Microbiology of GU Tract Flashcards
What are common bacterial causes of STIs? (2)
- Chlamydia Trachomatis
- Neisseria Gonorrhoea
----sidelines: Mycoplasma Genitalium Treponema Pallidum (syphillis)
Viral causes of STIs? (2)
- Genital warts: HPV
- Genital Herpes: HSV
- Hepatitis and HIV
What parasites may cause STI?
- Trichomonas Vaginalis
- Phthirus Pubis (“crabs”/pubic lice)
- Scabies
What is characteristic of Gonococci?
State a clincal symptom.
- huge PUS formation d/t an INTENSE neutrophil response
- pain with urination
How diff. is an infection by C.Trachomatis?
- prodn of a MILD, watery discharge
- or no symptoms at all
What is taken into account for index of the infectiousness of the case ?
- conc. and PHENOTYPE of the organism
- susceptibility of the sexual partner
- resistance of the host (hereditary/acquired or innate)
What should be kept in mind when testing for a specific STI?
- IMMUNITY is RARE
- re-infections are common
- vaccine development is difficult
- THEREFORE check for multiple STI
Which pathological lesion of the GU tract can predispose a person to acquiring HIV ?
- Genital ULCERS
Which 2 STIs contribute to urethritis?
- Gonorrhoea
- Chlamydia
- —coninfections are common so CHECK for ALL
What is the importance of specifically choosing which patients for STI testing?
- ensure from the hx that STI testing is required
- or they are likely to fall in the FALSE positive region
What bacterial spp. is predominant in the normal vaginal flora?
- Lactobacillus spp.
L.Crispatus and L.jesenii
What pH does the normal vaginal flora create and why?
- d.t prodn of LACTIC ACID +/- hydrogen peroxide by the lactibacillus spp.
Apart from the lactiobacillus spp. in the normal vaginal flora, what other organisms are found in the flora?
+/- Group B Beta-hemolytic streptococcus (get rid of in pregnancy)
+/- Candida spp. *small no. is NORMAL
+/- Strep Viridans gr.
Describe the appearance of lactobacillus on epithelial cell on histology.
- Gram Positive bacilli
- purple staining of the rod-shaped bacteria
How does Candida Albican appear on gram film?
- budding
- Yeasts and Hyphae
What are predisposing factors of Candida?
- RECENT antibiotic therapy
- high estrogen levels (pregnancy/ contraceptives)
- poor DM control
- immunocompromised pts ( low CD4 counts and HIV )
How is a candida infections presented as and how to diagnose it?
- INTENSELY itchy w/ WHITE vaginal discharge
- dx by HIGH vaginal swab for culture
How to treat candida vaginal infection?
What specific fungal pathogen is apparently resistant to azoles?
- TOPICAL CLOTRIMAZOLE (pressary/cream)…available as OTC
- Oral FLUCONAZOLE
….non-albicans candida species are more likely to be azole resistant
What is a candidal infection in men called and how does it present as?
- Candida Balantitis
- red spotty rash on penis
- —very uncommon
Describe the pathogenesis of the GC infection…
GC attaches to HOST epithelium cells and is endocytosed within the host cell and released into the sub-epithelium space
What cascade of chemokines is triggered with a typical GC urethral infection?
- prominent inflammation and
- release of lipo-oligosaccharide and peptidoglycan fragments
- release chemotactic factors
- this attracts neutrophils
Why do some gonoccal strains cause asymptomatic genital infection?
- differences in the organism’s ability to bind complement-regulatory proteins that DOWNREGULATE the prodn of chemotactic peptides
Describe the appearance of N.Gonorrhoea with gram stain and under the microscope.
- Gram (-)ve INTRACELLULAR diplococci
- paired PINK spheres in the cell
How common is N.Gonorrhoea and which part of the body does it infect?
- much LESS common than chlamydia
- infects the URETHRA, RECTUM, throat and eyes and endocervix
What is characteristic of the lifeline of N.gonorrhoea?
- it’s a Fastidious organism (dies easily)
- therefore should do molecular tests to check for its presence
How to test for presence of N.Gonorrhoea?
- Microscopy of urethral/ endocervical swabs
- Culture on Selective AGAR plates (for rectal, throat and endocerival swabs)—may come out as false negative
- NAATs- urine specimen and vaginal swabs
What is NAAT?
- Nucleic Acid Amplification Test
- increase in sensitivity
- searches the genetic material of the micro-organism
What is required for the pt to do, after they have done their first NAAT test?
—–pt to come in, in 5 weeks time to do “test for cure” tests
What is the commonest STI in the UK and what areas are commonly affected ?
- chlamydia trachomatis
- urethra, rectum, throat and eyes, endocervix
Why is C.Trachomatis known as an energy parasite?
- it does NOT reproduce OUTSIDE a host cell
- it’s an obligate intracellular bacteria with biphasic life cycle
What serological groupings of chlamydia trachomatis are a/w an STI?
Serovars D-K (genital infection)
Serovars L1-L3 (lymphogranuloma venereum)
Which chlamydial sero group is a/w MSM?
