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Overview of STIs

Overview of STIs. Gabriel Schembri. Chlamydia trachomatis. Definition. Chlamydia trachomatis is an obligate intracellular gram negative bacterium recognised as one of the most common sexually transmitted agents in the world. Aetiology. Chlamydia trachomatis Serovars D-K cause STDs

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Overview of STIs

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  1. Overview of STIs Gabriel Schembri

  2. Chlamydia trachomatis

  3. Definition Chlamydia trachomatis is an obligate intracellular gram negative bacterium recognised as one of the most common sexually transmitted agents in the world

  4. Aetiology • Chlamydia trachomatis • Serovars D-K cause STDs • Serovars A-C cause trachoma • Serovar L causes lymphogranuloma venereum (LGV)

  5. Epidemiology • Most prevalent treatable bacterial STI but still second to TV in rank of common STIs • 10% of under-25s screened via the national chlamydia screening programme are testing positive for chlamydia • The highest rates of chlamydia are among females aged 16-24 years and males aged 20-24

  6. Transmission • One episode of SI ~10% for both sexes. Condom reduces the risk by ~40% • 94% clear infection without treatment after 4 years • 2/3 of contacts of chlamydia test positive for the infection

  7. Signs and symptoms • Men • 50% asymptomatic, most of these will have no clinical signs • Dysuria • Discharge (clear/whitish) or ‘threads’ in urine • Meatitis • Epididymitis

  8. Signs and symptoms • Females Asymptomatic in 70%, most of whom will have no physical signs on examination • Deep dypareunia • Pelvic pain +/-PID • Intermenstrual bleeding • Post coital bleeding • Mucopurulent cervicitis • Dysuria

  9. Complications • Epididymitis • PID (?up to 40%) – pain, infertility, ectopic • Bartholinitis +/- abscess • Endometritis – irregular bleeding • Adverse pregnancy outcomes • Neonatal infection • ?cervical neoplasia • Sexually associated reactive arthritis/Reiter’s syndrome • Fitz-Hugh curtis syndrome

  10. Management • General • Explain the condition and provide written material • Screen for other STIs • Contact trace (look 4 weeks back if patient symptomatic, 6 months if asymptomatic) • Advise no SI for 1 week (including oral sex) and until 1 week after partner is treated (if in a relationship)

  11. Management - uncomplicated Azithromycin 1g po stat OR Doxycycline 100mg bd x7 days Alternatives: Ofloxacin 200mg bd x7 days (expensive) Erythromycin 500mg bd x14 days (GI upsets!!!)

  12. Gonorrhoea

  13. Definition Infection with Neisseria gonorrhoeae - Infects columnar epithelium of mucous membranes i.e. endocervix and pelvic organs, urethra, epididymis, prostate, rectum, pharynx, conjunctivae

  14. Infectivity • Almost exclusively sexual • Exceptions :- Conjunctivitis – sexual but also autoinoculation, accidental transfer from affected individuals living in poor hygiene Vertical – ophthalmia neonatorum (40%), rarely neonatal sepsis, abscesses, anogenital infection

  15. Infectivity • After 1 episode of UPSI – 20-80% • Females more susceptible • Condoms can reduce risk by up to 75% • ¼ of cases are attributable to oral sex

  16. Symptoms • Males: • Urethral infection: urethral discharge (80%), dysuria (50%), asymptomatic (10%) • pharyngeal and rectal infection are usually asymptomatic (occasionally anal discharge and pain or sore throat) • Females • asymptomatic in 50% • abnormal vaginal discharge, abdominal pain, dysuria and menstrual abnormalities sometimes occur

  17. Signs • Males • Meatitis/balanitis with mucopurulent or purulent discharge • Epididymo-orchitis • Females • Mucopurulent cervicitis • PID signs • Both sexes • Asymptomatic esp. females • Rectal discharge, pain, tenesmus • Dissemination: pustular/petechial skin rash, arthralgia, septic arthritis

  18. Management • Screen for other STIs • Contact trace as appropriate • Treat for presumed concurrent chlamydia • First line: • Ceftriaxone 250mg IM stat • Cefixime 400mg po stat • (spectinomycin 2g IM stat)

  19. Management • Alternatives/allergy • Ciprofloxacin 500mg po stat • Ofloxacin 400mg po stat • (spectinomycin 2g IM stat) • Pregnancy/breastfeeding • Cefixime, ceftriaxone, spectinomycin and ampicillin can be used • Quinolones must be avoided

  20. Management • Pharyngeal infection • More difficult to eradicate, therefore avoid the less effective spectinomycin and ampicillin regimes • Can use cephalosporins and quinolones as per genital infections • Needs a test of cure (TOC) • Cefixime not in the guidelines but emerging evidence supports its effectiveness

  21. HIV

  22. Family: Retroviridae Genus: Lentivirus Species: HIV 1 and HIV 2

  23. p24 RNA binding proteins, p7, p9 Matrix,p17 Integrase and Protease enzymes

  24. Origin of HIV A: Chimpanzee, the source of HIV-1, lives in Central Africa B: Sooty mangabey, the source of HIV-2, lives in West Africa

  25. A1, A2, A3, A4 F1, F2 HIV-1 subtypes } variation between subtypes ~ 30% } Sub-subtypes: genetic variability ~ 15% QUASISPECIES - variations in a single individual 1% genetic variability

  26. Quasispecies Primary infection Multiple rounds of rapid replication with errors Daughter viruses become genetically distinct (though very closely related) A number of quasispecies exist in equilibrium in a human host (unless there is selection pressure). These are archived in memory cells

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