Infectious Diseases Affecting the Genitourinary System

Genitourinary Tract: Anatomy and Defenses

Overview of the Genitourinary Tract

The genitourinary tract consists of two distinct organ systems: the urinary tract and the genital (reproductive) system. Both systems are closely associated anatomically and functionally, and each has unique defenses against infection.

• Urinary tract: Removes metabolic wastes, regulates body processes, forms urine, and transports it out of the body.

• Genital system: Functions mainly in reproduction, with distinct male and female anatomical features.

Urinary Tract Anatomy

• Kidneys: Filter metabolic wastes from the blood.

• Ureters: Tubes that transport urine from the kidneys to the bladder.

• Bladder: Stores urine until excretion.

• Urethra: Conduit for urine to exit the body; in males, also part of the reproductive tract.

Male Reproductive System Anatomy

• Testes: Produce sperm and hormones.

• Epididymides: Coiled tubes for sperm maturation.

• Vas deferens: Transports sperm to the ejaculatory duct.

• Prostate gland: Contributes to semen.

• Penis and scrotum: External organs; the penis houses the urethra.

Female Reproductive System Anatomy

• Uterus: Muscular organ for fetal development.

• Fallopian tubes: Transport ova from ovaries to uterus.

• Ovaries: Produce ova and hormones.

• Vagina: Muscular canal connecting cervix to external body.

• Cervix: Lower part of uterus, common site of infection.

Natural Defenses of the Genitourinary Tract

• Flushing action of urine: Removes microbes from the urinary tract.

• Desquamation: Shedding of epithelial cells with attached microbes.

• Acidic pH: Inhibits microbial growth, especially in the vagina.

• Lysozyme: Enzyme that breaks down bacterial cell walls.

• Lactoferrin: Binds iron, inhibiting bacterial growth.

• Secretory IgA: Provides specific immune protection.

Additional info: The composition of normal biota and the effectiveness of these defenses can vary with age, hormonal status, and anatomical differences between sexes.

Normal Biota of the Genitourinary Tract

Urinary System Biota

• Lower urethra: Contains diverse microbiota; upper tract is less colonized.

• Female urethra: Short and close to anus, increasing UTI risk.

• Penile flora: Aerobic Pseudomonas and Staphylococcus species; anaerobes under foreskin in uncircumcised males.

Female Genital Tract Biota

• Pre-puberty and post-menopause: Biota similar to urethra; pH near neutral.

• Childbearing years: Lactobacillus species dominate, producing acid and lowering pH (4.2–5), which inhibits pathogens.

• Candida albicans: Present at low levels; overgrowth causes yeast infection.

Urinary Tract Infections (UTIs)

Types and Symptoms

• Cystitis: Bladder infection; pain, urgency, dysuria, cloudy urine, hematuria, low-grade fever.

• Pyelonephritis: Kidney infection; back pain, high fever, risk of permanent damage.

• Urethritis: Infection limited to the urethra.

Causative Agents

• 95% caused by normal GI biota.

• Escherichia coli: Responsible for 80% of cases.

• Staphylococcus saprophyticus, Klebsiella pneumoniae, Proteus mirabilis: Other common agents.

Transmission and Epidemiology

• Community-acquired UTIs: Not person-to-person; GI tract to urinary system.

• More common in women due to anatomy.

• Recurrent UTIs: Some E. coli invade deeper tissues and evade antibiotics.

Treatment

• Nitrofurantoin (Macrobid): Commonly used antibiotic.

• Phenazopyridine (Pyridium): Relieves symptoms; colors urine orange/red.

• Many E. coli strains are resistant to penicillins.

Leptospirosis

Overview and Causative Agent

• Zoonosis: Associated with animal urine; affects kidneys, liver, brain, eyes.

• Causative agent: Leptospira interrogans, a spirochete with hooked ends.

Transmission and Treatment

• Contact with contaminated water or soil through skin abrasions or mucous membranes.

• Early treatment with doxycycline, penicillin G, or ceftriaxone is effective.

Sexually Transmitted Infections (STIs) of the Genitourinary Tract

STI Statistics

• Chlamydia: 1.6 million cases (2021, U.S.)

