Microbiology of the GU tract (incomplete) Flashcards
List bacteria causing STI
Chlamydia trachomatis (chlamydia) Neisseria gonorrhoeae (gonorrhoea) Mycoplasma genitalium Treponema pallidum (syphilis)
List virus causing STI
Herpes simplex (genital herpes) Hepatitis and HIV (not covered in this lecture)
List Parasites causing STI
Trichomonas vaginalis
Phthirus pubis (pubic lice or “crabs”)
Scabies (not covered in this lecture)
Reason for a specific bug causing a specific syndrome
Proclivity for one or more tissues
Predictable inflammatory response.
Sonococci that infect the male urethra generally produce an intense neutrophil response that leads to a purulent discharge and pain with urination
C. trachomatis:in the same tissue, more likely to produce a mild, watery discharge or no symptoms at all.
If you are testing for one organism, should you test for other organisms as well?
YES.
Coinfections are common.
STI pathogens move together: gonorrhea and chlamydia cause urethritis; genital ulcers greatly increase the probability of HIV acquisition.
Pre-test probability matters
Which bacterial species is most common in vaginal flora?
Lactobacillus spp. predominate and are protective
- e.g L.crispatusandL. jensenii
Other organisms in vaginal flora
+/- Group B beta-haemolytic Streptococcus - need to be eradicated in pregnant patients
+/- Candida spp. (small numbers)
+/-Strep “viridans” group
Predisposing factors for candida infection
Recent antibiotic therapy
High oestrogen levels (pregnancy, certain types of contraceptives)
Poorly controlled diabetes
Immunocompromised patients
Description of candida
“cottage cheese”
“curdy”
Presentation of candida
intensely itchy white vaginal discharge
Diagnosis of candida
clinical
high vaginal swab for culture
Treatment of candida infection
Topical clotrimazole pessaryor cream, (available OTC)
Oral fluconazole
Non-albicans Candida species
More likely to be azole resistant
Presentation of candida infection in males
Spotty rash of candida balanitis
Less common
Not sexually transmitted
Pathogenesis of gonococcal infection
Incubation period of urethral infection in males - SHORT (2-5 days)
Attaches to host epithelial cells and is endocytosed into the cell to replicate within the host cell and are released into the subepithelial space
Typical urethral infections result in prominent inflammation release of toxic lipo-oligosaccharide and peptidoglycan fragments as well as the release of chemotactic factors that attract neutrophilic leukocytes.
Gram stain features of gonorrhoea
Gram -ve intracellular diploccocus
Neisseria gonorrhoea infects which parts of the body?
urethra
rectum
throat & eyes
endocervix
Which is more common? Gonorrhoea or Chlamydia?
Chlamydia
Morphology of Neisseria gonorrhoea
gram negative diplococcus
Looks like 2 kidney beans facing each other
easily phagocytosed by polymorphs - intracellular appearance on gram film
Other tests for N. Gonorrhoea
Microscopy of urethral/endocervical swabs
- Done in Sexual and Reproductive Health (SRH) clinic – 90+% specificity in males, less in females
Culture on selective agar plates
- Selective agar suppresses growth of normal flora
- Done on endocervical, rectal and throat swabs but NOT high vaginal swabs
- Now only done on patients attending SRH clinic in Tayside
- Swabs from GP patients were often falsely culture negative as organism would die during transit to lab
- Non selective media used where no competing flora are expected (e.g. synovium)
Nucleic Acid Amplification Tests (NAATs)
increase in sensitivity over culture
ability to test urine specimens and self-obtained vaginal swabs,
Inability to perform antimicrobial susceptibility testing
Poor/ inadequately defined positive predictive value of some NAATs when they are used to test low-prevalence populations.
Where the prevalence of N. gonorrhoeae is now well below 1%, the risk of false-positive screening results may be high, and reliable results depend on the use of assays with exquisite specificity.
Will detect dead organisms (have to wait 5 weeks to do “test of cure” tests)
Features of chlamydia trachomatis
Gram non-staining but behaves as gram -ve.
Most common bacterial STI
Obligate intracellular bacteria with biphasic life cycle - “energy parasite”
Does not reproduce outside host cell
Which areas does Chlamydia trachomatis infect?
urethra
rectum
throat and eyes
endocervix
Treatment of chlamydia
Azithomycin (1g oral dose) for uncomplicated chlamidia
Doxycycline 100mg bd x 7 days - this is what is currently stated in guidelines
Which serovars (serological subgrouping) of chlamydia trachomatis causes gential infection?
