogenital Tract
- The urinary system is responsible for filtering the blood, excreting wastes, and helping to regulate electrolyte and water balance. The urinary system includes the kidneys, ureters, urinary bladder, and urethra; the bladder and urethra are the most common sites of infection. Common sites of infection in the male reproductive system include the urethra, as well as the testes, prostate and epididymis. The common sites of infection in females are the vulva, vagina, cervix, and fallopian tubes.
- 23.2: Bacterial Infections of the Urinary System
- Urinary tract infections (UTIs) include infections of the urethra, bladder, and kidneys, and are common causes of urethritis, cystitis, pyelonephritis, and glomerulonephritis. Bacteria are the most common causes of UTIs, especially in the urethra and bladder. Bacterial cystitis is commonly caused by fecal bacteria such as E. coli. Pyelonephritis is a serious kidney infection that is often caused by bacteria that travel from infections elsewhere in the urinary tract.
- 23.3: Bacterial Infections of the Reproductive System
- In addition to infections of the urinary tract, bacteria commonly infect the reproductive tract. As with the urinary tract, parts of the reproductive system closest to the external environment are the most likely sites of infection. Often, the same microbes are capable of causing urinary tract and reproductive tract infections. Bacterial vaginosis, Chlamydia, Gonorrhea, and Chancroid are diseases caused by bacteria.
- 23.4: Viral Infections of the Reproductive System
- Genital herpes is usually caused by HSV-2 (although HSV-1 can also be responsible) and may cause the development of infectious, potentially recurrent vesicles. Neonatal herpes can occur in babies born to infected mothers and can cause symptoms that range from relatively mild (more common) to severe. Human papillomaviruses are the most common sexually transmitted viruses and include strains that cause genital warts as well as strains that cause cervical cancer.
- 23.5: Fungal Infections of the Reproductive System
- Candida spp. are typically present in the normal microbiota in the body, including the skin, respiratory tract, gastrointestinal tract, and female urogenital system. Disruptions in the normal vaginal microbiota can lead to an overgrowth of Candida, causing vaginal candidiasis. Vaginal candidiasis can be treated with topical or oral fungicides. Prevention is difficult.
- 23.6: Protozoan Infections of the Reproductive System
- Trichomoniasis is a common STI caused by Trichomonas vaginalis. T. vaginalis is common at low levels in the normal microbiota. Trichomoniasis is often asymptomatic. When symptoms develop, trichomoniasis causes urinary discomfort, irritation, itching, burning, discharge from the penis (in men), and vaginal discharge (in women). Trichomoniasis is treated with the antiflagellate drugs tinidazole and metronidazole.
Thumbnail: Candida blastospores (asexual spores that result from budding) and chlamydospores (resting spores produced through asexual reproduction) are visible in this micrograph. (credit: modification of work by Centers for Disease Control and Prevention).