Sexually Transmitted infections

Question 1

STI’s the emerging problem:

• Define an STI?
• UK stats?
• Cost to NHS? HIV? others?
• Those at risk?

Answer 1

• Sexual transmitted infection is an illness caused by an infectious microorganisms with a propensity for transfer between humans through sexual contact.
• In the UK STI’s are the leading communicable diseases - >1.5 million attendances at gum clinics.
• Cost burdens to the NHS: 750 mil PA
• HIV: 580 mil PA
• Others 65 mil PA
• Those at greatest risk:
• Young people with high risk sexual lifestyles.
• men who have sex with men (MSM)
• Disadvantaged socio-economic communities.

Question 2

Microorganisms associated with STI: 
Bacteria? (name 3 + disease)
Viruses? (name 4 + disease)
Fungi? name 1 + disease
Parasites? name 1 + disease
Arthropods? name 2 + disease

Answer 2

Bacteria:

• chlamydia trachomatis = non-specific urethritis
• Neisseria gonorrhoae = Gonnorrhoea
• Treponema pallidum = syphilis

Viruses:

• Papillomavirus (HPV) = genital warts
• Herpes simplex = Genital herpes
• Hepatitis B/C = Hepatitis
• HIV = AIDS

Fungi:
- Candida albicans = thrush

Parasites:
- Trichomonas vaginalis = vaginitis

Arthropods:

• Sarcoptes scabies = genital scabies
• Phthirus pubis (crabs) = Pediculosis pubis

Question 3

Incidence of STI is increasing:

- Why?

Answer 3

Incidence of STI is rising because:
- Modern lifestyles: Multiple partners, pregnancy (morning after pill), internet chat rooms, Geolocation apps (grindr, tinder)

• Drugs and alcohol use.
• MSM - multiple partner exchange
  - Risky sexual practice
• Contraceptive pill
• Lack of education and awareness.

Question 4

Chlamydia trachomatis:

• Transmission?
• Clinical manifestation?
• Complications?
• The national chlamydia screening program?
• Treatment?

Answer 4

Transmission:

• Via vaginal, anal and oral sex.
• Transmitted from mother to baby.
• incubation 1- 3 weeks.

Clinical manifestation:

• Frequently asymptomatic (the silent epidemic)
  - 75% female/ 50% men: reservoir of infection.
  
  • Males: Urethritis (watery, mucoid discharge)
• Females: urethritis, cervicitis, vaginitis.

Complications:

• Pelvic inflammatory disease (PID) 40%
• Infertility in males and females.
• ocular infections in neonates and adults.

The national chlamydia screening program:

• Established 2003
• Aids in detection/treatment of asymptomatic carriers.
• Target group: people >25 who are sexual active (~1:10 pos but asymptomatic)
• location: contraceptive services, abortion clinics, etc.
• 2003-2015 5.5 million tests

Treatment:

• Azithromycin single dose (macrolide)
• doxycycline 7-14 days (tetracycline)

Question 5

Human papillomavirus (HPV):

• how many types and how many are sexual transmitted? main 4 types?
• Transmission?
• Clinical manifestation?
• Treatment?
• Prevention?

Answer 5

• > 100 types of HPV only 30 are sexually transmitted. Main 4 are: 6, 11, 18, 16.

Transmission:

• Via vaginal, anal and oral sex.
• incubation: 1-6 months
• Prevalence greatest (17-33 years)

Clinical manifestation:

• Warts (90% = types HPV 6/11) multiple, dry, keratinized, cauliflower in appearance painless.
• Neoplasia (cancer) Neoplasm conversion (eg cervical cancer) HPV 16/18 - high risk.

Treatment:

• Genital warts: - Podophyllin (cytotoxic)
  - Imiquimod (immunostimulant)
• Cervical/intraurethral : co2 laser removal.

Prevention:

• Vaccination (year 8 secondary school)
• Gardasil (HPV 6, 11, 16, 18) (NHS 2012)
• both boys and girls are now vaccinated. approx age 13.
• New vaccine covers 9 types.
• practice safe sex!

Question 6

Herpes simplex virus:

• How many types?
• Transmission?
• Clinical manifestation?
• Reactivation?
• Treatment?