D-K
Which serological grouping of Chlamydia Trachomatis is identical to Crohn’s disease?
Serovars L1 to L3
Lymphogranuloma Venerum
What treatmet options are available to patients who cannot tolerate azithromycin or doxacyline with chlamydia?
erythromycin
ofloxacin
Diagnosing chlamydia and gonorrhoea
combined NAAT or PCR - tests for both organism in 1 test.
Men: first pas urine sample (not midstream)
Female: HVS or vulvo-vaginal swab (VVS) which can be either self taken or endocervical swab which is clinician taken
Rectal and throat swabs
Eye swabs (babies and adults)
Features of Trichomonas Vaginalis
Single celled protozoal parasite
divides by binary fission (no cyst form is known) – human host only
Transmitted by sexual contact
Clinical features of Trichomonas vaginalis
vaginal discharge and irritation in females
Urethritis in males
How to diagnose T. vaginalis
High vaginal swab
No good test for males
Treatment of T. vaginalis
Oral metronidazole
Describe the discharge of bacterial vaginosis
homegenous
may contain bubbles
Fishy odour
Microscopy of bacterial vaginosis
Adding 10% potassium hydroxide to the discharge on the slide elicits an amine-like, fishy odor, yielding a positive “whiff” test (amines from the anaerobic flora.
A wet mount reveals the absence of bacilli and their replacement with clumps of coccobacilli. Some vaginal epithelial cells are coated with coccobacilli, which may obscure their edges (clue cells) or the normally clear appearance of the cytoplasm. Relatively few polymorphonuclear leukocytes are observed
What is the significance of large numbers of leukocytes in wet mount of BV?
Coincident infection
possibly trichomoniasis or bacterial cervicitis
Consequences of bacterial vaginosis
Increased rate of upper tract infection (endometritis, salpingitis)
premature rupture of the membranes and preterm delivery ( treatment of asymptomatic women with BV who are not at high risk for preterm delivery appears to confer no benefit.)
Women with BV may have increased risk for the acquisition of HIV
4 stages of syphilis infection (incomplete)
- Primary lesion
- Secondary stage
- Latent stage
- Late stage
What is primary lesion stage of syphilis?
Chancre - painless Organisms multiply at inoculation site and gets into bloodstream Extra-genital sites of lesion - 10% Non tender focal lymphadenopathy Heals without treatment
What is secondary stage of syphilis?
Incubation - 6 weeks to 6 months
Large no. of bacteria circulating in the blood
Multiple manifestations at different sites
- “snail track” mouth ulcers
- generalised rash - macular, follicular or pustular rash on palms + soles
- flu-like symptoms
- Lesions of mucous membranes
- Generalised Lymphadenopathy
- Patchy Alopecia
- Condylomata Lata (most highly infectious lesion in syphilis, exudes a serum teeming with treponemes
What is the latent stage of syphilis
No symptoms
low level multiplication of spirochete in the intima of small blood vessels
Some patients will self cure or be treated co-incidentally
What is late stage syphilis
Cardiovascular or neurovascular complications many years later
What are the symptoms of mycoplasma genitalium carriage?
Asymptomatic carriage
List the associated conditions of mycoplasma genitalium
Non gonoccocal urethritis
PID
Presentation of gonorrhea in males
Asymptomatic - <10%
Urethral discharge - >80%
Dysuria
Pharyngeal/rectal infections - mostly asymptomatic
What should be done to manage males having unprotected anal sex?
