STIs Flashcards
General principles of STIs?
Human to human transmission most of the time
immunity is rare in STIs, reinfection is common and vaccine development has been difficult
co-infections e.g. chlamydia and gonorrhea are common
What is included in a standard STI screen?
NAAT swab for chlamydia and gonorrhoea
blood test for HIV and syphilis
Describe normal vaginal flora?
Lactobacillus species predominate and are protective e.g. L crispatus and L jensenii
acid pH is normal 4-4.5
other organisms that may be present include group B beta haemolytic strep (only important in pregnancy), candida (in small numbers), strep viridans group
Is candida infection classified as an STI?
no
Most candida infections are?
candida albicans
Candida is a type of?
fungal infection
Predisposing factors to candida infection?
recent antibiotic therapy, high oestrogen levels, poorly controlled diabetes, immunocompromised patients
Symptoms of candida infection?
main symptom= vulval itching
other symptoms include increased thick, white vaginal discharge, vulval burning, external dysuria and superficial dyspareunia
What may be seen on exam of someone with candida?
white, curly adherent plaques on the vaginal wall
Diagnosis of candida?
often clinical but can do high vaginal swab for culture
Describe treatment of candida?
treatment is with azoles, topical clotrimazole pessary or cream (available OTC) or oral fluconazole
note that non albicans candida are more likely to be azole resistant
note that topical treatments can interfere with latex in condoms or diaphragms so may need to use other form of contraception for small amount of time
Gonorrhoea is more common in __1___ vs chlamydia more common in ___2__
1) men
2) women
Describe the bacteria that causes gonorrhoea?
gram negative intracellular diplococcus which infects the urethra, endocervix, rectum and pharynx
Gonorrhoea is a ____ organism so doesn’t survive well when not in ideal growth conditions
fastidious
Coinfection with what two STIs is common?
chlamydia and gonorrhoea
Symptoms of gonorrhoea in men and women?
In women GC can cause increased vaginal discharge, dysuria, postcoital or intermenstrual bleeding and lower abdo pain
In men GC can cause anterior urethritis with mucopurulent or purulent urethral discharge and dysuria
Tests for gonorrhoea?
NAATs (nucleic acid amplification tests) are test of choice as has better sensitivity that culture however as GC antimicrobial resistance is high culture on selective media should be performed prior to any treatment being given
in men FVU or urethral swabs and in women VVS or endocervical
MSM may need pharyngeal or rectal
Incubation of gonorrhoea?
incubation of urethral infection in males is usually 2-5 days and in females 2-14 days
males are more likely to pass it on to a female than a female to a male
Treatment of gonorrhoea?
must refer to SRH to test for sensitivities as there are high rates of antibiotic resistance
first line is usually ceftriaxone and may give azithromycin on top of this but need to do selective culture due to high rates of resistance
What is the commonest bacterial STI in the UK?
chlamydia
Where can chlamydia infect?
the urethra, the endocervix, the rectum, pharynx and conjunctiva
Describe asymptomatic individuals in chlamydia?
up to 80% women and 50% men with chlamydia may be asymptomatic
Incubation of chlamydia?
thought to be 7-21 days
Does gram staining work with chlamydia?
no as it doesn’t have a cell wall
Describe chlamydia serovars?
Serovars D-K cause genital infection, A-C eye infection and L1-L3 lymphogranuloma venereum
Symptoms of chlamydia in women and men?
In women usually infects the endocervix but can infect the urethra. Symptoms include increased vaginal discharge, dysuria, post coital or intermenstrual bleeding and lower abdo pain. Exam of cervix may reveal mucopurulent cervicitis or contact bleeding
in men it can cause urethritis with milky discharge and dysuria
Complication of chlamydia? Who does it particularly affect?
HLA B27 individuals
reiters syndrome or reactive arthritis
Tests for chlamydia?
NAATs
get sample in men FVU or urethral swabs and women VVS or endocervical swabs
Treatment of chlamydia?
doxycyline 100 mg bd for 7 days if intolerant azithromycin 1g od day 1 then 500 mg of for 2 days
What is trichomas vaginalis?
a single cell protozoa parasite
Most men with trichomas vaginalis are ____
asymptomatic
Symptoms of trichomas vaginalis in women?
increased purulent vaginal discharge and malodour
discharge is yellow or grey and frothy and profuse
can also cause vulval pruritis, external dysuria and dyspareunia
strawberrycervix
Diagnosis for trichomas vaginalis in women?
high vaginal swab for microscopy
Treatment of trichomas vaginalis in women?
oral metranidazole 2g as single dose or 400 mg x 2 daily for 7 days
Is bacterial vaginosis a STI?
no
What is the most frequent cause of vaginal discharge?
bacterial vaginosis
How does bacterial vaginosis occur?
more of an imbalance of biota vs infection
occurs when normal lactobacilli dominant vaginal flora are replaced by overgrowth of another bacteria
Symptoms of bacterial vaginosis?
increased vaginal discharge with offensive fishy odour, discharge is creamy white homogenous and may be frothy
no visible inflammation should be seen
Should visible inflammation be seen with bacterial vaginosis?
