STIs ppt

Learning Outcomes

  • Outline the global and UK importance of STIs.
  • Explain the progression of gonorrhoea, chlamydia, and syphilis.
  • Describe the causative bacteria.
  • Explain the commonly used diagnostic tests.
  • Describe the life-cycle of Chlamydia trachomatis.
  • Outline the impact of antimicrobial resistance on prevalence and treatment.

Global Significance of STIs

  • Statistics (WHO):
    • Over 1 million people acquire an STI daily.
    • Approximately 357 million new cases of curable STIs each year including gonorrhoea, chlamydia, syphilis, and trichomoniasis.
    • Over 500 million people live with incurable herpes simplex virus (HSV-2) infections.
    • About 290 million women have an active human papillomavirus (HPV) infection.
  • Demographics:
    • Highest burden in low-income countries.

Classification of STIs

  • By Income Levels:
    • Chlamydia, gonorrhoea, trichomoniasis, and syphilis prevalence vary by economic status of regions:
      • High-income economies: Chlamydia 3.0%, Gonorrhoea 0.3%, Syphilis 0.2%
      • Upper-middle income economies: Chlamydia 6.9%, Gonorrhoea 1.2%, Syphilis 0.3%
      • Lower-middle income economies: Chlamydia 2.4%, Gonorrhoea 0.6%, Syphilis 0.5%
      • Low-income economies: Chlamydia 2.9%, Gonorrhoea 1.1%, Syphilis 1.3%

Vaginal Microbiome

  • Dominant Species:
    • Lactobacillus: major component; regulates vaginal pH by lactic acid production, produces antimicrobial substances.
    • Other bacteria include Proteobacteria, Firmicutes, Actinobacteria, etc.

Antimicrobial Activity in Semen

  • Composed of antibacterial peptides including:
    • Lysozyme
    • Lactoferrin
    • Phospholipase A2
    • Secretory leukocyte protease inhibitor
    • Semenogelin 1-derived peptides

Gonorrhoea

  • Causative Agent: Neisseria gonorrhoeae
  • Infection Characteristics:
    • Commonly affects mucous membranes of the urethra, endocervix, rectum, pharynx, and conjunctiva.
    • Uncomplicated forms are localized. Complications can include disseminated gonorrhoea and septic arthritis.
  • Transmission: Almost always sexually transmitted.
  • Complications:
    • In men: epididymitis, prostatitis, acute lymphangitis
    • In women: often asymptomatic, can lead to pelvic inflammatory disease (PID), complications during pregnancy.

Chlamydia

  • Causative Agent: Chlamydia trachomatis
  • Symptoms: 70% of women and 50% of men are asymptomatic.
  • Complications:
    • PID in women can lead to long-term health effects.
    • In men, complications can involve epididymo-orchitis.
  • Screening: Use of NAATs for diagnosis as it offers high sensitivity and specificity.

Syphilis

  • Causative Agent: Treponema pallidum
  • Stages:
    • Primary: painless ulcer (chancre)
    • Secondary: systemic symptoms including rash and lymphadenopathy.
    • Latent: no symptoms but serological confirmation.
    • Tertiary: rare but serious complications can arise.
  • Transmission: Direct contact with infectious lesions.
  • Risk Factors: Prevalence is increasing in men compared to women.

Antimicrobial Resistance (AMR)

  • AMR plays a critical role in the treatment of gonorrhoea with resistance developing to many antibiotics since initial clinical use in 1935.
  • Surveillance required to track Gonococci resistance patterns over time.

Diagnostic Methods

  • Diagnostic Tests:
    • Gonorrhoea: Diagnosis commonly through NAATs; culture methods track AMR.
    • Chlamydia: Diagnosed through NAATs and has high sensitivity and specificity ratings compared to other tests.
    • Syphilis: Confirmed via serology tests including non-treponemal and treponemal tests.

Conclusion

  • STIs remain a prominent global health issue, with chlamydia, gonorrhoea, and syphilis as major concerns.
  • Understanding the microbiology, transmission mechanisms, and resistance patterns is critical for developing effective prevention and treatment strategies.