Microbiology Flashcards
what are the bacterial STIs
Chlamydia trachomatis
Neisseria gonorrhoea
Mycoplasma genitalium
Treponema palladium (syphilis)
what are the viral STIs
Human papilloma virus (genital warts)
Herpes simplex (herpes)
Hepatitis and HIV
what are the parasitic STIs
trichomonad vaginalis
Phthirus pubis (pubic lice)
Scabies
how do you get STI
only human-human transmission
why test for multiple STIs at the same time
travel in packs
if have one likely to have another
what is the normal pH for a post-pubertal vagina
4-4.5 (ACID)
what normal vaginal flora are protective against BV
lactobacillus spp
L.crispatus
L. jensenii
what % of females are symptomatically colonised with candida in small numbers
30%
what are some predisposing factors for candida
Recent antibiotic therapy
High oestrogen levels
Poorly controlled diabetes
Immunocompromised patients
how does candida present
intensely itchy white vaginal discharge
how do you diagnose candida
high vaginal swab for culture - majority care caused by Candida albicans
how do you treat candida infection
Topical clotrimazole pessary or cream
Oral fluconazole
Non-albicans candida are more likely to be azalea resistant
what does neisseria gonorrhoea look like in males
A LOT of puss
what is the pathogenesis of GC
attached to epithelial cells and is endocytosed into the cell to replicate within the host cells
released into sub epithelial space
what does neisseria gonorrhoea infect
urethra, rectum, throat and eyes, endocervix
characteristics of neisseria gonorrhoea
gram negative diplococcus
(looks like 2 kidney beans facing each other)
fastidious organism
-does not survive well in less than ideal growth conditions
what tests are done for N.gonorrhoeae
Microscopy of urethra/endocervical swabs
culture on selective agar plates
Nucleic acid amplification tests
why do nucleic acid amplification tests
increased sensitivity over culture
can test urine specimens and self obtained vaginal swabs
inability to perform antimicrobial susceptibility testing
will detect dead organisms
what is the most common bacterial STI in the UK
chamydia
what does chlamydia infect
urethra, rectum, throat and eyes, endocervix
characteristics of chlamydia
‘energy parasite’ - does not reproduce outside a hist cell
does NOT stain with gram stain (no peptidoglycan in cell wall)
treatment for chlamydia
Doxyxlycline 100mg bd x 7 days
what are the 3 serological groupings for chlamydia
Serovars A-C - trachoma (eye infection)
Serovars D-K- genital infection
Servers L1-L3- lymphogranuloma cenereum (in men who have anal sex with men)
what serological grouping of chlamydia causes genital infection
serovars D-K
how do you diagnose chlamydia
nucleic acid amplification tests or PCR chain reaction
tests for both chlamydia dn gonorrhoea organisms in 1 tests
highly sensitive and specific tests
what swabs are taken for chlamydia and gonorrhoea
Male - first pass urine sample
Female - high vaginal swab or vulvo-vaginal swab
rectal and throat swabs
eye swabs
presentation of bacterial vaginosis
fishy door yielding a positive ‘whiff’ test (adding potassium hydroxide to the discharge causes the smell)
wet mount reveals absence of bacilli and their replacement with clumps of coccobacili
large numbers of leukocytes in the wet mount of a women with BV suggest a coincident infection
increases susceptibility to HIV
what is bacterial vaginosis
imbalance of bacteria in the vagina
too many anaerobes
how do you treat BV
directed against the anaerobic flora metronidazole for 7 days
relapse rate is about 30%
treatment of male sexual partners offers no benefit
what causes syphilis
treponema pallidum
does not stain with gram stain
cannot be grown in artificial culture media so diagnosis relies on PCR test or on serological tests to detect antibodies
how many stages of syphilis is there
4
1st stage of syphilis illness
primary lesion
-chancere
organism multiplies at inoculation site and gets into blood stream
cancer will heal without treatment
2nd stage of syphilis illness
large nos. bacteria circulating in blood with multiple manifestations at different sites
flu like symptoms, mouth ulcers, tase etc
latent stage of syphilis
no symptoms
low level multiplication of spirochaete in intimate of small blood vessels
what is the late stage of syphilis
cardiovascular
neuromuscular complications many years later
what is a non-specific syphylis test
RPR (rapid plasma reagin)
indicates tissue inflammation
useful for monitoring response to therapy
how do you diagnose syphilis
history and examination
caveats
primary – dark ground micrscopy, PCR, IgM
secondary - serology
tertiary - serology
treatment for syphilis
penicillin