no
Diagnosis of bacterial vaginosis?
most accurate diagnosis is by microscopy but can be clinical if criteria met (raised vaginal pH > 4.5, characteristic discharge and fishy odour on whiff test)
What is bacterial vaginosis treated with?
oral metranidazole
What is the most common cause of genital ulceration worldwide?
genital herpes
How does transmission of genital herpes occur?
genital to genital contact from someone shedding the virus (who may be asymptomatic)
Genital herpes can be due to _____
HSV 1 or HSV2
Describe primary infection with genital herpes?
occurs when never been in contact with HSV 1 or 2 and can result in blistering and ulceration of external genitalia, pain, external dysuria, vaginal or urethral discharge, local lymphadenopathy, fever and myalgia (sometimes prodrome)
lasts 14-21 days
Describe recurrent genital herpes?
due to reactivation and usually only a few ulcers to a small confined area, systemic symptoms are rare, viral shedding can still occurs and the person is infectious
Recurrent herpes is more common with what type?
HSV 2
Diagnosis of genital herpes?
swab in virus transport medium of deroofed blister for PCR
Why is serology IgG not useful in diagnosing genital herpes?
it just tells you if the patient has ever encountered HSV in life not that the current problem is herpes
Primary infection of genital herpes in pregnancy risks _____
neonatal HSV
Management of genital herpes?
primary: oral aciclovir, consider topical lidocaine if very painful, saline bathing and analgesia for primary episode
recurrent: may do episodic antiviral therapy or suppressive treatment if recurrences very frequent
What is the most common viral STI in the UK?
HPV
What types of HPV usually cause anogenital warts?
6 and 11
Describe treatment of HPV?
there are many treatments with a high failure and relapse rate
topical podophyllotoxin, imiquimod, cryotherapy
HPV vaccination for 16,18,11 and 6 (one that covers 5 further types recently released too)
What causes syphilis?
infection with spirochete bacteria treponema pallidum
Describe testing for syphilis and reasons?
syphilis doesn’t gram stain or grow well in artificial culture medium so diagnosis relies on PCR test or
first serological tests to look for antibodies
then take samples from sites that are infected to do PCR and dark field microscopy
What are the 4 stages of syphilis?
primary, secondary, latent, tertiary
Describe primary syphilis?
between 10-90 days (mean 21) a primary chancre (usually painless ulcer) appears at the site of inoculation, these heal within 2-6 weeks and may go unnoticed if in cervix or rectum
Describe secondary syphilis?
between 6-10 weeks after primary chancre get snail track ulcers, red non itchy maculopapular rash that is also on palms and soles of feet, malaise, generalised lymphadenopathy, anterior uveitis, fever, sore throat
THE GREAT IMITATOR
Describe latent syphilis?
divided into early latent (< 2 yrs since infection acquired) or late (> 2yrs)
no symptoms but test positive
sexual transmission can only occur in early latency
latent syphilis can persist for years or be life long
at this stage sometimes people are treated coincidentally with penicillin for something else
Describe tertiary syphilis?
within 2-30 yrs
gummatous growths
CVS syphilis: aortitis, aortic regurgitation, aneurysm, coronary artery stenosis
neurosyphilis: meningovascular damage and endarteritis of small vessels of brain and spinal cord causing “general paralysis of insane”
What test can be used to monitor syphilis response to therapy?
RPR serological test
Treatment of syphilis?
long acting penicillin injections
all other treatments are inferior and if someone has a penicillin allergy they need desensitised
What is PID?
when infections ascend from the cervix or vagina into the upper genital tract
Who is PID most common in?
young sexually active women
Presentation of PID?
symptoms usually occur in the first part of the menstrual cycle: bilateral abod pain most common, increased discharge, irregular bleeding, deep dyspareunia, dysuria
most common signs= lower abo tenderness and adnexal and cervical motion tenderness
Sequalae of PID?
tubal infertility, increased risk of ectopic pregnancy and chronic pelvic pain
Is a test of cure required after treatment for chlamydia?
no not usually
Is a test of cure required after treatment for gonorrhoea?
yes, need follow up and test of cure because of high resistance rates
Antibiotic treatment of PID?
- Outpatient treatment for 14 days: ofloxacin + metronidazole
- Inpatient treatment: IV ceftriaxone + IV metronidazole + PO doxycycline, review antibiotics daily and follow IV to oral switch criteria, step down to oral doxycycline + metronidazole to complete 14 days
Describe the 2 types of swab and what they are used for?
- Charcoal swabs are for microscopy, culture and sensitivity – can test for BV, gonorrhoea, candida, TV and GBS as well as any other bacterial infection
- NAAT swabs check directly for DNA or RNA of an organism and are specifically for testing for chlamydia or gonorrhoea or mycoplasma genitalium
- When gonorrhoea is found on a NAAT then need to do a charcoal swab for microscopy, culture and sensitivity as there is a high rate of antibiotic resistance
Explain what argyll robertston pupil is?
Argyll Robertson pupil (can be caused by neurosyphilis, Lymes, neurosarcoidosis, diabetes, MS and herpes zoster) – this is a constricted pupil that accommodates when focusing on near objects but does not react to light
