Microbiology of the GU Tract Flashcards
What are the most common bacterial, sexually transmitted infections?
Chlamydia (Chlamydia trachomatis)
Gonorrhoea (Neisseria gonorrhoeae)
Syphilis (Treponema pallidum)
Name 3 common viral STIs?
Human papilloma virus (genital warts)
Herpes simplex (genital herpes)
Hepatitis and HIV (not covered in this lecture)
What parasitic STIs are the most common?
Trichomonas vaginalis
Phthirus pubis (pubic lice or “crabs”)
Scabies
Why is pubic lice becoming less common?
shaving pubic hair is more common in today’s society
Describe how gonorrhoea and chlamydia can infect the same tissue but cause different symptoms
Gonococci in male urethra produce intense neutrophil response => pus discharge and dysuria
chlamydia in male urethra = produce a mild, watery discharge or no symptoms at all.
Immunity does not occur in the GU tract. TRUE/FALSE?
TRUE
- reinfection is very common
=> vaccine development is very difficult
What species predominates in normal vaginal flora?
Lactobacillus spp. predominate in the “healthy” vagina
What do the lactobacilli in the normal vaginal flora produce?
Lactic acid
+/- hydrogen peroxide
these suppress growth of pathogenic bacteria
What microbes can be found colonising the vagina in small traces?
Candida (just colonising - not causing symptoms)
Strep viridans
Group B Beta Haemolytic Strep
In what group of patients should you treat Group B Beta - haemolytic strep colonisation in the vagina?
Pregnant women (as this can cause complications when child is born)
Describe the discharge found in bacterial vaginosis
- may contain bubbles
- sometimes has a “fish-like” odour
How does a bacterial vaginosis appear on microscopy and what other test an be done?
- “clue cells”- coccobacilli osbcuring edge of vaginal epithelium
- large no.s of leukocytes may indicate coincident infection
- Positive “whiff” test - Add 10% potassium hydroxide to discharge to elicit a fishy odour
What does bacterial vaginosis put women at a higher risk of developing?
- increased rate of upper urinary tract infection (endometritis, salpingitis)
- premature rupture of the membranes and preterm delivery
- increased HIV risk
What STI is the most common in the UK?
Chlamydia
Where can chlamydia affect?
urethra, rectum, throat and eyes (♂ + ♀)
endocervix (♀)
Is chlamydia a gram positive or negative organism?
NEITHER
there is no peptidoglycan in its cell wall => it does not take up Gm stain well
What are the 3 serovar groups of chlamydia and what does each cause?
Serovars A-C = Trachoma - eye infection
Serovars D-K = Genital infection
Serovars L1-L3 = Lymphogranuloma venereum (LGV)
What investigation is used to diagnose gonorrhoea or chlamydia?
- Nucleic Acid Amplification Tests (NAATs) OR PCR
- Male patients – first pass urine sample
- Female patients – High/ vulvo-vaginal swab (can be self-taken by patient)
- Rectal/ throat/ eye swabs can also be self taken if req’d
What are the advantages of NAATs over culture?
- more sensitive (especially if organism has died on way to lab)
- can test urine specimens/self-obtained swabs
- faster (hours VS days)
What are the disadvantages of NAATs over culture?
- more expensive
- may be false positives for gonorrhoea
- doesn’t give antibiotic sensitivity for organism
What types of antibiotic are any strains of gonorrhoea now resistant to in the UK?
- penicillins
- tetracyclines
- quinolones (ciprofloxacin/ofloxacin)
- most oral cephalosporins
Guidance on how to treat gonorrhoea changes very frequently. How is it currently being treated in the UK (2019)?
IM Cetriaxone
What are the 4 stages of Syphilis infection?
- Primary lesion - (chancre)
- Secondary stage - (large nos. bacteria circulating in blood causing manifestations at different sites)
- Latent stage – (no symptoms, but low-level multiplication of spirochaete in small blood vessels)
- Late stage syphilis – cardiovascular or neurovascular complications
What non-specific serological tests can be used in diagnosing syphilis?
VDRL(Venereal Diseases Research Laboratory)
RPR (Rapid Plasma Reagin)
TPPA
What else are the non-specific serological syphilis tests used for?
- monitoring response to therapy
When may non-specific serologial testing for syphilis be falsely positive?
- The tests indicate tissue inflammation
=> may be falsely positive if pt has lupus, malaria, pregnant etc
What virus causes Genital Herpes?
Herpes simplex virus type 1
How is genital herpes spread?
Transmitted by close contact with someone shedding the virus
=> genital/genital contact
=> oropharyngeal/genital contact
Explain the appearance of an acute phase of genital herpes
painful multiple small vesicles
which are easily deroofed
What does it mean that the herpes simplx virus causing genital warts is “latent”?
Virus can reactivate from sacral root ganglion
=> causing recurrent genital herpes attacks
What type of sample and diagnostic test is completed for suspected genital HSV?
Viral swab of deroofed blister for PCR
What anti-viral treatment an be given for Genital Herpes?
Aciclovir
+/- Pain relief
What symptoms does the parasite trichomonas vaginalis cause in males and females?
- vaginal discharge and irritation in females
- urethritis in males
What test is used to diagnose Trichomonas Vaginalis?
High vaginal swab for microscopy
(PCR test also available NOT in Tayside)
=> so no good test for males!
How is trichomonas vaginalis treated?
Oral metronidazole
How is pubic lice transmitted?
- close genital skin contact
Describe the symptoms of pubic lice
Lice bite skin and feed on blood
=> causes itching in pubic area
Female louse lays eggs on hair next to skin => replication
What treatment is used for pubic lice
malathion lotion
What pH is the normal vaginal flora?
4-4.5 (acidic)
How does candida albicans appear on microscopy?
- “budding” Yeasts and hyphae
What are the predisposing factors to candida infection?
- Recent antibiotic therapy
- High oestrogen levels (pregnancy, certain contraceptives)
- Poorly controlled diabetes
- Immunocompromised patients
A girl being treated for a candida infection should prompt her partner to also get treated. TRUE/FALSE?
- NOT an STI
=> partner doesnt need treatment unless they also have candida infection
Describe the appearance of a candida infection on a female’s speculum examination
“cottage cheese” appearance
What treatments may NOT be as effective for Non-albicans Candida species?
More likely to be -azole resistant (clotrimazole/fluconazole)
How does a candida infection appear in males?
Typical “spotty”rash
- Candida Balanitis
- LESS COMMON
Describe how neisseria gonorrhoea appears with gram stain?
Gram Negative intracellular diplococci
Looks like 2 kidney beans facing each other
Why is gonorrhoea only cultured if patients present to the sexual health clinic rather than the GP?
Organism would die in transit to the lab
AND need specific agar to culture
Why do you have to wait before testing patients for cured gonorrhoea infection?
NAAT test can still pick up dead organisms up to 5 weeks after
WHat is the treatment for chlamydia?
NEW GUIDANCE 2019 = Doxycycline 100mg bd x 7 days
Previously was Azithromycin (1g single oral dose) for uncomplicated chlamydia
What shape is the syphilis organism and what tests are used for diagnosis?
- Spirochaete
- Does NOT stain with gram stain and cant be cultured
=> PCR test or serological (blood) tests to detect antibodies
The presence of what antibody indicates an acute syphilis infection?
IgM
What is the best treatment for syphilis?
- Injectable long-acting penicillin
- provided patient is not penicillin hypersensitive)