- L1-L3
What is treatment for C.Trachomatis?
- Doxycycline 100mg bd x 7 days
- azithromycin 1g single dose
- erythromycin for 14 days
How is the NAAT test sample obtained from men and women differently?
Men: First pass URINE sample; not mid-stream
Female: High vaginal swab or vuvlo-vaginal swab, or endo cervical (speculum needed tho)
—–for both: rectal, throat and eye swabs
—-vuvlo-vaginal can be SELF-TAKEN
What is the historic mainstay dx of the gonorrhea?
by CULTURE; generally with antibiotic-containing selective media
What are the advantages of NAATs?
- slight increase in sensitivity over culture
- can test urine specimens and vaginal swabs
What is a disadvantage of NAAT?
- can’t perform antimicrobial susceptibility testing
- poor or inadequately defined positive predicitve value of some NAAT when -used to test LOW-prevalence popns
What is the risk of performing NAAT in an area of low prevalence of N.Gonorrhoeae?
- risk of FALSE-POSITIVE screening
What is Trichomonas vaginalis/Bacterial Vaginosis caused by?
- a single celled protozoal parasite
- divides by binary fission (human host)
- transmitted by sexual contact
What does trichmonas vaginalis present as?
- vaginal discharge (frothy and fishy smell)
- vaginal bleeding
- genital burning/itching
How to dx and rx t.vaginalis?
- high vaginal swab for MICROSCOPY (PCR test)
- rx: Oral metronidazole
What will a wet mount reveal for bacterial vaginosis?
- the ABSENCE of lacto-bacilli
- a lot of CLUE cells (as epithelial cells are coated with coccobacili)
Which STI is a.w increased risk of HIV acquisition?
women with Bacterial vaginosis d/t disturbance of microbiology
What is the danger with BV and pregnancy?
- risk of pre-term delivery
- d/t Premature rupture of the membranes
Which STI condition is a.w Upper genito-tract infection?
- Bacterial vaginosis
- —-may cause endometritis and salpingitis
How to treat Bacterial vaginosis?
- directed against the anaerobic flora with metronidazole for 7 days
—-relapse is 30 %
(no benefit from treating male sexual partners)
What is syphilis caused by?
- TREPONEMA PALLIDUM
does not stain gram stain
How is syphilis diagnosed?
- PCR or Serological blood tests
- –can’t be grown in artificial culture media
Can a syphilis test come across as positive despite not having sexual contact?
- yes
- 3 more Treponema Palidum Subspecies that are non-sexually transmitted variants; but can’t be serologically differentiated from one another
- Syphilis; Yaws; Bejel; Pinta
What are the 4 stages of syphilis?
- Primary Lesion (chancre): innoculation site
- Secondary Stage: systemic manifestations
- Latent Stage- no symptoms (spirochaete multiply in t.intima of small blood vessels)
- Late Stage- CVS/ Neurovascular complications years later (DEMENTIA/ TABE DORSALIS/ gait imbalance/GUMMA/AORTIC ANEURYSM and CORONARY ARTERITIS)
What are the manifestations in the secondary stage of syphilis?
- generalised rash
- flu-like symptoms
- meningitis
- nephritis
- “snail-track” mouth ulcers
- neurosyphilis, aseptic meningitis, CN defiicits
Why is an animal model challenging for syphilis?
- because humans are the ONLY HOST for syphilis
What are the non-specific serological tests for syphilis ?
What are these tests useful for?
- VDRL (venereal diseases research lab)
- RPR (rapid plasma reagin)
- to monitor RESPONSE to therapy…(usually negative after successful rx/over time)
When are non-specific serological test for syphilis falsely positive?
- SLE
- Malaria
- Pregnancy
How to dx Primary stage Syphilis?
- PCR
- IgM (+)ve in 1st 2 weeks
- dark ground microscopy
How to dx secondary and tertiary stage Syphilis?
-by serology
If the combined syphilis IgM and IgG screening test comes out as positive , what is then done?
- IgM ELISA
- VDRL test/ RPR
- TPPA test
Rx of syphilis?
- injection of long-acting penicillin
—can’t check sensitivities to syphilis strain as it cannot grow in artificial culture
Why is syphilis known as one of the most sensitive yet resistant bacteria?
- sensitive: smallest penicilin conc. is bactericidal
- resistant: the time for which it MUST BE exposed to, to be killed
What causes genital herpes?
HSV 1 and HSV2
- —enveloped virus containing double stranded DNA
- —spread by genital-genital or oropharyngeal-genital
What is the pathogenesis of genital herpes?
- virus replicates in DERMIS and epidermis
- gets in NERVE endings (why VERY painful)
- multiple small vesicles appear
- —-virus migrates to sacral root ganglion and “hides” —may reactivate later
- —–intermittent “virus SHEDDING” may occur
How to dx herpes?
- swab of virus of deroofed blister for PCR test
- serology (IgG)
How to treat herpes?
- aciclovir
- pain relief
- —pre- and post- exposure vaccines SUCK
How to treat pubic lice?
- Malathion Lotion
How long do the lice live for?
Male: ~22days
Females: 17 days
