Microbial Diseases of the Genitourinary Tract

1. Genitourinary Tract Overview

• Genitourinary tract = Urinary system + Reproductive system

• Infections:

  • Can be local or systemic

  • Routes:

    • Ascending (e.g. via urethra)

    • Local invasion (via skin/mucosa)

  • Females at higher risk: shorter urethra + proximity to anus

2. Normal Microbiome

Urinary Tract Microbiome

• Previously thought sterile; now known to host microbes (mostly in lower tract).

• Females: mainly Lactobacillus spp.

• Males: Lactobacillus, Corynebacterium, Streptococcus, Pseudomonas

• Role unclear: may outcompete pathogens

Vaginal Microbiome

• Dominated by Lactobacillus (esp. L. crispatus, L. iners, etc.)

• Produces lactic acid and H₂O₂ → maintains acidic pH (3.8–4.4)

• Prevents pathogen colonization

3. Urinary Tract Infections (UTIs)

Types

• Urethritis: urethra (often STI-related)

• Cystitis: bladder

• Pyelonephritis: kidneys

• Prostatitis: prostate (men)

Cystitis

• Symptoms: urgency, dysuria (pain), frequency

• More common in women

• Treatment:

  • Trimethoprim (folic acid inhibitor)

  • Nitrofurantoin (affects TCA cycle + DNA/protein synthesis)

Prostatitis

• Pain in pelvis, back, urination/ejaculation issues

• Can cause infertility, fever, urinary retention

• Needs rapid antibiotics

Pyelonephritis

• Often from untreated cystitis

• Caused by E. coli or Proteus mirabilis

• Symptoms: back/groin pain, fever, foul urine, blood/pus in urine

• Treatment: Cefalexin (safe for pregnancy)

4. Uropathogenic E. coli (UPEC)

• Causes >80% of UTIs

• FimH adhesin binds to bladder cells, resists flushing

• Risk factors: sexual activity, menopause, hygiene, spermicide use

• Can cause kidney damage, urosepsis, death (7.8% mortality)

5. Catheter-Associated UTIs (CAUTIs)

• Common pathogens: Proteus mirabilis, E. coli

• P. mirabilis:

  • Swarming motility

  • Urease production → crystalline biofilm

  • Hard to treat even after catheter removal

• Complications: pyelonephritis, sepsis, death

6. Bacterial Vaginosis (BV)

• Cause: microbiome disruption (↓ Lactobacilli, ↑ anaerobes)

• Key pathogen: Gardnerella vaginalis

• Diagnosis (Amsel Criteria): needs 3/4:

  • Fishy smell

  • Thin grey discharge

  • pH > 4.5

  • 20% clue cells

• Risk factors: douching, soaps, IUDs, sex

• Treatment: Metronidazole, Clindamycin

  • 40% recurrence rate

7. Sexually Transmitted Infections (STIs)

Chlamydia (C. trachomatis)

• Most common bacterial STI

• Intracellular; 2 forms:

  • EB (infectious, non-replicating)

  • RB (non-infectious, replicating)

• Often asymptomatic

• Treatment: Doxycycline

• Can cause PID, infertility, neonatal infections

Pelvic Inflammatory Disease (PID)

• Infection spreads to uterus/fallopian tubes/ovaries

• Complications:

  • Scarring → infertility, ectopic pregnancy

  • Sepsis

Gonorrhoea (N. gonorrhoeae)

• Gram-negative diplococcus

• Symptoms: pus discharge, painful urination

• Adhesins for binding mucosa

• Complications: endocarditis, arthritis, meningitis, neonatal blindness

• Treatment: Ceftriaxone

Syphilis (T. pallidum)

• Spirochete; gram-negative (but lacks LPS)

• Infects via mucosa/broken skin

• Stages:

  • Primary: chancre

  • Secondary: rash, systemic

  • Latent

  • Tertiary: nerve/organ damage, dementia

• Treatment: Penicillin (esp. IV for neurosyphilis)

8. Candidiasis (Fungal)

• Candida albicans

• Vaginal thrush – more common in women

• Risk factors: antibiotics, contraceptives, pregnancy, scented products

• Treatment: Fluconazole (inhibits ergosterol)

9. Comparison Table: Chlamydia vs Gonorrhoea vs Syphilis