Understanding Common Sexually Transmitted Infections and UTIs
Urinary Tract Infection (UTI) with Escherichia coli (E. coli)
E. coli is a common cause of UTI.
Risk Factors, Pathogenesis, and Clinical Manifestations
Risk Factors: Female gender, sexual activity, urinary stasis, catheter use, and diabetes.
Pathogenesis:
- Introduction of E. coli (usually from the gastrointestinal tract)
- Colonization of the urethra (via urethral opening)
- Adherence to uroepithelial cells (via fimbriae)
- Invasion of the bladder (Cystitis)
- Inflammation and immune response
- Symptoms of UTI (dysuria, frequency, urgency, pain)
Clinical Manifestations: Increased urinary frequency, suprapubic pain, hematuria, or fever.
Laboratory Diagnosis
- Urine Culture:
- Gold standard for diagnosing UTI.
- Urine sample is cultured on MacConkey agar, where E. coli produces lactose-fermenting pink colonies.
- Growth of >105 CFU/mL of bacteria in the urine is indicative of infection.
- Microscopic Examination:
- A wet mount or Gram stain of the urine sediment is examined.
- Pyuria (presence of white blood cells) is common, indicative of inflammation.
- Bacteriuria (presence of bacteria) confirms infection.
- Hematuria (blood in urine) can also be observed.
- Urinalysis:
- Leukocyte Esterase Test: Detects the presence of WBCs, confirming inflammation.
- Nitrite Test: E. coli reduces nitrates to nitrites, making this test positive.
- pH and Protein: Urine may be slightly acidic with mild proteinuria.
- Microscopic hematuria might be noted due to bladder irritation.
- Antibiotic Sensitivity Testing:
- After identifying the organism, antibiotic susceptibility is tested.
- Common methods include disk diffusion (Kirby-Bauer test) or MIC (Minimum Inhibitory Concentration) determination.
- Additional Tests:
- Blood Cultures: If systemic infection or sepsis is suspected.
- Ultrasound: To check for hydronephrosis or renal involvement.
Treatment
Ciprofloxacin or amoxicillin may be used.
Chlamydia trachomatis Infection
Likely causing nongonococcal urethritis.
Other Manifestations of Chlamydia trachomatis Infection
- Pelvic inflammatory disease (PID)
- Cervicitis
- Epididymitis
- Conjunctivitis
- Reiter’s syndrome (reactive arthritis)
Laboratory Diagnosis
- Microscopy: Detection of inclusion bodies in cells stained with Lugol’s iodine, which are characteristic of Chlamydia trachomatis.
- Nucleic acid amplification tests (NAATs): These are the most sensitive tests for detecting Chlamydia DNA or RNA from urine, urethral, or cervical swabs.
- Culture: The bacteria can be cultured in specialized cell lines, though it is not commonly done due to time and resource constraints.
- Direct fluorescence antibody (DFA): Fluorescent-labeled antibodies can be used to identify the bacteria in specimens.
Primary Syphilis
The probable etiological agent is Treponema pallidum, a spirochete bacterium.
Risk Factors and Pathogenesis
Risk Factors:
- Unprotected sexual contact (especially with multiple or high-risk partners like commercial sex workers)
- Male-to-male sexual contact
- HIV infection, which increases susceptibility
- Lack of condom use
Pathogenesis:
Treponema pallidum enters the body through mucous membranes or broken skin during sexual contact. It then invades the bloodstream and spreads to various organs.
Clinical Manifestations
- Primary syphilis: A painless, indurated ulcer (chancre) at the site of infection, usually genital, anal, or oral. It typically heals spontaneously in 3–6 weeks but leaves the bacteria in the body.
- Enlarged inguinal lymph nodes (due to regional infection).
- Secondary syphilis can follow if untreated, characterized by skin rashes, mucous patches, and systemic involvement.
Laboratory Diagnosis
- VDRL (Venereal Disease Research Laboratory) / RPR (Rapid Plasma Reagin): Reactive test as seen in the case, indicating syphilis infection.
- Dark-field microscopy: Direct visualization of Treponema pallidum from the chancre.
- FTA-ABS (Fluorescent Treponemal Antibody Absorption Test): Confirmatory test to detect specific antibodies against Treponema pallidum.
Treatment and Prophylaxis
Treatment:
- Penicillin G (intramuscular, single dose) is the first-line treatment for all stages of syphilis.
- Alternative antibiotics like doxycycline or azithromycin can be used in penicillin-allergic individuals.
Prophylaxis:
- Safe sexual practices (use of condoms) to reduce transmission.
- Regular screening for sexually active individuals, especially those with multiple partners or high-risk behavior.
- Early treatment of infected individuals to prevent progression and transmission to others.
Gonococcal Urethritis
The probable etiological agent is Neisseria gonorrhoeae, a Gram-negative diplococcus.
Risk Factors and Pathogenesis
Risk Factors:
- Unprotected sexual contact, especially with high-risk partners like commercial sex workers.
- Multiple sexual partners or a history of sexually transmitted infections (STIs).
- Men who have sex with men (MSM).
Pathogenesis:
- Entry via mucous membranes
- Adherence to epithelial cells
- Pili allow attachment to the urethral and genital mucosal surfaces
- Penetration of epithelial cells
- Bacteria invade and enter host cells
- Invasion of submucosal tissues
- Bacteria spread to deeper tissues causing inflammation
- Immune evasion
- Bacteria evade the immune system by varying surface proteins (antigenic variation)
- Localized inflammation
- Leads to symptoms like dysuria, urethral discharge, and pain
- Potential complications
- In men: Epididymitis, prostatitis
- In women: Pelvic inflammatory disease (PID), cervicitis
Clinical Manifestations
- Urethral discharge (typically yellow or green) and dysuria.
- In men, may lead to epididymitis or prostatitis if untreated.
- In women, cervicitis and potential complications like pelvic inflammatory disease (PID).
Laboratory Diagnosis
- Gram stain: Pus cells with intracellular Gram-negative diplococci seen under the microscope.
- Culture: On modified Thayer-Martin medium, which supports the growth of Neisseria gonorrhoeae while inhibiting other organisms. Colonies are small, convex, and translucent.
- NAAT (Nucleic Acid Amplification Test): A highly sensitive method for detecting gonococcal DNA from urine or swabs, often used as a confirmatory test.
Treatment
- Ceftriaxone 250 mg intramuscularly as a single dose
- Azithromycin (or doxycycline) is often co-administered to treat potential chlamydial co-infection.