Lecture 17 - Sexually Transmitted Infections Flashcards
What are the most common symptoms of an STI?
no symptoms a genital rash urethral discharge genital ulceration lymph node swelling in groin region raised core body temperature
What is the most prominent STI in the uk?
chlamydia
What are important drivers of STIs?
cognitive
behavioural
biological factors
Cognitive development affecting STI?
younger adults tend to have less life experience so have reduced reasoning or judgement capacity
they tend to be more concrete thinkers so focussed on immediate circumstances and have reduced ability to plan ahead
Behaviour that can affect chances of getting an STI?
less likely to use a condom
more likely to have multiple/overlapping partners
greater likelihood ob substance use
an older partner predisposes to a relationship power imbalance
(sexual negotiation is more difficult, increased risk of involuntary intercourse and unsafe sex)
Why are younger females more susceptible to STIs?
cervical ectopy
decreased local immunity in genital tract
a smaller introitus and/or lack of lubrication can lead to traumatic sex
Increased susceptibility of STI in males?
occurs in uncircumcised males regardless of age
phimosis (foreskin cannot retract over the head of the penis)
Sexual health inequalities?
disproportionately affects those experiencing poverty and social exclusion
Sexual health inequalities are most prevalent in?
asylum seekers and refugees
sex workers and clients
homeless and young people in care
men who have sex with men
some black and minority ethnic groups
young people
What is sensitivity?
the proportion of people with a disease who will have a positive result
What is specificity?
the proportion of people without the disease who will have a negative result
What is high sensitivity good for?
ruling out a disease if a person tests negative
What is high specificity good for?
ruling in a disease if a person tests positive
What is the positive predicted value?
the proportion of people with a positive result who actually have the disease
What is the negative predicted value?
the proportion of people with a negative test who do not have the disease
What is chlamydia trachomatis?
an obligate intracellular parasite
small gram negative bacilli with no peptidoglycan layer in cell wall
What are primarily associated with urogenital infections?
Serovars D-K
vertical transmission between mother and baby possible
What are associated with lymphogranulosum venereum?
Serovars L1, L2, L2a, L3
How does C trachomatis exist?
in two forms
elementary body (infective form)
reticulate body (non-infectious form)
Where do C trachomatis elementary bodies infect?
columnar epithelial cells
incubation period until symptoms is 1-3 weeks
What % of people with C trachomatis are asymptomatic?
50% of infected females
80% of infected males
What might infection with C trachomatis cause?
a mucopurulent cervicitis in females and urethritis in males
What can ascending infection with C trachomatic cause?
pelvic inflammatory disease (PID) in women
5-10% of PID women develop perihepatitis (Fitz-Hugh-Curtis syndrome)
epididymitis in men
What can untreated C trachomatis lead to in women?
10-40% will develop PID
What are the symptoms of PID?
vaginal discharge
lower abdominal pain (dull, aching, crampy, bilateral and constant) worsened by motion, exercise or intercourse
What can PID cause?
increase in risk of infertility, ectopic pregnancy and chronic pelvic pain
What can untreated C trachomatis cause in men?
epididymitis which may result fertility or sterility
prostatitis
urethritis causing painful urination and possible kidney problems
Swabs taken for chlamydia diagnosis?
urethral swab, rectal swab, cervical swab, midstream urine
Tests for diagnosis of chlamydia?
McCoy, Hep 2 or HeLa cell lines treated with cycloheximide (50-85% sensitivity, 100% specificity)
nucleic acid amplification test (85-95% sensitivity, 99-100% specificity)
Treatment for chlamydia patients?
prefer a single dose of treatment
until 2018 was 1g single oral dose of azithromycin
Why have guidelines for treating chlamydia changed?
in response to mycoplasma genitalium co-infection (3-15% of cases)
concomitant rectal infections in woman with urogenital infection, not related to anal intercourse
Treatment of uncomplicated urogenital infection?
doxycycline 100mg bd for 7 days (contraindicated in pregnancy)
azithromycin 1g orally as a single dose, followed by 500mg once daily for two days
Alternative treatment options for urogenital infection?
erythromycin 500mg BD for 10-14 days
ofloxacin 200mg BD (or 400mg OD) for 7 days (CI in pregnancy)
Treatment for LGV?
doxycycline 100mg BD for 21 days
What other advice for treatment of chlamydia?
abstain from all forms of sex during treatment
contact tracing to minimise transmission
Why is doxycycline CI in pregnancy?
it has an ability to concentration in the bone structures in babies
Vaccine for chlamydia?
nasally adminstered vaccine has been developed using a novel fusion protein antigen that covers multiple chlamydia serovars
Administration of the chlamydia vaccine?
