Microbiology Flashcards
what organism predominates normal vaginal flora
lactobacillus spp
give 2 examples of lactobacillus that are part of the normal vaginal flora
lactobacillus crispatus
lactobacillus gensenii
how are lactobacillus protective
produce lactic acid +/- hydrogen peroxide making the vagina acidic so pathogenic organisms dont grow
give 3 other examples of normal vaginal flora
group B b-haemolytic strep
small no of candida sp (mainly albicans)
strep viridans
give 4 PDFs for candida infection
recent antibiotic tx
high oestrogen levels
poorly controlled diabetes
immunocompromised (non-albicans)
how does candida infection present
intensely itchy white vaginal discharge
how is candida infection diagnosed
high vaginal swab of posterior fornix of vagina for culture
most candida infections are what type
albicans
how is candida infection treated
topical clotrimazole pessary or cream (OTC) oral fluconazole (one dose)
what is the issue with treating non-albicans candida infection
more likely to be azole resistant
what kind of candida would cause typical spotty rash on penis which is not an STI
candida balanitis
what kind of organism is gonorrhoea
gram negative diplococcus
gonorrhoea diplococci look like
2 kidney beans facing eachother
does gonorrhoea appear intra or extracellular on gram film
intracellular
how does gonorrhoea become intracellular
easily phagocytosed by polymorphs
gonorrhoea is a fastidious organism - what does this mean
doesn’t survive well in less than ideal conditions
where can gonorrhoea infect
mucous membranes of the ... urethra rectum throat eyes endocervix
how does gonorrhoea of the rectum or throat present
usually asymptomatic
how does gonorrhoea replicate
attaches to host epithelial cells and is endocytosed into the cell to replicate within the host and then released into subepithelial space
gonorrhoea is more/less common than chlamydia and is more common in women/men
less common than chlamydia
more common in men
how does gonorrhoea present in males
purulent urethral discharge
dysuria
what % of gonorrhoea in males in asymptomatic
10
how does gonorrhoea present in females
purulent urethral discharge
dysuria
pelvic pain
what % of gonorrhoea in females is asymptomatic
50
how is gonorrhoea diagnosed
NAAT screening test for C + G
what sample is used for gonorrhoea dx for NAAT in males
first pass urine
what sample is used for gonorrhoea dx for NAAT in females
vulvovaginal swab
gonorrhoea can also be cultured on what agar
selective agar plate - suppresses growth of normal flora - kills competitors
in what case would you not need to use selective agar
when no competing flora is expected e.g. synovium
why is culture not done in a GP
only done in SRHC as if in GP organism dies on way to lab
culture of gonorrhoea can be done of what samples
endocervical, rectal, throat swabs
not high vaginal swabs
what is an advantage of doing a culture
can test antibiotic susceptibility
what is the treatment for gonorrhoea
IM ceftriaxone + azithromycin
what is used if IM is CI to treat gonorrhoea
cefixime oral
when should a test of cure be done for gonorrhoea
at least 2 weeks later
there is a higher risk of ____ to ___ transmission of gonorrhoea than ____ to ____
male to female than female to male
what is the commonest STI in the UK
chlamydia trachomatis
what kind of organism is chlamydia
gram negative obligate intracellular bacterium
what does obligate intracellular bacterium mean
cannot live/reproduce outside host cell
what word describes the life cycle of chlamydia
biphasic
what colour does chlamydia stain
doesnt stain
why does chlamydia not stain
no peptidoglycan in the cell wall - typical lipopolysacarhide
why does chlamydia not stain
no peptidoglycan in the cell wall - typical lipopolysaccharide wall of GN bacteria
what are the 3 serological groups of chlamydia
serovars A-C
serovars D-K
serovars L1-L3
A-C causes what
trachoma
D-K causes what
genital infection
L1-L3 causes what
lymphogranuloma venereum - infection of the lymph nodes
who gets LGV
MSM
how does LGV present
usually presents in MSM with proctitis
- rectal pain/discharge/bleeding
- tenesmus
with LGV there is a high risk of what
concurrent STI e.g. HIV
what can chlamydia infect
urethra rectum throat eyes endocervix
what age group has the highest incidence of chlamydia
20-24 year olds
how does chlamydia present in males
watery urethral discharge dysuria urethritis epididymo-orchitis proctitis (LGV)
what % of males with chlamydia are asymptomatic
50%
what % of females with chlamydia are asymptomatic
70%
how does chlamydia present in females
post-coital or IM bleeding
lower abdominal pain
watery discharge
dyspareunia
the NAAT test is highly ____ and ____
sensitive and specific
what samples are taken for a NAAT test in females
vulvovaginal swab
what samples are taken for NAAT test in males
1st pass urine
what samples are taken for NAAT test in a symptomatic female (chlamydia)
high vaginal swab or endocervical swab
if chlamydia is transmitted to neonate it can cause
conjunctivitis
pneumonia
when can a NAAT test be done for chlamydia
2 weeks post exposure
what is the treatment for chlamydia
doxycycline 100mg bd x 7 days
what is the risk of tubal blockage after one episode of chlamydia
10%
what is the risk of tubal blockage after 3 episodes of chlamydia
50%
what % of PID is due to chlamydia
