Microbiology Flashcards
What is the normal vaginal flora?
Lactobacillus spp
Strep viridans
Group B beta-haemolytic streptococcus
Candida spp
What does Lactobacillus spp produce that suppresses growth of other bacteria?
Lactic acid
Hydrogen peroxide
What % of unselected females are colonised with small numbers of candida and have no symptoms?
30%
What are some predisposing factors for candida infection?
Recent antibiotic therapy
High oestrogen levels (pregnancy, some contraceptions)
Poorly controlled diabetes
Immunocompromised patients
What is the presentation of candida infection?
Intensely itchy white vaginal discharge
How is candida infection diagnosed?
Clinical diagnosis
High vaginal swab for culture- majority of cases C. albicans
What is the treatment for a candida infection?
Topical clotrimazole pessary or cream (OTC)
Oral fluconazole
What organisms are involved in bacterial vaginosis?
Gardnerella vaginalis
Mobiluncus sp.
Others incl. anaerobes
What are the predisposing factors for bacterial vaginosis?
Uncertain
What are the symptoms of bacterial vaginosis?
Thin, watery, fishy-smelling vaginal discharge
How is bacterial vaginosis diagnosed?
Clinical diagnosis
Raised vaginal pH >4.5
What laboratory testing can be carried out in bacterial vaginosis?
HVS sent to lab and examined microscopically to look for presence of clue cells
Subjective/inaccurate test
Hay-Ison scoring system estimates proportions of clue cells to epithelial cells and lactobacilli
What is the treatment for bacterial vaginosis?
Oral metronidazole
What are the 3 classes of prostatitis?
Acute bacterial
Chronic bacterial
Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS)
What are the symptoms of acute bacterial prostatitis?
UTI symptoms
Lower abdo/back/perineal/penile pain and tender prostate on exam
What is acute bacterial prostatitis a rare complication of?
UTI
What organisms cause acute bacterial prostatitis?
Same as UTI- E. coli & other coliforms, enterococcus sp (check for STI in patients <35yo)
How is acute bacterial prostatitis diagnosed?
Clinical signs + MSSU for C&S (+- first pass urine for chlamydia/gonorrhoea)
How is acute bacterial prostatitis treated?
Ciprofloxacin for 28 days (depending on culture result)
Trimethoprim (28d) if high C. diff risk
What are some bacterial causes of STI?
Chlamydia trachomatis (chlamydia) Neisseria gonorrhoeae (gonorrhoea) Treponema pallidum (syphilis)
What are some viral causes of STI?
Human papilloma virus (genital warts)
Herpes simplex (genital herpes)
Hepatitis and HIV
What are some parasitic causes of STI?
Trichomonas vaginalis
Phthirus pubis (pubic lice or “crabs”)
Scabies
Where does chlamydia infect?
Urethra Rectum Throat Eyes Endocervix
What is Chlamydia trachomatis?
Obligate intracellular bacterial with biphasic life cycle (does not reproduce outside host cell or gram stain)
What are the 3 serological groupings of chlamydia trachomatis?
Serovars A-C = Trachoma (eye infection) (NOT an STI)
Serovars D-K = Genital infection
Serovars L1-L3 = Lymphogranuloma venereum
What is the treatment for uncomplicated chlamydia?
Azithromycin- 1g oral
What is the chlamydia infectious cycle?
Attachment and entry
2hrs: Migration to perinuclear area and EB>RB transition
8-24hrs: Inclusion biogenesis and bacterial replication
48hrs: RB>EB transition and cell lysis
Where does Neisseria gonorrhoeae infect?
Urethra Rectum Throat Eyes Endocervix
What is Neisseria gonorrhoeae?
Gram -ve diplococcus
Easily phagocytosed by polymorphs
Fastidious organism
How is chlamydia and gonorrhoea diagnosed?
Combined nucleic acid amplification tests (NAATs) or PCR- tests for both in 1 test
Highly sensitive and specific
How are female patients diagnosed for chlamydia and gonorrhoea?
HVS or vulvo-vaginal swab: either self-taken by patient or clinicial taken or endocervical swab
What can be tested for chlamydia and gonorrhoea other than urine or vaginal swab?
Rectal swab
Throat swab
Eye swab (babies and adults)
What other tests exist for N. gonorrhoeae?
