Microbiology - genital tract infection Flashcards
What vaccinations are available for STIs?
Hepatitis B, hep A and HPV all available for MSM
What is pre exposure prophylaxis and what are some examples?
Medicine taken before exposure to STI to reduce risk of infection
Tenofovir disoproxil/ emtricitabine
Reduces HIV incidence by 86%
What is post exposure prophylaxis and in what STIs can it be used?
Medicine taken after exposure to reduce risk of infection
Hep B - HPV vaccine up to 7 days
HIV - 3 anti-retrovirals, start within 72 hours for 28 days in total
What are the most common bacterial STIs?
Chlamydia trachomatis, neisseria gonorrhoea and treponema pallidum (syphilis)
What are the most common viral STIs?
HPV (genital warts), HSV (genial herpes), hepatitis and HIV
What are the most common parasitic STIs?
Trichomonas vaginalis, phthirus pubis (pubic lice/crabs), scabies
What are some predisposing factors for candida infection?
Recent antibiotic therapy, high oestrogen levels, poorly controlled diabetes, immunocompromised patients
How does candida present?
Intensely itchy white vaginal discharge
How is candida diagnosed?
Clinical diagnosis
High vaginal swab for culture - majority of cases are caused by C.albicans
How is candida treated?
Topical clotrimazole
Oral fluconazole
What are the symptoms of acute bacterial prostatitis?
Symptoms of UTI but may have lower abdominal pain/back/perineal/penile pain and tender prostate on examination
What causes acute bacterial prostatitis?
Rare complication of UTI
Same organisms as UTI (chlamydia, gonorrhoea, E.coli, enterococcus)
How is acute bacterial prostatitis diagnosed?
Clinical signs + MSSU for C&S (mid stream sample of urine for culture and sensitivity)
How is acute bacterial prostatitis treated?
Ciprofloxacin for 28 days, trimethoprim if high C.diff risk
What organisms are present in the normal vaginal flora?
Lactobacillus species predominates and produces lactic acid which suppresses the growth of other bacteria
+/- strep viridans, GBBHS, candida
What causes bacterial vaginosis?
Replacement of normal flora with gardnerella vaginalis causing the pH to elevate and become more basic (from the normal 4-4.5)
How is BV diagnosed?
Discharge may contain bubbles
Adding 10% KOH to the discharge elicits a fishy odour - positive whiff test
A wet mount reveals the absence of bacilli and their replacement with clumps of coccobacilli (clue cells)
How is BV treated?
Directed against the anaerobic flora - metronidazole for 7 days
BV relapse rate is about 30%
Where can chlamydia trachomatis infect?
Urethra, rectum, throat and eyes + endocervix in women
What kind of bacteria is chlamydia trachomatis?
Obligate intracellular bacteria with biphasic life cycle
Does NOT stain with gram stain - no peptidoglycan wall
What serological group of chlamydia causes a genital infection?
Serovars D-K
What serological group of chlamydia causes lymphogranuloma venereum?
Serovars L1-L3
How is chlamydia trachomatis treated?
Azithromycin PO 1g for uncomplicated chlamydia
Doxycycline 100mg BD for 7 days for complicated chlamydia
How are chlamydia and gonorrhoea diagnosed?
Combined NAATs or PCR - tests for both organisms
Highly sensitive and specific
Men - first pass urine sample
Women - HVS or VVS
Where can neisseria gonorrhoea infect?
Urethra, rectum, throat and eyes + endocervix in women
What kind of bacteria is neisseria gonorrohoea?
Gram negative diplococcus (2 kidney beans)
Much less common than chlamydia infection
Other than NAAT and PCR how can N.gonorrhoea be tested for?
Microscopy of urethral/endocervical swabs
Culture on selective agar plates
What is the treatment for N.gonorrhoea?
IM ceftriaxone
Test of cure is recommended for all patients
What causes syphilis?
Treponema pallidum - does NOT stain with gram stain
How is syphilis diagnosed?
PCR or serological test to detect antibodies
Syphilis is a 4 stage illness, describe the first and last stage?
First stage = primary lesion - chancre
Last stage = late stage syphilis - CVS + CNS complications many years later
What are some non-specific serological tests for syphilis?
VDRL (venereal diseases research lab)
RPR (rapid plasma reagin)
Indicate tissue inflammation, useful for monitoring response to therapy
What are some specific serological tests for syphilis?
TPPA + TPHA
IgM + IgG ELISA - screening test for syphilis
How is syphilis treated?
Very sensitive to penicillin
Injectable long acting preparations of penicillin
What causes genital herpes?
HSV 1 + 2
What kind of virus is HSV?
Enveloped virus containing double stranded DNA
Describe the pathogenesis of genital herpes
Primary infection may be asymptomatic
Virus replicates in dermis and epidermis, gets into nerve endings and causes inflammation -> exquisitely painful multiple small vesicles
Virus can reactivate from the sacral root ganglion causing recurrent herpes attacks
How is genital herpes diagnosed?
Swab in virus transport medium of deroofed blister for PCR test
How is genital herpes treated?
Aciclovir helpful if taken early enough
What kind of organism is trichomonas vaginalis?
Single celled protozoal parasite transmitted via sexual contact
What does infection with trichomonas vaginalis cause?
Vaginal discharge and irritation
How is trichomonas vaginalis diagnosed?
HVS for microscopy
How is trichomonas vaginalis treated?
PO metronidazole
Describe the pathogenesis of pubic lice infection
Acquired from close genital contact
Lice bite skin and feed on blood, which causes itching
Female lice lay eggs on hair next to skin
How are pubic lice treated?
Malathion lotion
