STIs Flashcards
Transmission
Any form of sexual activity in which no barrier is used and exchange of fluid or contact with mucosal epithelium occurs
Basically anything goes!
Trends in the UK
STDs levels are high - WHY? Risen 60% 1996-2005, steady now at a high level…
Difficult to change behaviour
Absence of vaccines
Recent rise in STIs in single over 50s
‘safe-sex’ less likely to be practiced
Stable since 2011 at around 400-450,000 cases
-rose year on year until very recently- the 2011 figures show a decrease and then stabilisation overall> BUT STILL 420,000 new cases in 2016
Most in YOUR age group!
Most common STIs
Chlamydia 48% Genital warts 14% Gonorrhoea 11% -on the increase Other STIs
Syphilis diagnosis by gender
Low in females (<1000 per year)
Rise in males since 2013 (now ~6000 per year)
Most cases in which age group
16-34
1 in 25 people in this age group
Main organisms
Neisseria gonnorhoea >>> Gonnnorhoea Chlamydia trachomatis >>> chlamydia Treponema pallidum >>> Syphilis HIV virus- elsewhere Genital Herpes - elsewhere Hepatitis B- elsewhere
N. gonorrhoeae (Gonoccus)
Exclusively a fully virulent human pathogen;
-never found as a commensal
Asymptomatic carrier state: mainly females
Acute urethritis
in 95% males
-only ~ 50% women show discharge, dysuria
Ascend to Fallopian tubes
-acute salpingitis, pelvic inflammatory disease
-sterility
Ophthalmia neonatorum – infant blindness
Oral gonnorhea – very rare, but can result from oral sex with infected man
N. gonorrhoeae pathogenesis
Surface pili- pil proteins- attachment (bundle forming pili - attachment)
Opa proteins- aid attachment
Lipo-ologosaccharide: sialylated- complement resistance- host mimicry
to all above points: Phase and antigenic variation contribute to pathogenicity and hinder vaccine development
Por proteins- nucleate actin aiding cell invasion
Possesses IgA protease- aids survival inside host cells
Release into bloodstream disseminates infection to other sites fever, arthiritis (1-3% women, much lower in men), endocarditis
N. gonorrhoeae epidemiology
In 1980s, fear of HIV infection and > condom usage (barrier methods) decreased infection in developed countries
Very recently, no. cases > again due to promiscuity, travel (including sex trade) and use of oral contraceptives over barrier methods
Co-infection of HIV and N. gonorrhoeae increases transmission of HIV by 500% (WHO)
Infection with N. gonorrhoeae also increases likelihood of contracting HIV 5x
Increased more with males than females (more male cases than female cases - partly because easier to diagnose)
Gonorrhoea - diagnosis
Urethral swab
- susceptible to dessication, so transport medium used
- sub-culture on chocolate agar
- sugar fermentation tests–glucose +ve
- oxidase test positive
Gonorrhoea - treatment
Contact tracing- antibiotic prophylaxis of contacts
Historically penicillin and tetracyclines were drugs of choice
Ceftriaxone (IM) and azithromycin (1g orally) recommended first line choice (also kills chlamydia).
Many 3rd world strains are Penicillin and Tetracycline resistant, susceptibility tests must be performed
Gonococcal resistance
A big deal
Especially to tetracycline
Leeds, July 2016
-first cases of Az resistant strains in world
-approx. 20 cases in 2016, worrying in increases… some infections now nearly untreatable
Syphilist
Major venereal disease for at least last 600 years
Originally known as the ‘french disease’ (morbus gallica)
One theory suggests not present in pre-Columbus Europe.
Modern name coined by Italian poem in which boy is punished by god
Treatment with Mercury
Number of syphilis cases
Going up, especially in males
The rash of secondary syph often seen in infants and an indicator of congenital syphilis
Culturing Treponema pallidum
Unculturable in vitro
-must be cultured in presence of epithelial cell layer
