Pathogenic Microorganisms of the Urogenital Tract & Sexually Transmitted Diseases (STDs)

Genitourinary Tract: Structure and Defenses

Overview of the Genitourinary Tract

The genitourinary tract consists of two distinct organ systems: the urinary tract and the genital (reproductive) system. The urinary tract is responsible for removing metabolic wastes from the blood, regulating body processes, and forming and transporting urine. The genital system is primarily involved in reproduction.

• Urinary tract components: Kidneys, ureters, bladder, and urethra

• Genital system components: Testes, epididymides, vas deferens, prostate gland, scrotum, penis (male); uterus, fallopian tubes, ovaries, vagina, cervix (female)

Urinary Tract Anatomy

• Kidneys: Filter metabolic wastes from the blood

• Ureters: Tubes that transport urine from kidneys to bladder

• Bladder: Stores urine until excretion

• Urethra: Conducts urine to the exterior; in males, also part of the reproductive tract

Male Reproductive Anatomy

The male reproductive system produces, maintains, and transports sperm and is the source of male sex hormones. The urethra serves as the terminal organ for both urinary and reproductive tracts.

• Testes: Produce sperm and hormones

• Epididymides: Coiled tubes for sperm maturation

• Vas deferens: Transports sperm to the ejaculatory duct

• Prostate gland: Contributes to semen

• Scrotum and penis: External structures housing testes and urethra

Female Reproductive Anatomy

The female reproductive system includes the uterus, fallopian tubes, ovaries, vagina, and cervix. The cervix is a common site of infection and connects the uterus to the vagina.

• Uterus: Site of fetal development

• Fallopian tubes: Transport ova from ovaries to uterus

• Ovaries: Produce ova and hormones

• Vagina: Muscular canal for intercourse and childbirth

• Cervix: Lower part of uterus, opening to vagina

Defenses of the Genitourinary Tract

The genitourinary tract employs several innate defenses to prevent infection:

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

• Desquamation: Shedding of epithelial cells with attached microbes

• Urine properties: Acidic pH, lysozyme (breaks down peptidoglycan), lactoferrin (inhibits bacterial growth), secretory IgA (specific immunity)

• Female reproductive tract: Mucus membranes, secretory IgA, acidic pH (due to bacterial fermentation of glycogen)

• Male reproductive tract: Flushing action of urine

Normal Biota of the Genitourinary Tract

Normal biota play a significant role in the health of the genitourinary tract. The outer urethra harbors nonhemolytic streptococci, staphylococci, corynebacteria, and lactobacilli. The female genital tract, especially the vagina, is colonized by lactobacilli, which maintain an acidic environment, and low levels of Candida albicans.

Urinary Tract Infections (UTIs)

Overview and Types

UTIs are common infections of the urinary tract, often caused by normal biota from the gastrointestinal tract. Types include:

• Cystitis: Infection of the bladder

• Pyelonephritis: Infection of the kidneys

• Urethritis: Infection limited to the urethra

Signs and Symptoms

• Cystitis: Sudden onset pain, frequent urination, dysuria (burning), cloudy or bloody urine, low-grade fever, nausea

• Pyelonephritis: Back pain, high fever, risk of permanent kidney damage

Causative Agents and Epidemiology

• 95% of UTIs are caused by normal GI biota, especially Escherichia coli (80%), Staphylococcus saprophyticus, and Enterococcus

• Catheter-associated UTIs (CA-UTIs) are common in healthcare settings

• Women are more susceptible due to anatomical proximity of urethra to anus

Treatment and Prevention

• Treatment: Sulfa drugs (e.g., trimethoprim-sulfamethoxazole), phenazopyridine for symptom relief, alternative antibiotics for resistant strains

• Prevention: Good hygiene, minimizing catheter use, proper screening

Sexually Transmitted Infections (STIs) of the Genitourinary Tract

Discharge Diseases

Discharge diseases are STIs characterized by increased fluid discharge from the reproductive tract. Major examples include gonorrhea, chlamydia, and trichomoniasis.