50%
what is mycoplasma genitalium
non-gonococcal STI that can cause PID
how is mycoplasma genitalium dx
NAAT - VVS or FPU
high levels of macrolide
mycoplasma genitalium presents how
usually asymptomatic carriage
what kind of organism is trichomonas vaginalis
single celled protozoal parasite
how does trichomonas vaginalis divide
binary fission (no cyst form is known
how is trichomonas vaginalis transmitted
STI or inanimate source e.g. sex toy
how does trichomonas vaginalis present in males
urethritis
how does trichomonas vaginalis present in females
vaginal discharge and irritation
how is trichomonas vaginalis dx
HVS for microscopy
no good test for males
how is trichomonas vaginalis treated
oral metronidazole
what is the pathogenesis of bacterial vaginosis
lack of balance - normal flora replaced by anaerobic bacteria
give 2 examples of anaerobic organisms that replace normal flora in bacterial vaginosis
gerdernella vaginalis
mobiluncus
what cells are seen in bacterial vaginosis
clue cells
what are clue cells
absence of bacilli and replacement with clumps of coccobacilli which coat some vaginal epithelial cells obscuring edges (clue cells) and obscuring normally clear cytoplasm
how does bacterial vaginosis present
intensely smelly frothy bubbly vaginal discharge
positive whiff test
what is the positive whiff test
adding 10% KOH to discharge elicits amine like fishy odour
the vaginal pH in bacterial vaginosis becomes more
alkaline
> 4.5
the vaginal pH in bacterial vaginosis becomes more
alkaline
> 4.5
in bacterial vaginosis there is a ___ level of polymorphonuclear leukocytes
few
high number would suggest coincidental infection possibly trichomoniasis or bacterial cervicitis
there is an increased risk of what with bacterial vaginosis
HIV contraction
PROM and preterm delivery
what is the treatment of bacterial vaginosis
metronidazole 7 days
what causes pubic lice
Phthirus pubis
how is pubic lice contracted
close genital skin contact
how long do male lice live for
22 days
how long do female lice live for
17 days
why are pubic lice itchy
bite skin and feed on blood
female lice lay eggs on hair
how is pubic lice treated
malathion lotion
how is sensitivity calculated
true positive / true positive + false negative
how is specificity calculated
true negative / true negative + false positive
how is positive predictive value calculated
true positive / true positive + false positive
how is negative predictive value calculated
true negative / true negative + false negative
gonococci that infect the male urethra produce an intense ______ response leading to purulent discharge
neutrophil
STIs tend to
coexist
is reinfection common
yes
genital ulcers greatly increases risk of what
acquiring HIV
what 2 STIs tend to co-exist
NG and CT
what organism causes syphilis
treponema pallidum
what kind of organism is treponema pallidum
spirochaete
what 5 ways can syphilis be transmitted
STI during birth trans-placental blood transfusion non-sexual transmission to health care workers
what are the 4 stages of syphilis
primary lesion
secondary stage
latent stage
late stage
what is chancre
painless ulcer that is a primary lesion in syphilis
what is the incubation period of a primary syphilis lesion
21 days
how does primary lesion of syphilis progress
organism multiplies at the innoculation site and gets into blood stream
non-tender local lymphadenopathy is what stage of syphilis
primary lesion
will chancre need treatment
will heal without treatment
90% of primary syphilis lesions are found where
genital
what happens in the secondary syphilis stage
large no of bacteria circulating in blood with multiple manifestations at different sites
what happens in the secondary syphilis stage
large no of bacteria circulating in blood with multiple manifestations at different sites
what are some examples of secondary lesions (6)
snail track ulcers generalised rash (macular, follicular or pustular) flu like symptoms lesions of mucous membranes generalised lymphadenopathy patchy alopecia
where is the generalised rash of secondary syphilis found
palms and soles mainly
what is condylomata lata
highly infectious lesion in syphilis found on genitals - exudes a serum teaming with treponemes
what is the incubation period of secondary syphilis
6 weeks to 6 months
what are the symptoms of the latent stage of syphilis
no symptoms
the latent phase can be subdivided into early latent and late latent
of the 2 which is infectious
early latent - infectious
late latent - non-infectious
what is seen in the late stage of syphilis
cardiovascular or neurovascular complications many years later
what stages of syphilis are infectious
primary lesion
secondary stage
early latent
what gait is seen in the late stage of syphilis
high stamping gate
what causes the high stamping gate seen in the late stage of syphilis
loss of proprioception due to tarbes so rely on ears to find out where feet are
what is tarbes
slow degeneration of neural tracts (particularly DCML) in syphilis - loss of touch, vibration and proprioception
dissemination occurs early/late in syphilis
early
what subspecies of treponema causes syphilis
pallidum
what subspecies of treponema causes Yaws
pertenue
what subspecies of treponema causes bejel
endemicum
what subspecies of treponema causes pinta
carateum
does syphilis stain with gram stain
no
