STI's Flashcards
What is a STI?
An illness caused by an infectious microorganism with a propensity (ease) to transfer between humans through sexual contact (vaginal, oral, anal, sex toys)
True or False: STI’s are a major problem worldwide
True!
True or False: In the UK, STIs, are the greatest communicable disease problem
True
•>1.5 million attendances at genitourinary medicine (GUM) clinic
What is the cost burden of STI’s to the NHS?
£750 million / annum
What is the cost burden of HIV and other STI’s to the NHS?
- HIV: £580 million
- Others (gonorrhoea, herpes, syphilis etc): £65 million
STI’s are associated with high morbidity and mortality; they disproportionately affect which groups?
- Young people with high risk (unprotected) sexual lifestyles
- Men who have sex with men (MSM)
- Disadvantaged socio-economic communities (poor educational awareness or resources)
Microorganisms associated with common STI:
Chlamydia trachomatis
Non -specific urethritis
Chlamydia trachomatis does not have a fully formed cell wall- difficult to grow
No. of new cases of non-specific urethritis in the UK (2018)
218,095
Microorganisms associated with common STI: Neisseria gonorrhoae
How many new cases in the UK (2018)?
Gonorrhoea
56,259
Microorganisms associated with common STI: Treponema pallidum
How many new cases in the UK (2018)?
Syphilis
7,541
Microorganisms associated with common STI: Papillomavirus
How many new cases in the UK (2018)?
Genital warts
57,259
Microorganisms associated with common STI: Herpes simplex
How many new cases in the UK (2018)?
Oral and genital herpes
33,867
Microorganisms associated with common STI: Hepatitis B/C
How many new cases in the UK (2018)?
Hepatitis
5 Million
Microorganisms associated with common STI: HIV
How many new cases in the UK (2018)?
AIDS
4,484 (43% MSM)
Microorganisms associated with common STI: Candida albicans
How many new cases in the UK (2018)?
Thrush
80,000
Microorganisms associated with common STI’s: Trichomonas Vaginalis (parasite)
How many new cases in the UK (2018)?
Vaginitis
8,000
Microorganisms associated with common STI: Sarcoptes scabei (arthropod)
Genital scaies
Microorganisms associated with common STI: Phthirus pubis (arthropod-crab louse)
Pediculosis pubis
Incidence of STI is increasing:
How can our modern way of life contribute?
(a) Multiple partners; more promiscuous
(b) Pregnancy – morning after pill
(c) Internet chat rooms; geo-location apps (Blendr / Grindr) allow people to readily contact each other
Incidence of STI is increasing:
Name some important factors
- Drugs / alcohol (mind altering chemicals)
- MSM
- multiple partner exchange
- ‘risky’ sexual practices
- Contraceptive pill (potentially discourages the use of protective barriers such as condoms)
- Lack of education / awareness about STI’s
STI’s on the rise - and in the press
Common themes in headlines:
- Alcohol
- Young people
- MSM
- Lack of awareness of contraception
Which microorganism causes chalmydia?
Chlamydia trachomatis
Does not have a fully developed cell wall so difficult to stain
How is chlamydia transmitted?
- Via vaginal, anal and oral sex
- Transmitted vertically from mother to baby at birth
- Incubation: 1-3 weeks
Describe the clincal manifestations of chlamydia
•Frequently asymptomatic (the silent epidemic):
75% women / 50% men; reservoirs of infection that don’t know they have chlamydia
- Male: urethritis (watery, mucoid discharge)
- Female: urethritis / cervicitis / vaginitis
What are some of the complications associated with chlamydia?
(a) Pelvic Inflammatory Disease (PID) also called salpingitis: 40%
(b) Infertility in male (lowers sperm count) and female
(c) Ocular infection (conjunctivitis): neonates / adults
What is the NCSP?
When was it established?
What is its aim?
The National Chlamydia Screening Programme (NCSP)
- Established in 2003: Control and prevention programme
- AIM: detection and treatment of asymptomatic carriers in uni’s GP’s etc
What is the target group of the NCSP?
What locations are there?
How may tests were carried out 2003-2012?
How many silent infections were diagnosed?
- TARGET GROUP: people < 25 who are sexually active (approx 1:10 POSITIVE but asymptomatic)
- LOCATION: Contraceptive services; abortion clinics; GP surgeries; community pharmacies; outreach clinics; non-health settings
2003- 2012: 5.5 million tests carried out
Of that 5.5 million, 370,000 ‘silent infection’ diagnosed (approx. 7%)
How is chlamydia treated?