• Gonorrhea: 696,764 cases

• Syphilis: 171,074 cases

• Syphilis among newborns: 2,677 cases

Gonorrhea

• Causative agent: Neisseria gonorrhoeae, a Gram-negative diplococcus.

• Symptoms in males: Urethritis, painful urination, yellowish discharge, possible infertility.

• Symptoms in females: Mucopurulent/bloody discharge, painful urination, risk of pelvic inflammatory disease (PID), infertility, ectopic pregnancy.

• Neonatal risk: Eye infections (ophthalmia neonatorum), blindness; prevented by antibiotic eye drops at birth.

• Virulence factors: Fimbriae for attachment, antigenic variation, IgA protease, endotoxin release.

• Treatment: No vaccine; treat with antibiotics, often combined with Chlamydia treatment due to coinfection risk.

Chlamydia

• Causative agent: Chlamydia trachomatis, an obligate intracellular Gram-negative bacterium.

• Symptoms: Often asymptomatic; males—urethritis, discharge, epididymitis; females—cervicitis, discharge, salpingitis, PID.

• Complications: Lymphogranuloma venereum, neonatal conjunctivitis, and pneumonia.

• Diagnosis: PCR, ELISA, NAATs (gold standard).

• Treatment: Doxycycline or azithromycin; treat all sexual partners; rescreen after 3–4 months.

Vaginitis and Vaginosis

• Vaginitis: Inflammation, itching, burning, discharge; most commonly caused by Candida albicans.

• Vaginosis: Discharge without significant inflammation; often due to Gardnerella species.

• Diagnosis of vaginosis: Presence of clue cells (epithelial cells covered with bacteria).

Genital Ulcer Diseases

• Syphilis: Caused by Treponema pallidum, a spirochete; progresses through primary, secondary, and tertiary stages, with latent periods.

• Primary syphilis: Hard, painless chancre at infection site.

• Secondary syphilis: Systemic symptoms, rash, lymphadenopathy.

• Tertiary syphilis: Cardiovascular and neurological complications, gummas.

• Congenital syphilis: Transmitted from mother to fetus; can cause severe developmental defects.

• Diagnosis: Dark-field microscopy, serology (RPR, immunoassays), NAATs.

• Treatment: Penicillin G is the drug of choice.

Other Ulcer Diseases

• Chancroid: Caused by Haemophilus ducreyi; soft, painful ulcers.

• Genital herpes: Caused by HSV-1 or HSV-2; painful vesicles, recurrent episodes, risk of neonatal herpes.

• Treatment: Acyclovir and derivatives reduce symptoms but do not cure herpes.

Wart Diseases

• Human papillomavirus (HPV): Over 100 types; some cause genital warts, others cause cervical, anal, or oropharyngeal cancers.

• Prevention: Vaccination (covers up to 9 types), barrier protection, regular Pap smears for cervical cancer screening.

• Treatment: Warts can be removed, but infection is incurable.

Other Notable Infections

• Group B Streptococcus: Colonizes 10–40% of women; can cause neonatal sepsis, pneumonia, and meningitis. Screening recommended at 35–37 weeks of pregnancy.

Summary Tables

Major Infectious Diseases of the Genitourinary System

Disease	Causative Agent	Key Symptoms	Transmission	Treatment/Prevention
UTI	E. coli, S. saprophyticus, others	Dysuria, urgency, cloudy urine	Endogenous (GI tract)	Nitrofurantoin, hygiene
Gonorrhea	N. gonorrhoeae	Discharge, PID, infertility	Sexual contact	Antibiotics, condoms
Chlamydia	C. trachomatis	Discharge, PID, conjunctivitis	Sexual, vertical	Doxycycline/azithromycin
Syphilis	T. pallidum	Chancre, rash, gummas	Sexual, vertical	Penicillin G
Genital herpes	HSV-1, HSV-2	Painful vesicles, recurrences	Sexual, vertical	Acyclovir
HPV	HPV types 6, 11, 16, 18, etc.	Warts, cancer risk	Sexual, autoinoculation	Vaccine, Pap smear
Vaginitis	C. albicans	Itching, discharge	Opportunistic, sexual	Azole antifungals
Vaginosis	Gardnerella spp.	Fishy discharge	Endogenous	Metronidazole