can syphilis be grown in artificial culture
no
how is syphilis tested
PCR or serological blood test to detect antibodies
what does the baseline blood test for suspected syphilis test for
(ELISA test)
syphilis IgM and IgG
ELISA test is carried out on what specimen
clotted blood specimen
what 3 ways can primary syphilis be tested
dark ground microscopy
PCR
IgM
how can secondary and tertiary syphilis be tested
serology
what are some specific serological tests for syphilis
TPPA
IgM ELISA
INNO-LIA
FTA-abs
what test is +ve for life in syphilis
TPPA (treponema pallidum particle agglutination)
what test screens for syphilis
IgM ELISA
what is the treatment of syphilis
benzylpenicillin (injectable penicillin)
can you check syphilis sensitivities
no because it cant be grown but syphilis remains very sensitive to penicillin
what happens if someone is allergic to penicillin but has syphilis
desensitisation
what is the dose time ratio of syphilis
very low dose but must be exposed for a long time
what is the reason for the dose time ratio of syphilis
slow rate of replication
what is a nick name for syphilis and why
the great imitator
mimics other diseases
what is a nick name for syphilis and why
the great imitator
mimics other diseases
what type of HSV causes cold sores
both can
Type 1 more common
describe the herpes simplex virus
enveloped virus containing double stranded DNA
how is HSV transmitted
close contact with someone shedding the virus (genital - genital or oropharyngeal - genital etc)
describe the pathogenesis of HSV
virus duplicates in epidermis and dermis and gets into sensory nerve endings and autonomic nerve endings
inflammation at nerve endings due to HSV causes what
intensely painful multiple small vesicles which are easily deroofed
how may primary infection of HSV present
asymptomatic or very florid
HSV migrates where
sacral root ganglion and hides from immune system
HSV can ____ causing recurrent genital herpes attacks
reactivate
can intermittent virus shedding occur in the absence of symptoms of HSV?
yes
what is the incubation period of primary HSV infection
3-6 days
what is the duration of primary HSV infection
14-21 days
how does primary HSV present
blistering and ulceration of external genitalia pain external dysuria vaginal or urethral discharge local lymphadenopathy
what are the HSV prodromal symptoms
fever and myalgia
recurrent infection is seen more with HSV
2
how often does HSV 2 recur
every 2-3 months
how often does HSV 1 recur
every 1-2 years
HSV recurs more/less as time goes on
less
recurrent HSV infection presents as
unilateral small blisters and ulcers
minimal systemic symptoms that resolve within 5-7 days
how is HSV diagnosed
swab of base of deroofed blister in viral transport medium for PCR
how is HSV diagnosed between recurrences
no good test - serology IgG but not routinely used
what is the treatment of HSV
aciclovir PO 400mg TDS 5 days
famciclovir/valaciclovir
what can be used for pain relief in HSV
topical lidocaine 5% ointment
saline bathing
viral shedding is higher with HSV
2
viral shedding is more frequent during which year of HSV infection
1st year
viral shedding occurs more in people with more/less frequent recurrences
more
what is done if primary attack of HSV occurs in 3rd trimester of pregnancy
c section
what is the risk of transmission if primary attack of HSV occurs in 3rd trimester of pregnancy
50%
HSV transmitted to a neonate would cause what
localised CNS or diseminated disease (latter more common in preterm infants and exclusively in primary infection)
do transplacental antibodies stop HSV spreading to brain of neonate
no
what is done for pregnant women with recurrent HSV attacks
suppressive therapy and advised risk of transmission is very low
what is the most common viral STI in the UK
HPV
what is the lifetime risk of acquiring HPV
80%
describe HPV
major capsid protein (L1) surrounds viral nucleic acid (DNA)
how many types of HPV are there
over 200
how many types of HPV infect anogenital epithelium
> 40
what types of HPV cause anogenital warts
6 and 11
what types of HPV cause palmar and plantar warts
1 and 2
what types of HPV cause cellular dysplasia / intraepithelial neoplasia
16 and 18
can you get HPV from asymptomatic carrier
yes
is transmission of more than 1 type common
yes
what is the incubation period of HPV
3 weeks - 9 months (average 3 months)
what % of HPV warts spontaneously clear
20-35%
what % of HPV clears with treatment
60%
what % of HPV persists
20%
what types are vaccinated against
6 11 16 and 18
who is vaccinated
girls ages 11-13
boys S1 and S2
MSM
what is the 1st line treatment of HPV
podophyllotoxin (warticon)
what is the 2nd line treatment of HPV
imiquimod (aldera)
what is the 3rd line treatment of HPV
cryotherapy/electrocautery
how is HPV diagnosed
clinically
how does acute bacterial prostatitis present
symptoms of UTI but may also have lower abdo pain/ back perineal pelvic pain and tender on prostate exam
what UTI organisms cause acute bacterial prostatitis
e coli and other coliforms
enterococcus sp
what STI organisms cause acute bacterial prostatitis
chlamydia
gonorrhoea
how is acute bacterial prostatitis diagnosed
clinically
MSSU (mid stream specimen of urine) for culture and sensitivity
FPU if think STI
what is the treatment of acute bacterial prostatitis
ciprofloxacin or trimethoprim 28 days