- Azithromycin (belongs to macrolides so targets protein synthesis) (Clamelle): single dose; 2 x 500mg
- Doxycycline (Vibramycin): 7-14 days; 200mg
Chlamydia positivity by venue type and sex
What STI does the human papillomavirus cause?
Genital warts
- 100 types
- (antigenic types 6, 11, 16, 18 account for over 70% of infections)
How is HPV transmitted?
- Via vaginal, anal and oral sex
- Incubation: 1-6 months; years
- Prevalence greatest (17-33 YOA)
What are the clinical manifestations of HPV?
•Warts (90% caused by HPV antigenic types 6 /11); multiple, dry, keratinised, ‘cauliflower’ in appearance; painless
NEOPLASIA (CANCER)
•Neoplastic conversion (eg. can cause cervical cancer if you are not vaccinated): HPV antigenic types 16 / 18- high risk
Show the number of HPV-induced cancers (worldwide)
100% of cervical cancer cases are caused by HPV
Mouth, vagina and throat cancer is also significantly associated
How is HPV treated?
•Genital (surfcae) warts
- Podophyllin (cytotoxic)
- Imiquimod (immunostimulatory)
•Cervical /(deeper) intraurethral – CO2 laser removal
How can HPV be prevented?
Prevention:
•Vaccination ( during year 8, secondary school)
- Quadrivalent vaccine Gardasil® ( effective against HPV antigens 6, 11, 16, 18) (NHS, 2012)
- Girls: 2009
- Boys: 2019
Given in 2-3 shots
Long period of activity (up to 10 years)
•Safe sex
What STI does the herpes simplex virus cause?
Herpes
Can be herpes simplex type 1 (traditionally caused oral herpes) and 2 (traditionally cased genital herpes)
(HSV1 -40%; HSV2 -60%)
What are the clinical manifestations of herpes (reactivation)?
•Tenderness, pain, and burning at the site of eruption
lasting 2 hours to 2 days
- Women: Lesions on the labia and perineum
- Men: Lesions on the shaft, prepuce, glans.
•Lesions heal in 7-10 days; dissemination, encephalitis
Virus resides in your nerve cells and reactivates when you are ill/ immunocompromised
How is herpes transmitted?
•Via vaginal, anal and oral sex
Incubation period of 3-7 days
What are the clinical manifestations of herpes (primary infection)?
- Asymptomatic in 70% cases
- Symptoms: constitutional and localised
- Untreated attack lasts approx 28 days; latency
How is herpes treated?
- Acyclovir (Zovirax): 200mg, 5 x daily for 1 week
- Famciclovir (Famvir): 200-250mg, 3 x daily for 1 week
There is no cure
Describe Neisseria gonorrhoeae
- GRAM NEGATIVE DIPLOCOCCUS;
- intracellular survival
- strict human pathogen
How can herpes be prevented?
By safe sex
What microorganism causes gonorrhoea?
Neisseria gonorrhoeae
How is Neisseria gonorrhoeae transmitted?
•Via vaginal, anal and oral sex
Affinity for non-ciliated columnar epithelial cell
- Incubation period: 2-7 days
- Transmission rates following single exposure:
male-20%; female-80%
Females more likely to become more infected because the male ejaculate may contain Neisseria gonorrhoea
•Mother to baby transmission
Describe the epidemiology of gonorrhoea?
- Rates higher in urban regions esp. London
- Men form 70% of the diagnoses; MSM and black ethnic groups account for 1/3 of these
- Female16-19 years; male 20-24 years
What percentage of asymptomatic cases of gonorrhoea are there?
•Gonorrhoea is asymptomatic in many cases
- 70% female
- 10% male
What are the clinical manifestations of gonorrhoea in males?
(a) Urethritis (urethral inflammation)
(b) Dysuria (pain on urination)
(c) Thick, purulent penile discharge
What are the clinical manifestations of gonorrhoea in females?
(a) Dysuria
(b) Cervicitis (inflammation of the cervix)
(c) Thick, purulent (sometimes bloody) vaginal discharge
- Rectal infection: anal discharge, pain on anal sex
- Throat infection: tonsillitis; purulent exudate
What are the complications of gonorrhoea in males?