Gonorrhea

• Causative agent: Neisseria gonorrhoeae (Gram-negative diplococcus)

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

• Symptoms in females: Urinary and genital tract infection, mucopurulent or bloody discharge, salpingitis, pelvic inflammatory disease (PID), risk of sterility or ectopic pregnancy

• Complications: Dissemination to joints, skin, meningitis, endocarditis; neonatal eye infections

Pathogenesis and Virulence Factors

• Attachment via fimbriae, antigenic and phase variation, IgA protease production, endotoxin release

Diagnosis and Treatment

• Diagnosis: Gram stain (males), ELISA or PCR (females), culture on Thayer-Martin agar

• Treatment: Ceftriaxone plus azithromycin or doxycycline; no vaccine available

Chlamydia

• Causative agent: Chlamydia trachomatis (obligate intracellular bacterium)

• Symptoms in males: Urethritis, discharge, painful urination, epididymitis

• Symptoms in females: Cervicitis, discharge, salpingitis, PID, risk of infertility

• Complications: Lymphogranuloma venereum, neonatal conjunctivitis and pneumonia

Pathogenesis and Diagnosis

• Intracellular growth, immune evasion, inflammation-induced tissue damage

• Diagnosis: PCR, ELISA, direct fluorescent antibody, urine test

Treatment and Prevention

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

• Prevention: Barrier protection, annual screening for at-risk populations

Trichomoniasis

• Causative agent: Trichomonas vaginalis (flagellated protozoan)

• Symptoms: Often asymptomatic; females may have frothy, greenish discharge; increased susceptibility to other infections and pregnancy complications

• Transmission: Sexual contact

Genital Ulcer Diseases

Overview

Genital ulcer diseases are characterized by lesions on the genitals, increasing the risk of HIV infection. Major examples include syphilis, chancroid, and genital herpes.

Syphilis

• Causative agent: Treponema pallidum (spirochete)

• Stages: Primary (chancre), secondary (rash, systemic symptoms), tertiary (gummas, cardiovascular and neurological complications), latent periods

• Congenital syphilis: Transmitted from mother to fetus, causing developmental defects or stillbirth

Diagnosis and Treatment

• Dark-field microscopy, serological tests (FTA-ABS), public health contact tracing

• Penicillin G is the treatment of choice

Chancroid

• Causative agent: Haemophilus ducreyi (pleomorphic gram-negative rod)

• Symptoms: Painful soft chancre, swollen lymph nodes

• Transmission: Sexual contact, associated with poor hygiene

Genital Herpes

• Causative agents: Herpes simplex virus 1 and 2 (HSV-1, HSV-2)

• Symptoms: Painful vesicles, recurrent outbreaks, possible encephalitis, neonatal herpes (high mortality)

• Pathogenesis: Latency in nerve cells, reactivation by stress or other triggers

• Treatment: Acyclovir, valacyclovir; no cure or vaccine yet

Wart Diseases of the Genital Tract

Human Papillomavirus (HPV) Infection

• Causative agent: Human papillomaviruses (nonenveloped DNA viruses)

• Symptoms: Genital warts (condyloma acuminata), risk of cervical, penile, anal, and oropharyngeal cancers

• Transmission: Direct contact, autoinoculation

• Prevention: Gardasil vaccine, Pap smear screening

• Treatment: Wart removal; infection is incurable

Molluscum Contagiosum

• Causative agent: Unclassified virus in the Poxviridae family

• Symptoms: Wartlike growths on genital mucosa or skin

• Transmission: Sexual contact, fomites, autoinoculation

Group B Streptococcus Colonization

Overview

Group B Streptococcus (GBS) colonizes 10–40% of women asymptomatically. Colonization during pregnancy can lead to neonatal infections, including sepsis, meningitis, and pneumonia, as well as maternal complications.

• Screening: Recommended for all pregnant women at 35–37 weeks

• Treatment: Penicillin or ampicillin during labor; erythromycin for resistant strains

Additional info: These notes integrate and expand upon the provided material with academic context, definitions, and examples, and include only images that directly reinforce the adjacent content.