Microbial Diseases of the Urinary and Genital Systems – Key Vocabulary

Structure and Function of the Urinary System

• Organs
  • Two kidneys, two ureters, one urinary bladder, one urethra
• Innate protective mechanisms
  • Valves that block back-flow from bladder → kidneys
  • Acidic urine (pH < 6) inhibits many microbes
  • Mechanical flushing during urination

Structure and Function of the Genital Systems

• Female
  • Two ovaries, two uterine (fallopian) tubes, uterus (with cervix), vagina, external genitals (vulva)
• Male
  • Two testes
  • Duct system: epididymis → ductus (vas) deferens → ejaculatory duct → urethra
  • Accessory glands + penis

Normal Microbiota of the Urinary & Genital Tracts

• Urine is normally low in microbes but not sterile
• Vagina
  • Dominated by Lactobacilli that secrete H2O2 and lactic acid; numbers ↑ with estrogen
  • Additional residents: streptococci, anaerobes, gram-negatives, Candida albicans (yeast)
• Male urethra & semen
  • Urethra delivers bacteria into semen
  • Seminal vesicle flora: Propionibacterium, Prevotella, Lactobacillus

Bacterial Diseases of the Urinary System

• Terminology
  • Urethritis → inflammation of urethra
  • Cystitis → urinary-bladder inflammation
  • Ureteritis → infection of ureters
  • Pyelonephritis → kidney inflammation (one or both)

Cystitis

• Etiology: usually Escherichia coli
• Clinical
  • Dysuria (painful/difficult urination)
  • Pyuria (pus) ± hematuria
• Therapy: nitrofurantoin or fluoroquinolone

Pyelonephritis

• 75\% of cases: E. coli
• Sx: fever, back/flank pain; often bacteremia
• Pathology: scarring → potential renal failure
• Lab Dx
  • >100,000 CFU ml^{-1} of single species
  • Positive leukocyte-esterase (LE)
  • Urinalysis: pyuria, hematuria, proteinuria, nitrituria
• Virulence: P-fimbriae aid ascension to kidney
• Rx: 2nd/3rd-generation cephalosporin

Leptospirosis

• Agent: Leptospira interrogans (spirochaete, stains poorly, obligate aerobe)
• Reservoir: urine of domestic & wild animals
• Transmission: skin/mucosal contact with contaminated water
• Manifestations
  • Fever, headache, myalgia
  • Weil’s disease → renal failure
  • Pulmonary hemorrhagic syndrome
• Dx: rapid serologic test
• Rx: doxycycline

Sexually Transmitted Infections (STIs) — General

• Often asymptomatic; (>30) distinct infectious agents
• Barrier condoms largely preventive

Gonorrhea

• Pathogen: Neisseria gonorrhoeae (Gram-negative diplococcus)
• Sites: genital, pharyngeal, anal
• Pathogenesis
  • Fimbriae attach to columnar epithelial mucosa → invasion between cells → inflammation + purulent exudate
• Clinical
  • Men: painful urination, purulent discharge, epididymitis
  • Women: few/no symptoms; risk of pelvic inflammatory disease (PID)
• Virulence factors: fimbriae, Opa proteins, IgA protease; high antigenic variability → poor adaptive immunity
• Dx: Gram stain, culture, NAATs
• Rx: ceftriaxone (current CDC first-line)

Nongonococcal Urethritis (NGU) / Nonspecific Urethritis (NSU)

• Any urethritis not due to N. gonorrhoeae
• Common agents: Chlamydia trachomatis, Mycoplasma genitalium
• Sx: painful urination, watery discharge; frequently silent; may ascend → PID in women
• Dx: NAATs
• Rx: azithromycin + doxycycline (cover both agents)

Pelvic Inflammatory Disease (PID)

• Extensive infection of female pelvic organs
• Usually polymicrobial: N. gonorrhoeae + C. trachomatis
• Salpingitis (uterine-tube infection) is hallmark complication
• Rx: triple therapy → doxycycline + ceftriaxone + metronidazole (broad anaerobe & atypical coverage)

Lymphogranuloma Venereum (LGV)

