Microbiology Flashcards
what STIs are commonly seen together
gonorrhoea and chlamydia
genital ulcers (syphilis, herpes) increase the probability of getting HIV
what are normal vaginal flora
lactobacillus (predominant and protective)
L. crispatus and L. jensenii (produce lactic acid)
group B strep
candida (in small numbers)
strep viridans
what is the normal vaginal pH
4-4.5
what are hypae
branches and buds seen on fungi
what is the most common cause of a candida infection
candida albicans
what are the predisposing factors to a candida infection
recent antibiotic therapy
high oestrogen levels (pregnancy, contraceptives)
poorly controlled diabetes
immunocompromised
what is the presentation of a candida infection
intensely itchy white thick ‘cottage cheese’ vaginal discharge
how do you diagnose candida infections
often clinical
can do high vaginal swab
what is the treatment for candida
topical clotrimazole pessary/ cream (OTC)
oral fluconazole
can men get candida infections
yes can get candida balanitis but less common
is candida sexually transmitted
no
what is the pathogenesis of a gonococcal infection
attaches to host epithelial cells
is endocytosed into the cells to replicate
released into subepithelial space
typically cause prominant inflammation due to release of toxic lipo-oligosaccharide factors and pepitoglycan fragments
some can be asymptomatic
what is seen on gram stain of gonorrhoea
gram -ve intracellular diplococcus
where can N gonorrhoeae infect
urethra, rectum, throat and eyes
endocervix in women
N gonorrhoea is fastidious, what does this mean
dies easily if not in ideal growth conditions
what is more common chlamydia or gonorrhoea
chlamydia
what tests for gonorrhoea
microscopy of swabs on selective agar plates (not for high vaginal swabs)
NAAT (higher sensitivity than culture, can test urine and vaginal swabs, cant test sensitivities to antibiotics, can detect dead organisms (wait 5 weeks for test of cure), only do if person at risk as false positives)
what is the commonest STI in the UK
Chlamydia Trachomatis
where can Chlamydia Trachomatis infect
urethra, rectum, throat, eyes and endocervix in women
what is the pathogenesis of Chlamydia Trachomatis
intracellular bacteria with biphasic life cycle
cannot replicate ouside a host cell
can you see Chlamydia Trachomatis on a gram stain
no has no peptidoglycan in the cell wall
what serological group of Chlamydia Trachomatis causes genital infections
serovars D-K
what is the treatment for Chlamydia Trachomatis
Doxycycline 100 mg bd x 7 days
erythromycin, ofloxacin are other options
what test can diagnose both chlamydia and gonorhoeae in one go
NAATs or PCR males- first pass urine sample female- HVS/ vulvo vaginal swab rectal and throat swabs eye swabs
what are the pros and cons of nucleic acid amplification tests
slight increase in sensitivity over culture, the ability to test urine specimens and self-obtained vaginal swabs
Inability to perform antimicrobial susceptibility testing and the poor or inadequately defined positive predictive value of some NAATs when they are used to test low-prevalence (<1%) populations
what is Trichomonas vaginalis
single cells protozoal parasite that infects human hosts only
how is Trichomonas vaginalis transmitted
sexual contact
what does a Trichomonas vaginalis cause
yellowish, frothy and purulent vaginal discharge and irritation in females
can cause urethritis in males
how is Trichomonas vaginalis diagnosed
high vaginal swab for microscopy
what is the treatment for Trichomonas vaginalis
oral metronidazole
what causes bacterial vaginosis
dont know, lots of different things
coccobacilli
lots of anaerobes
what is the presentation of bacterial vaginosis
fishy smelling, thin, homogenous discharge
what is bacterial vaginosis associated with
upper tract infections (endometritis, salpingitis)
premature ruptureof membranes and preterm delivery
increased risk of HIV acquisition
what is the treatment for bacterial vaginosis
is drirected against the anaerobic flora
metronidazole for 7 days
does treatment of male partners help in bacterial vaginosis
no, but can cause urethritis so if symptomatic yes
what causes syphilis
spireochaete organisms treponema pallidum
can you see syphilis on a gram stain
no
how is syphilis diagnosed
dark ground microscopy, PCR or serological blood tests to look for antibodies
cannot be grown in artificial culture media
what are the stages of illness in syphilis
primary lesion- painless chancre, organism multiplies at inoculation site (site of contact), gets into bloodstream, chanre will heal without treatment
