Microbiology of the GU tract Flashcards
What are the common bacterial STIs?
Chlamydia Trachomatis
Neisseria Gonorrhoeae
Mycoplasma Genitalium
Treponema Pallidum (syphilis)
What are the common viruses that cause STIs?
HPV = genital warts
HSV = genital herpes
Hepatitis
HIV
What parasites can cause STIs?
Trichomonas vaginalis
Phthirus pubis
Scabies
What are the symptoms of goonocci in men?
Intense neutrophilic response that leads to a purulent discharge and pain with urination
Why do you test lots of STIs at the same time?
Gonorrhoea and chlamydia together cause urethritis
Genital ulcers greatly increases the probability of HIV
What organisms are part of the normal vaginal flora?
Lactobacillus predominate (this includes l. crispatus and l. jenseniii)
Group B beta-haemolytic streptococcus
Candida
Strep viridans
What is the function of lactobacillus in the vagina?
Produce lactic acid +/- hydrogen peroxide
What is the normal pH of the vagina?
4-4.5
What is the gram stain of lactobacilli?
Gram positive bacilli
What can be seen when looking at candida albicans down a microscope?
Branching
Hyphae
Yeast
How many women are asymptomatically colonised with candida?
30%
What is the commonest strain of candida?
Candida albicans
What are predisposing factors for C.albicans infection?
Recent antibiotic therapy
High oestrogen levels (pregnancy, contraceptives)
Poorly controlled diabetes
Immunocompromised patients
What is a buzz word for candida infection?
Cottage cheese
How will candida present?
Intensely itchy white vaginal discharge
How is candida diagnosed?
High vaginal swabs for culture
What is the treatment for candida infection?
Topical clotrimazole pessary
Oral fluconazole
How will candida affect men?
Spotty rash of candida balanitis
What is the pathogenesis of gonorrhea infection?
Attaches to host epithelial cells and is endocytosed into cell to replicate within the host cell
Released into the subepithelial space
Typical urethral infections can result in prominent inflammation release of toxic fragments as well as release of chemotactic factors that attract neutrophilic leukocytes
Can cause asymptomatic genital infections
GRAM STAIN OF GONORRHOEA (mooka said she examined)
Gram negative intracellular diplococcus
Where will neisseria gonorrhoeae infect?
Urethra Rectum Throat Endocervix Eyes
Is gonorrhoeae easy to grow?
No; fastidious organisms and will not survive well in less that ideal growth conditions
How is N. gonorrhoeae diagnosed?
Microscopy of urethral/ endocervical swabs (done in SRH clinic)
Culture on selective agar plates
Do you culture all swabs for gonorrhoea?
No; don’t culture high vaginal swabs
Is a NAAT or a culture more effective?
NAAT has an increased sensitivity over culture
Gives you the ability to test urine specimens and self-obtained vaginal swabs
What is the down side to NAAT?
Inability to perform antimicrobial susceptibility testing
Will detect dead organisms - so wait 5 weeks
What is used to treat gonococcus?
Ceftriaxone
Azithromycin
What is the commonest bacterial STI in the uk?
Chlamydia Trachomatis
Can you gram stain chlamydia?
NO; no peptidoglycan in the cell wall, does not reproduce outside a host cell because it is a obligate intracellular bacteria with a biphasic life cycle
What is the treatment for chlamydia?
Doxycycline 100mg bd x 7 days
or you can use azithromycin (1 g oral dose)
What will serovars A-C chlamydia cause?
Eye infection
What will serovars D-K chlamydia cause?`
Genital infection
What will serovars L1-L3 chlamydia cause?
Lymphogranuloma venereum
Who should you screen for Lymphogranuloma venereum?
Tropical areas
Men who have sex with men
What will Lymphogranuloma venereum cause?
Histologically identical to crohn’s; fissures, tenesmus, PR blood
the LAST thing you give to these people is steroids and immunosuppressants - so if the criteria fits SCREEN FOR THIS
How is NAAT used to diagnose chlamydia and gonorrhoea?
Male; first pass urine sample
Female; HVS or vulvovaginal swab
Rectal and throat swabs
Eye swabs; if applicable
What will trichomonas vaginalis cause?
Frothy, purulent discharge
Irritation
Urethritis in males
Describe trichomonas vaginalis?
Single celled protozoal parasite
Divides by binary fission (no cyst formation) - human host only
Transmitted by sexual contact
How is trichomonas vaginalis diagnosed?
High vaginal swab for microscopy (PCR test also available)
What is the treatment for trichomonas vaginalis?
Oral metrondiazole
Describe the symptoms of bacterial vaginosis?
Fishy smelling, thin homogeneous discharge of the vagina
May contain bubbles
What is the positive “whiff” test?
Adding 10% potassium hydroxide to the discharge on the slide elicits an amine-like, fish odor
What will a wet mount in bacterial vaginosis cause?
Absence of bacilli and their replacement with clumps of coccobacilli
CLUE CELL
What are the side effects to untreated bacterial vaginosis?
Increased rate of endometritis or salpingitis
Premature rupture of membranes and preterm delivery
Increased risk of acquisition of HIV
What is the treatment for bacterial vaginosis?
Metronidazole for 7 days
Relapse rate is 30%
Describe the appearance of treponema pallidum (syphilis)
Spirochaete organism
Will not gram stain
Will not grow in artificial culture media, so diagnosis relies on PCR test or on serological blood tests to detect antibodies
What are the 4 stages to syphilis?
Chancre
Secondary stage
Latent stage
Late stage
Describe the chancre seen in syphilis
Organism multiplies at inoculation site and enters blood stream
Will heal without treatment
Describe the secondary stage of syphilis
Large nos. bacteria circulating in blood with multiple manifestations at different sites (snail-track mouth ulcers, generalised rash, flu-like symptoms)
Describe the latent stage of syphilis
No symptoms
Low level multiplication of spirochaete in intima of small blood vessels
Can be divided into early latent and late latent
What is late stage syphilis?
CV or neurovascular complications many years from initial infection
How can syphilis be monitored?
VDRL
RPR
Monitors response to therapy
How can syphilis be diagnosed?
History and examination
Caveats; treatment history, reinfection risk, history, epidemiology
Primary; dark ground microscopy, PCR, IgM
Secondary; serology
Tertiary; serology
What is the treatment for syphilis?
Penicillin
What is the basic screening for syphilis?
IgM and IgG screening test
IF positive
IgM ELISA (? acute), VDRL/ RPR (activity , TPPA (specific)
What causes genital herpes?
HSV 1 and 2
Transmitted by close contact with someone shedding the virus
Spread by genital/genital or oropharyngeal/genital contact
Describe HSV
Enveloped virus containing double-stranded DNA
What is the pathogenesis of HSV?
Primary infection can be asymptomatic OR florid
Virus replicates in dermis and epidermis and enters nerve endings of sensory and autonomic nerves
Inflammation at nerve endings results in exquisitely painful multiple small vesicles, which are early deroofed
Virus migrates to sacral root ganglion and hides from the immune system
Virus can reactivate from there causing recurrent genital herpes
Intermittent virus shedding can occur in the absence of symptoms
How can genital herpes be diagnosed?
Swab in virus transport medium of deroofed blister for PCR test; highly sensitive and specific
Serology but not routinely used
What is the treatment for genital herpes?
Aciclovir
Pain relief
How are pubic lice acquired?
Close genital skin contact
What is the pathogenesis of pubic lice?
Lice bite skin and feed on blood which causes itching in pubic area
Female louse lay eggs on hair
Males will live for 22 days and females for 17 days
What is the treatment for pubic lice?
Malathion lotion
