10. STIs and HIV

what are STIs

• Sexually transmitted infections

• bacteria, viruses, parasites, lice, mites etc.

• passed through contact with susceptible surfaces e.g. mucus membranes, genital fluid, genital discharge, blood to blood etc.

where does information from STIs come from

• data collected every quarter from sexual health clinic attendances

• demographics, testing, positive infections, treatments and health promotion details

where are high rates of STIs seen in

• young people aged 15-24

• gay, bisexual and other men who have sex with men (GBMSM)

• black caribbean ethnicity

risks factors to consider for STIs

• Age

• ethnicity

• sexuality

• geography

• poverty and social exclusion

• recent partner chnage/ concurrent partners

bacterial STIs

• chlamydia

• gonorrhoea

what pathogen causes chlamydia and what is the infectious vector

• caused by chlamydia trachomatis

• exposure to bacteria through infected secretions/discharge

sites of inoculation in chlamydia

• mucus membranes

  • endocervical

  • urethral

  • rectal

  • rectal

  • pharynx

  • conjunctiva

possible spread of chlamydia

• pelvic inflammatory disease

• Fitz-hugh curtis (peri-hepatitis)

• epididymo-orchitis

• proctitis

• sexually acquired reactive arthritis (SARA)

what pathogen causes gonorhhoea and what is the infectious vector

• caused by neisseria gonorrhoea

• exposure to bacteria through infected secretions/ discharge

sites of inoculation of gonorrhoea

• mucus membranes

  • endocervical

  • urethral

  • rectal

  • pharynx

  • conjunctiva

possible spread of gonorrhoea

• local

  • gland infection and abcesses

  • pelvic inflammatory disease

  • epididymo-orchitis

  • proctitis

• reactive

  • SARA

• systemic→ disseminated gonoccocal infection

presentation of bacterial STIs

• discharge from genital tract/rectum

• discomfort, inflammation, bleeding

• pelvic pain, pain on sex, testicular pain

• joint/skin problems

• conjunctivitis

identification of chlamydia

• too small to see with magnification light, difficult to culture

• PCR test

identification of gonorrhoea

• visible under gram stain with light microscope

  • gram negative

• cultured in specific medium and CO₂ rich envrionment

vaginal infections

• trichomonas vaginalis

• bacterial vaginosis

• candida

pathogen and infectious vector of trichomonas vaginalis

• protozoa

• exposure through infected secretions

site of inoculation of trichomonas vaginalis and possible spread

• site of inoculation

  • vaginal epithelium

  • endo-urethral

• spread

  • vaginal cuff

  • infections

  • reported post hysterectomy

  • PID

pathogen and infectious vector associated with bacterial vaginosis

• bacterial vaginosis associated bacteria

• traditionally thought not sexually transmitted

  • alkinisation of vagina promotes growth of BVAB

site of inoculation and possible spread of bacterial vaginosis

• inoculation→ vaginal epithelium

• possible spread

  • linked with PID

  • possible causative agent associated with more severe disease

pathogen and infectious vector for candida

• yeast→ candida albicans, non-albicans species

• commensal

site of inoculation of candida and possible spread

• inoculation

  • vaginal and vulval epithelium

  • sub prepuce

• spread→ local hypersensitivity

presentation of trichomonas vaginalis

• yellow, frothy discharge

• itch

• vaginal soreness

• urethral irritation

presentation of bacterial vaginosis

• thin, white discharge

• odour

presentation of candidiasis

• thick white clumpy discharge

• itch

• vaginal and vulva soreness

identification of vaginal diseases

• trichomonas vaginalis→ visible using wet mount microscopy

• bacterial vaginosis→ vaginal pH>4.5, gram stain with microscope shows

  • reduced lactobacilli, clue cells

• candida→ gram stain with light microscope shows spores and hyphae

viral STIs

• warts

• molluscum contagiousum

• herpes simplex

pathogen and infectious vector for warts

• human papilloma virus types 6 and 11

• skin to skin contact with viral shedding

site of inoculation and possible spread of warts

• inoculation→ genital and perianal epithelium

• spread→ vagina and cervix, endourethral, rectal mucosa

pathogen and infectious vector of molluscum contagiosum

• pox virus

• exposure to infectious lesions, auto-inoculation

site of inoculation and possible spread of molluscum contagiosum

• inoculation→ any skin

• possible spread→ widespread in immunocompromised

pathogen and infectious vector for herpes simplex

• pathogen→ herpes simplex virus types 1 and 2

• exposure to infectious lesions, asymptomatic shedding, autoinoculation

site of inoculation and possible spread of herpes simplex

• inoculation→ any mucus membrane, damaged epithelium

• systemic infection in pregnancy and neonatal period, HSV meningitis/encephalitis

identification of genital warts

• clinical diagnosis

• biopsy if unclear

• HPV typing not commercially available

identification of molluscum

• clinical diagnosis

• biopsy if unclear

identification of herpes

• PCR swab from visible ulcer or broken skin

• serology will show antibody response

blood-borne infections

• syphilis

• HIV

pathogen and infectious vector of syphilis

• bacteria treponema pallidum

• mucus membrane exposure to bacteria via infectious lesions, blood to blood, vertical transmission

site of inoculation and possible spread of syphilis

• primary chancre on mucous membrane, blood to blood, perinatal

• spread

  • secondary syphilis, myriad of symptoms by systemic spread

identification of syphilis

• treponemes visible with dark ground microscope

• difficult to culture

• test from wet skin lesion

• serology looking for direct and indirect treponemal response

identification of HIV

• first line→ 4th generation assay (45 day window)

• point of care test or venous bloods to check for antigen and antibody to the virus (12 week window)

transmission of HIV

• sexual

• sharing needles, injection of drugs

• occupational

• blood products

• vertical

HIV infection and viral replication

• free virus enters CD4 cell through binding and fusion between virus and coreceptor

• HIV RNA released into cell→ synthesised to DNA

• integrated to cell DNA→ transcription and translation

• new viral protein assembled→ budding of free virus

effects of HIV on immune system

• loss of CD4+ cells

• chronically elevated CD8+ cells but poor quality

• early loss of memory T cells weakens recall response to antigens

stages of HIV

1. primary→ 2-6 weeks, nonspecific illness

2. secondary asymptomatic→ can last 5-10 yrs

3. secondary symptomatic→ immune system destruction, symptoms begin to appear

4. late stage/end stage/ AIDS defining→ presence of indicator diseases

aims of treatment of HIV

• prevent further cell destruction to allow immune system recovery

• prevent further formation

• reduce complications from longstanding chronic inflammation