secondary- large numbers of bacteria in blood with multiple manifestations (snail track mouth ulcers, generalised rah, flu like symptoms)
latent stage- no symptoms, low level multiplication in intima of small blood vessels
later stage syphilis- cardiovascular (aortic aneurysms), neurovascular complications many years later
some will self cure/ be treated co- incidentally
what are non specific serological tests
e.g. VDRL, RPR
indicate tissue inflammation, used n syphilis
useful in monitoring response to therapy
usually become negative after successful treatment OR over time
can be falsely positive (SLE, malaria, pregnancy)
how do you diagnose primary syphilis
dark ground microscopy, PCR, IgM
how do you diagnose secondary syphilis
serology (specific and non specific)
how is teriary syphilis diagnosed
serology (specific and non specific)
what is the pathway for syphilis serological testing
syphilis combined IgM and IgG screening test (ELISA test on clotted blood specimen) = if negative no more tests = if positive: IgM ELISA (specific) VDRL/ RPR (non specific) TPPA (specific)
what is the treatment for syphilis
injectable long acting penicillin
why does penicillin have to be long acting to treat syphilis
as syphilis has slow rate of replication
what causes genital herpes
herpes simplex virus type 1 (usually cause mouth cold sores) and 2
what type of organism is HSV
enveloped virus containing double stranded DNA
how is genital herpes transmitted
close contact with someone shedding the virus
genital/ genital or oropharyngeal/ genital contact
what is the pathogenesis of genital herpes
primary infection may be asymptomatic (or very florid)
virus replicates in dermis and epidermis
gets into nerve endings (sensory and autonomic)
inflammation at nerve endings (v painful multiple small vesicles, easily deroofed)
virsu migrates to sacral root ganglion where it becomes latent, can reactivate at any time
intermittent virus shedding can occur in the absence of symptoms
how is herpes diagnosed
swab in virus transport medium of deroofed blister for PCR
serology - for partner wanting to know risk of getting it from partner
what treatment for genital herpes
aciclovir
pain relief
what organisms is pubic lice
phthirus pubis
how are pubic lice spread
close genital skin contact
what is the pathogenesis of pubic lice
lice bite skin and feed on blood - itching in pubic area
female louse lays eggs on hair
what is the treatment for pubic lice
malathion lotion
what is the treatment for gonorrhoea
swab every site infected for culture
IM ceftriaxone
how are gonorrhoea and chlamydia primarily diagnosed
PCR (NAATs) testing
what other infections should you test for in a patient with gonorrhoea
HIV, syphilis, hep B and C
after exposure when do you know if they have HIV
4 weeks
when do you need to retest gonorrhoea after treatment- why
6 weeks- as lots of resistance
what general advice for thrush (candida infection)
avoid irritants (soaps, emollients) wear cotton nickers if recurring maybe change contraceptives if high oestrogen pill
what candida is an aids defining infection
oesophageal candida
what specific is needed from females to test for chlaymdia and gonorrhoea
vulvovaginal (self taken) swan
how is bacterial vaginosis acquired
sexual intercourse
why is it important to diagnose HSV
To offer appropriate counselling. If lesion was mimicking a dermatomal distribution (recurring HSV can go on buttocks) so to differentiate it from herpes varicella zoster. Also if pregnant need to know so can prevent baby getting herpes encephalitis
was causes genital warts
human papilloma virus types 6 and 11
what treatment for genital warts
nothing, 30% will resolve in 3 months
podophyllotoxin cream
iminquimod
cryotherapy
what vaccine can reduce incidence of genital warts
HPV
what are the specific syphilis serological tests
TPPA
TPHA (not used in tayside)
specific for syphilis but remain positive for life
IgM and IgG ELISA
combined and used as screening test for syphilis
can you use specific serological tests to monitor response of syphilis to treatment
TPPA, TPHA no- stay positive for life
what is IgM ELISA a marker of
recent, untreated infection
should be viewed as indication of active syphilis infection
what is TPPA a marker of
positive for life in anyone who has/ has had syphilis
what is VDRL a marker of
untreated active infection
what does positive IgG mean in syphilis
can be active, latent, treated or congenital
IgG + IgM +
IgM +
TPPA +
VRDL +
primary/ secondary syphilis
IgG + IgM +
IgM -
TPPA +
VRDL +/-
latent syphilis
IgG + IgM +
IgM -
TPPA +
VRDL +/-
latent untreated syphilis
IgG + IgM +
IgM -
TPPA +
VRDL -
old treated syphilis
IgG + IgM +
IgM +
TPPA +
VRDL +
congenital