Offer pre-exposure prophylaxis
Presentations of gonorrhoea in females
Asymptomatic (up to 50%)
Increased/altered vaginal discharge (40%)
Dysuria
Pelvic pain (<5%)
Pharyngeal and rectal infection are usually asymptomatic
Upper genital tract complications of gonorrhoea
Endometritis PID Hydrosalpinx Infertility Ectopic pregnancy Prostatitis
Lower genital tract complications of gonorrhoea
Bartholinitis - inflammation of bartholin gland Tysonitis Periurethral abscess Rectal abscess Epididymitis Urethral stricture
Diagnosing Gonorrhoea
NAATs (screening test) >96% sensitivity
Microscopy (Symptomatic)
- Urethral 90-95% sensitivity
- Endocervical 37-50% sensitivity
Culture (if Micro +ve or contact of GC)
- Urethral >95% sensitivity
- Endocervical 80-92% sensitivity
Treatment of gonorrhoea
First-line: Ceftriaxone 500 mg IM
Second-line: Cefixime 400 mg oral (only if IM injection is contra-indicated or refused by patient)
Test of cure in all patients after 2 weeks
Presentation of primary infection of genital herpes
Blistering and ulceration of the external genitalia Pain External dysuria Vaginal or urethral discharge Local lymphadenopathy Fever and myalgia (prodrome)
What is the incubation period of HSV primary infection?
3-6 days
What is the duration of genital herpes primary infection
14-21 days
Features of reccurent episodes of HSV
More common with HSV-2
often overlooked/misdiagnosed
usually unilateral, small blisters and ulcers
minimal systemic symptoms, resolves within 5-7 days
Investigation and management of genital herpes
Swab base of ulcer (viral medium) for HSV PCR
Give oral antiviral Treatment (Aciclovir 400mg TDS x 5/7)
Consider topical Lidocaine 5% ointment if very painful
Saline bathing
Analgesia
Are HSV-1 attacks more frequent than HSV-2?
YES
When is viral shedding seen most commonly?
More frequent in the first year of infection
More in individuals with frequent recurrences
How do you reduce/manage viral shedding (HSV)?
Acicolvir 700mg BD for 12 months
Special circumstances to take caution with HSV
PREGNANCY
- previous herpes episode means antibodies can be passed to the baby
- First episode in 3rd trimester (within 6 weeks of EDD)
- ? Primary or non-primary
- Inform O+G (review birth plan)
Which HPV genotypes are covered by quadrivalent vaccines?
6, 11, 16, 18
Which HPV genotypes are covered by nanovalent vaccine?
31, 33, 45, 52, 58
Symptoms of HPV vary with gentoype - t or f
TRUE
Clinical sequelae of HPV
latent infection
anogenital warts
palmar and plantar warts
cellular dysplasia/intraepithelial neoplasia
How is HPV transmitted?
Likely to have acquired HPV from asymptomatic partner
Incubation period – 3 weeks to 9 months (3mth)
Subclinical disease is common on all anogenital sites
Transmission of more than one HPV type is common
What to do when patient presents with genital warts?
Cervical screening
Location of anogenital warts of HPV
perianally
sub prepucal
anywhere in the anogenital region
sites of friction
Description of warts in HPV
cauliflower lesion
HPV treatment
Podophyllotoxin (Warticon)
Cytotoxic
Not licensed for extra genital warts (but widely used)
Imiquimod (Aldara)
immune modifier
can be used on all Anogenital warts
Cryotherapy
Done in combination with the above
Cytolytic can require repeat sessions at 2 week intervals
Electrocautery
HPV vaccination indication
Vaccinate both men and women
vaccine is given to MSM men, as those having sex with women would be protected if the woman is vaccinated
Is the HPV vaccination successful in reducing cervical cancer?
YES
79% reduction in CIN 1
88% reduction in CIN 2
89% reduction in CIN 3
How is treponema pallidum transmitted?
Sexual contact
Trans-placental/during birth
Blood transfusions
Non-sexual contact – healthcare workers
How to classify acquired syphilis
EARLY INFECTIOUS
- primary
- secondary
- early latent
LATE NON INFECTIOUS
- Late latent
- Tertiary
Incubation period of primary syphylis
9-90 days (mean of 21 days)
Diagnosis of syphilis
Demonstration of Treponema Pallidum
(from lesions or infected lymph nodes)
- Techniques
- Dark Field Microscopy
- PCR (polymerase chain reaction)
Serological Testing
- Detects antibody to pathogenic treponemes
Non treponemal serological tests for syphilis
VDRL (Venereal Disease Research Laboratory)
RPR (Rapid Plasma Reagin)
Treponemal serological tests for syphilis
TPPA (Treponemal Pallidum Particle Agglutination)
ELISA/EIA (Enzyme Immunoassay) SCREENING TEST
INNO-LIA (Line immunoassay)
FTA abs (Fluorescent Treponemal Antibody absorbed)