Microscopy for urethral/endocervical swabs (done in SRH clinic)
Culture on selective agar plate (not high vaginal swabs, only SRH to check antibiotic sensitivities and for epidemiology)
(GP swab organism often die during transit)
What are some advantages of PCR/NAATs tests over culture?
Much less invasive specimens required, esp. if patient is asymptomatic (urine ♂; self-taken VVS ♀)
Much more sensitive than culture
Will be positive even if organisms have died in transit to lab
Test takes hours, not days
What are some disadvantages of PCR/NAATs tests over culture?
Cannot test antibiotic sensitivities without culture, so difficult to track antibiotic resistance
Will detect dead organisms (have to wait 5 weeks to do “test of cure” tests)
What is the treatment for N. gonorrhoeae?
IM Ceftriaxone + Oral Azithromycin
What organism causes syphilis?
Spirochaete organism Treponema pallidum (does not gram stain)
How is syphilis diagnosed microscopically?
PCR or serological tests
What are the 4 stages of syphilis?
1y lesion (chancre)
2y stage
Latent stage
Late stage syphilis
Describe the 1y lesion stage of syphilis
Organism multiplies at inoculation site and gets into bloodstream. Chancre will heal without treatment
Describe the 2y stage of syphilis
Large nos. bacteria circulating in blood with multiple manifestations at different sites (snail track mouth ulcers, generalised rash, flu-like symptoms etc)
Describe the latent stage of syphilis
No symptoms, but low-level multiplication of spirochaete in intima of small blood vessels. Can be divided into early and late
Describe late stage syphilis
CV or neurovascular complications many years later
How is syphilis diagnosed?
Dark ground microscopy to look for spirochaetes in exudate from 1y and 2y lesions (not done in Tayside)
Swab of 1y/2y lesions for PCR
Serology-tests for non-specific and specific antibodies to T. pallidum in blood
What are non-specific useful for?
Monitoring response to therapy
Usually -ve after successful treatment
May be falsely +ve (e.g. SLE, malaria, pregnancy)
What specific serological tests exist for syphilis?
TPPA (T. pallidum particle agglutination assay)
TPHA (T. pallidum haemagglutination assay) – not used in Tayside
Specific for syphilis, remain +ve for life
What is used as the screening test for syphilis?
Combined IgG and IgM ELISA
What is the treatment for syphilis?
Penicillin- injectable long acting
What is the cause of genital warts?
HPV
What is HPV?
Non-enveloped icosahedral virus containing double stranded DNA
What types of HPV most commonly cause genital warts?
6 & 11
What types of HPV most commonly cause cervical cancer?
16 & 18
How are genital warts spread?
Close genital skin contact
How is genital warts diagnosed?
Clinical diagnosis
What is the treatment for genital warts?
Cryotherapy
Podophyllotoxin cream/lotion
What vaccine is given to 11-13yo girls for HPV?
Quadrivalent vaccine- immunises against 6,11,16,18
What causes genital herpes?
HSV Type 1 (also causes cold sores) and 2
What is HSV?
Enveloped virus containing double stranded DNA
How is genital herpes spread?
Close contact with someone shedding the virus- genital/genital or oropharyngeal/genital contact
What is the pathogenesis of genital herpes?
1’ infection may be asymptomatic (or very florid)
Virus replicates in dermis/epidermis
Gets into nerve endings of sensory and autonomic nerves
Inflammation at nerve endings> exquisitely painful multiple small vesicles, easily deroofed
Migrates to sacral root ganglion and ‘hides’ from immune system there (for life)
Can reactivate there causing recurrent genital herpes attacks
Intermittent virus shedding can occur in absence of symptoms
How are genital herpes diagnosed?
Swab in virus transport medium of deroofed blister for PCR test
What is the treatment for genital herpes?
Aciclovir helpful if taken early enough
Pain relief
What is trichomonas vaginalis?
Single celled protozoal parasite-divides by binary fission, human host only
How is trichomonas vaginalisis transmitted?
Sexual contact
What does trichomonas vaginalis cause?
Vaginal discharge and irritation in females, and urethritis in males
How is trichomoniasis diagnosed?
HVS for microscopy
PCR available but not in Tayside, so no good test for males
What is the treatment for trichomoniasis?
Oral metronidazole
How are public lice acquired?
Close genital skin contact
What do the lice do to skin?
Bite skin and feed on blood, causes itching
How long do male and female lice live for?
22 and 17 days respectively
Where do female lice lay their eggs
On hair next to skin
What is the treatment for pubic lice?
Malathion lotion