Epididymitis, prostatitis
What are the complications of gonorrhoea in males?
(b) Females (20%): spread to fallopian tubes (salpingitis); pelvic inflammatory disease (PID); infertility
- Opthalmia neonatorum
- 1% Disseminated gonococcal infection (DGI) DGI: bloodstream infection –fever, sepsis, arthritis, skin lesions
Pathogenesis: Virulence Factors
Stage 1: Adherence and endocytosis
(a) Pili (good at attaching to non-ciliated columnar epithelial cells)
(b) Opa (opacity) proteins and LOS (lipooligosaccharide) which also helps the organism to attach
(c) Por (porin) proteins (parasite directed endocytosis) allow organism to become internalised into human cells
Pathogenesis: Virulence Factors
Stage 2: Adherence and endocytosis
(a) Capsule (organism surrounds itself with our own sialic acid, this is molecular mimicry.)
(b) IgA protease (against the most abundant antibody within the urogenital system, IgA)
Pathogenesis: Virulence Factors
Stage 3: Adherence and endocytosis
(a) transferrin binding proteins- Tbp1 , Tbp2
(b) lactoferrin binding protein- Lbp 1
Laboratory diagnosis of gonococcal infection: Sample collection
(A)Sample collection
- Males: urethral swab (3cm insertion and rotation)
- Females: multiple samples; urethral / endocervical / vaginal
- Other samples depending upon patient history / clinical presentation : throat / rectal / blood cultures
- Transport medium eg. Stuart’s
- Direct examination and culture of clinical samples in GUM clinic preferred
Laboratory diagnosis of gonococcal infection: Non- culture techniques
•Direct microscopy of discharge (see lots of white blood cells with lots of gram negative diplococci within them)
Presumptive diagnosis if positive; initiate treatment
Nucleic acid amplification tests (NAAT)
Amplify the bacterial antigen on the swab or in the urine
PCR-based: Rapid; detects / amplifies specific DNA; bacterial viability not essential
Laboratory diagnosis of gonococcal infection: Culture techniques
- ENRICHED agar: Blood / chocolate agar
- SELECTIVE agar: Modified Thayer-Martin / New York City agar; vancomycin, colistin, nystatin, trimethoprim
- 37oC / 48h / 5% CO2
- Opaque, convex, grey, glistening colonies, 2mm
Laboratory diagnosis of gonococcal infection: Identification and confirmation of N. gonorrhoeae isolated by culture
- Colonies: Gram-negative diplococci
- Oxidase + (organism contains cytochrome oxidase C
- Catalase + (breaks down H2o2 into H2O and O2
- CHO fermentation (glucose+, maltose-, sucrose-); API
- Prolyl aminopeptidase + (red coloration)
(Gonochek II, commercially available)
How is gonococcal infection treated/
•Many strains now resistant to common antibiotics eg. penicillin (18%), ciprofloxacin (quinolone) (22%), tetracycline (48%)
British National Formulary Guidelines:
(a) ceftriaxone (250mg; IM; single injection)
(b) cefixime (400mg; oral; single dose)
(c) azithromycin (2g single dose)
2013: Combination therapy for DRNG
NICE Guidelines for treatment of uncomplicated gonorrhoea (2017)
- 500mg ceftriaxone (single dose, injected into the muscle) AND
- 1g azithromycin (single dose, orally)
Describe the main method of preventing of gonococcal infection
Safe sex
(a) Minimise number of sexual partners
(b) Use condoms during mouth-to-penis sex, vaginal and anal intercourse
2017: ETX-0914 (Zoliflodacin, phase 3)
Describe
Key points: STI
- STI are caused by numerous microorganisms; associated risk factors
- Top 5 acute STIs are chlamydia, genital warts, herpes, gonorrhoea and syphilis
- N. gonorrhoeae possesses a variety of virulence factors
- Clinical spectrum of gonorrhoea: asymptomatic – symptomatic; associated with complications
- Laboratory diagnosis is essential to confirm the identity of the causative agent and determine antimicrobial sensitivity
- Combination therapy needed for DRNG
- Prevention is better than cure!
Why is Neisseria gonorrhoea becoming resistant to azithromycin?
N. Gonorrhoea may be exposed to sub-lethal levels of azithromycin intended for the treatment of chlamydia