Answer 6

• Two types of herpes simplex virus:
  
  • HSV type 1 = 40% (predominately oral)
  • HSV type 2 = 60% (predominately genital.

Transmission:
- Vaginal, anal or oral.

Clinical manifestation:

• Primary infection
  - Asymptomatic in 70% of cases
  - Symptoms and be constitutional (generally unwell) or localized
  - untreated attack lasts approx 28 days: latency.

Reactivation:

• tenderness, pain, burning at site of eruption lasting 2 hours to 2 days.
• women: lesions on the labia and perineum
• Men: lesions on shaft, prepuce, glans
• Lesions heal in 7-10 days. Dissemination can lead to encephalitis.

Treatment:

• Acyclovir 5 tablets daily for 1 week
• Famciclovir TDS for 1 week
• Safe sex.

Question 7

Gonorrhoea:

• Microorganism and characteristics?
• Transmission?
• Epidemiology?
• Clinical manifestation?

Answer 7

Microorganism: Neisseria gonorrhoeae

• Gram negative diplococci
• intracellular survival
• Strict human pathogen

Transmission:

• Vaginal, anal or oral sex
• Incubation 2-7 days
• Transmission rates following single exposure: males 20%, females 80%.

Epidemiology:

• Rate higher in urban areas
• Men form 70% of the diagnosis, MSM and blakc ethnic groups account for 1/3 of these.
• females 16-19: males 20-24 years

Clinical manifestation:

• Asymptomatic in many cases 70% females 30& males.
• Males : Urethritis, Dsyuria (pain on urination) Thick, purulent discharge.
• Females: dsyuria, cervicitis, thick purulent discharge.
• Rectal infection: anal discharge, pain on anal sex.
• Throat infection: tonsillitis, purulent discharge.

Question 8

Gonorrhoea: continued

• Complications?
• Pathogenesis: virulence factors?

Answer 8

Complications:

• Males: epididymitis, prostatitis
• Females: (20%) spread to fallopian tubes (salpingitis), Pelvic inflammatory disease (PID), infertility.
• Opthalmia neonatorum
• 1% DGI: bloodstream infection, fever sepsis, arthritis, skin lesions.

Pathogenesis:

• Adherence and endocytosis:
  - Pili (nonciliated columnar epithelial cells)
  - OpA proteins (opacity protein) and LOS
  (lipooligosaccharide)
  - Por proteins (parasite directed endocytosis)

Avoidance of host defence:

• Capsule (sialic acid) Molecular mimicry
• IgA protease (cleaves IgA which is commonly found in

Toxins and damage:
- TP1 and TP2 = Transferrin binding receptors
- LBP2 = Lactose binding receptors.
These proteins receptors remove iron carrying molecules from blood.

Question 9

• Sample collection? Males and females? Transport?
• Non-culture techniques?
• Culture?
• Identification?
• Treatment and prevention?

Answer 9

Sample collection:

• males: ureteral swabs
• Females: Multiple samples: ureteral/endocervical, vaginal.
• Other samples depending on patient history: throat, rectal, blood culture.
• Transport media: Stuarts

Non-culture techniques:

• Direct microscopy of discharge - Presumptive diagnosis if positive: initiate treatment.
• Nuclei acid amplification tests (NAAT): PCR based, rapid, bacteria viability not essential.

Culture:

• Enriched agar: Blood/chocolate agar.
• Selective agar: Modified Thayer-martin/ New York city agar: vancomycin, colistin, nystatin, trimethoprim
• 37 degrees, 48hrs, 5% co2
• Opaque, convex, grey glistening colonies.

Identification:

• Colonies gram negative diplococci
• oxidase positive
• catalase positive
• sugar fermentation (glucose pos, mannose neg, sucrose neg). API
• prolyl aminopeptidase positive (gonocheck)

Treatment and prevention:

• Main strains now resistant to common antibiotics e.g penicillin, ciprofloxacin, tetracycline.
• Guidelines:
  - Ceftriaxone
  - Cefixime
  - azithromycin
• Combination therapy: for drug resistance gonorrohea
  
  • Ceftriaxone
  • azithromycin
• Safe sex : minimize number of sexual partners, use condoms during sex.