3 x IM followed by 2x instranasal boosters
vaginal antibody responses - humoral immunity
interferon gamma production - cell mediated immunity
What is neisseria gonorrhoeae?
a gram negative intracellular aerobic diplococcus
Female to male transmission of neisseria gonorrhoeae?
~20% per vaginal intercourse (60-80% after 4 exposures)
Most common presentation of neisseria gonorrhoeae in males?
mucopurulent urethritis >80%
50% dysuria
Male to female transmission of neisseria gonorrhoeae?
~50-70% after vaginal intercourse
includes vaginal discharge <50%, dysuria (10%), dyspareunia and mild abdominal pain (<25%)
Rectal infections of neisseria gonorrhoeae?
~40% female (similar in MSM)
Pharyngeal infections of neisseria gonorrhoeae?
~15%
oral sex - fellatio > cunnilngus
Incubation period of neisseria gonorrhoeae?
1-14 days
Primary diagnosis of neisseria gonorrhoeae?
by NAAT
sensitivity >96%, specificity 99-100%
What else can be used to diagnose neisseria gonorrhoeae?
culture swabs for diagnosis and/or resistance profiling on Thayer-Martin plates
sensitivity 90-95% for males and 50-75% for females, specificity 100%
Treatment of uncomplicated anogenital and pharyngeal infections of neisseria gonorrhoeae?
1g ceftriaxone IM as a single dose (if susceptibility unknown)
500mg ciprofloxacin as a single dose (if susceptibility known)
Advice for neisseria gonorrhoeae infection?
test of cure in all patients recommended
abstain from all forms of sex for 7 days
Alternative regimes for neisseria gonorrhoeae?
cefixime 400mg orally as a single dose plus azithromycin 2g orally
gentamicin 240mg IM as a single dose plus azithromycin 2g orally
spectinomycin 2g IM as a single dose plus azithromycin 2g orally
azithromycin 2g as a single oral dose
When is cefixime advisable?
if an IM injection is contraindicated or refused by the patient
resistance to cefixime is low in the UK
When is spectinomycin not recommended?
for pharyngeal infection because of poor efficacy
Azithromycin use?
the clinical efficacy does not always correlate with in vitro susceptibility testing and resistance is high
What is anogenital warts (condyloma) caused by?
human papilloma virus (HPV)
around 30 associated with anogenital infections
What are >90% of anogenital warts caused by?
HPV 6 & 11
these types have low oncogenicity
How is HPV spread?
by skin to skin contact (penetrate sex not a prerequisite) or indirect e.g. sex toys
Where is HPV present?
on genitals
groin region
anus
prevalence of HPV?
30-50% of the population
Transmission rates of anogenital warts?
Male to female 55%
female to male 70%
@ 3 months
Incubation period of HPV?
months to years
What vaccine is HPV included in?
the quadrivalent cervix vaccine gardicyl
Treatment of anogenital warts?
restricted to external visible warts
Treatment if <4cm skin surface involved?
podophyllotoxin
Treatment cycles of anogenital warts?
four treatment cycles consist of BD application for 3 days then followed by 4 days rest (highly irritave)
Response rate of treatment of anogenital warts?
30-70% response rate at 4-6 weeks but recurrence is common
What is used for refractory cases?
imiquimod 3x a week for up to 16 weeks
recurrence is less common
What does imiquimod do?
stimulates the immune system to increase uptake of interferine alpha 2 which has potent antiviral activities
Treatment for large surface areas?
cryotherapy or electrocautery to the skin area
cryotherapy is preferred as it has a lower tendency to leave any scarring
What causes anogenital herpes?
HSV 1 or 2
Transmission of HSV?
skin to skin contact (penetrative sex not required) or indirect e.g. sex toys
What % of people infected with HSV will have mild/no symptoms?
80%
What % of the population have HSV 1?
50% by age 30
What % of the population have HSV 2?
3-10% (up to 25% of sexually active persons)
Incubation period of HSV?
4-14 days or even longer
Characterisation of primary infection of HSV?
flu-like symptoms and small blisters that burst to leave red open sores (up to 20 days duration)
Where can these blisters affect?
genitals, rectum, cervix, buttocks or thighs
urination can be painful
Diagnosis of HSV?
by sampling blister (PCR)
Treatment of HSV 1&2?
400mg aciclovir for 5 days
Recurrence of HSV1 ?
50% chance of at least one recurrence
Recurrence of HSV2?
80% chance of at least once recurrence
What diminishes with time of HSV?
frequency and severity
