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
Transmission of syphilis: Treponema pallidum
Sexual contact via minute skin abrasions
Vertical transmission- cross placental: Congenital syphilis
Syphilis progression
Initial contact –> 2-10 weeks (primary chancre - blister) –> primary syphilis (enlarged inguinal nodes, spontaneous healing) –> 1-3 months –> secondary syphilis (flu-like myalgia, headache, fever; mucocutaenous rash; spontaneous resolution) –> 2-6 weeks –> latent syphilis –> 3-10 years –> tertiary syphilis (neurosyphilis; general paralysis of the insane; tabes dorsalis; CV syphilis; aortic lesions; heart failure; progressive destructive disease)
Syphilis: still a major health problem globally
Major WHO program in 1950s and 60s almost eradicated endemic syphilis- now on rise
6 million new cases estimated yearly by WHO
-co-infection with HIV common
-hinders treatment
Increases infectivity and spread of HIV
Congenital syphilis
Transmitted cross-placenta
-can lead to still-birth
-congenital infection
-birth deformities, silent infection – presents as facial and tooth deformities at 2 years of age
‘Millenium Development Goals’ call for 60% reduction in mortality among under-fives by 2015.
In some developing countries 50% of stillbirths might be attributable to syphilis
WHO estimate 200,000 deaths of baby/ fetus
Prevention and cure of (congenital) syphilis
Cheap-effective testing kits are now available
A trial in Haiti with decentralised screening and antibiotic treatment reduced cases by 75% in 2 years.
Syphilis: identified as a winnable battle
Progress good…but missed 2015!
-Current focus is elimination of mother-to-child transmission of HIV AND Syphilis- success in some countries- Cuba…
Chlamydia trachomatis
Most common STI in the UK
» 115,000 new cases in 2009 (out of 383,000 STIs in total)
-often asymptomatic in females
-50% symptomatic in males
-re-infection common as immunity weak
Incubation period 7 – 14 days
Disease due to direct damage to cells and immunopathology causing fibrosis and scarring
-can also cause conjunctivitis- common co-occurence.
Chlamydia - serotypes
A-C: Trachoma- eye infections in 3rd world
D-K: Non-specific urethritis, cervicitis, proctitis, conjunctivitis, PID
L1-3: LGV-severe venereal disease, tropical countries
Trachoma
Biggest cause of preventable blindness in world
Conjunctivitis and trachoma
Common cause of conjunctivitis Also in neonates- infection in birth Major cause of blindness worldwide -with 6 million cases of blindness due to trachoma -not STI in true sense
Chlamydia infection in men
Asymptomatic infection ~ 50% Non specific urethritis Strong associations with: -acute epididymitis -prostatitis -male infertility
Chlamydia infection in women
Asymptomatic infection ~ 70 %
Mucopurulent cervicitis
Urethral infection
Pelvic inflammatory disease in up to 40% - ascending infection involving uterus, fallopian tubes, and other pelvic structures
Complications include chronic pelvic pain, ectopic pregnancy and infertility
Other diseases associated with chlamydia
Proctitis – especially homosexual men Reactive arthritis (mainly men) – acute onset urethritis, genital swelling. Involves mostly knees, ankles, toes. -also called Reiter’s syndrome Neonates infected during birth ~ 20% conjunctivitis and/or pneumonia
Chlamydia: small but deadly
Very small obligate intracellular parasite
Small genome
Enters through minute abrasions
Specialised life-cycle#Seems to avoid and not stimulate immune responses (privileged site?)
Seems to avoid and not stimulate immune responses (privileged site?)
Chlamydia: restricted cell range
Prefers to infect non-ciliated columnar and cubiodal epithelium: genital tract from urethra up to fallopian tubes and rectum
Also respiratory and conjunctival cells
Chlamydia: what to do if you are infected
Tests are available on NHS: 1. Culture in cells 2. Direct immunofluorescence and ELISA 3. PCR tests (known as NAAT) TREATMENT: Azithromycin (single dose). Doxycycline (longer course)