• Agent: C. trachomatis (L1–L3 serovars)
• Epidemiology: tropical regions; emerging elsewhere in MSM populations
• Pathogenesis: infects lymphoid tissue → tender inguinal/femoral lymphadenopathy ± genital ulcer
• Dx: NAAT specific for C. trachomatis
• Rx: doxycycline
• Chlamydial biology: obligate intracellular; lacks ATP production; two forms
  • Elementary body (infectious)
  • Reticulate body (replicative)

Syphilis

• Agent: Treponema pallidum (Gram-negative spirochete; fastidious, slow-growing)
• Virulence: corkscrew motility enables tissue invasion; antigenic variation
• Epidemiologic note: U.S. incidence rising since 2001
• Disease stages
  1. Primary: hard chancre at inoculation site; organisms enter blood & lymph
  2. Secondary: systemic maculopapular rash (palms/soles) + mucous-patch lesions
  3. Latent: asymptomatic (early vs late)
  4. Tertiary (years later): immune-mediated gummas, cardiovascular syphilis, neurosyphilis
  • Congenital syphilis: placental transfer → fetal demise or neurologic injury

Genital Herpes

• Virus: Herpes simplex virus 2 (HSV-2)
• Presentation: clusters of painful vesicles on genitalia; dysuria; heal ~2 weeks
• Latency: virus travels retrograde to sacral sensory ganglia; reactivation triggered by stress, menses, illness → anterograde spread → recurrent lesions & asymptomatic viral shedding
• Virulence: infected cell protein (ICP); envelope glycoproteins (gB, gC, gD, etc.)
• Neonatal herpes
  • Transplacental (rare) → spontaneous abortion / severe anomalies (40 % survival)
  • Most perinatal via exposure to birth canal
  • Dx: PCR; Rx: IV acyclovir

Genital Warts (Condylomata Acuminata)

• Pathogen: Human papillomavirus (HPV)
• Types
  • HPV 6 & 11 → visible warts
  • HPV 16 & 18 (noted as 7 & 9 in slide) → cervical, anal, oropharyngeal cancers
• Oncoproteins E6 & E7 inactivate p53 and Rb tumor suppressors
• Tx: wart removal, podofilox, imiquimod
• Prevention: 9-valent HPV vaccine (covers 6, 11, 16, 18 + 5 others)

Bacterial Vaginosis (BV)

• Etiology: Gardnerella vaginalis (pleomorphic Gram-variable rod)
• Trigger: loss of protective Lactobacillus → vaginal pH > 4.5
• Sx: gray/white thin discharge with fishy odor
• Microscopy: "clue cells" (epithelial cells coated w/ bacteria)
• Virulence: biofilm formation; vaginolysin (pore-forming toxin)
• Dx: Amsel criteria or NAAT
• Rx: metronidazole

Candidiasis (Vulvovaginal)

• Agent: Candida albicans (yeast)
• Predisposing factors: antibiotics, diabetes, high estrogen (pregnancy, contraceptives)
• Sx: thick cottage-cheese discharge, minimal odor, pruritus
• Dx: microscopy (pseudohyphae) or culture
• Rx: clotrimazole (topical) or fluconazole (oral)

Trichomoniasis

• Protozoan: Trichomonas vaginalis (flagellate; normal low-level resident)
• Virulence: surface lipoglycans (TvLGs) & cysteine proteinases degrade host tissues & immune factors
• Grows when vaginal acidity disturbed
• Sx: irritation, profuse thin greenish-yellow discharge with strong odor
• Dx: wet mount motile trophozoites, DNA probe, or NAAT
• Rx: metronidazole (patient & partner)

Cross-Topic Connections & Implications

• Normal flora balance (Lactobacilli) crucial for vaginal health; disruptions predispose to BV, candidiasis, trichomoniasis.
• Many urogenital pathogens (N. gonorrhoeae, C. trachomatis, G. vaginalis) form biofilms → chronicity, antibiotic tolerance.
• Antigenic variation (N. gonorrhoeae, T. pallidum, HSV) hinders vaccine development & long-lasting immunity.
• Public-health relevance
  • Rising syphilis & gonorrhea resistance necessitate updated guidelines (dual therapy, surveillance).
  • HPV vaccination has potential to reduce cervical cancer globally.
• Ethical/Practical dimensions
  • Screening asymptomatic individuals (e.g., NAATs for Chlamydia) prevents silent progression to infertility.
  • Condom promotion & vaccination programs are cost-effective preventive strategies.