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Reproduction > Microbiology of Genital Tract Infection > Flashcards

Microbiology of Genital Tract Infection Flashcards

1
Q

what are the bacterial types of STIs?

A 
chlamydia trachomatis (chlamydia)
neisseria gonorrhoeae (gonorrhoea)
mycoplasma genitalium 
treponema pallidum (syphilis)
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2
Q

what are the viral types of STIs?

A

HPV (genital warts)
herpes simplex (genital herpes)
hepatitis and HIV

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3
Q

what are the parasitic types of STIs?

A

trichomonas vaginalis
phthirus pubis (pubic lice or crabs)
scabies

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4
Q

which two STIs cause urethritis?

A

gonorrhoea

chlamydia

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5
Q

which STI greatly increases the probability of HIV acquisition?

A

genital ulcers

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6
Q

which type of bacteria predominates in normal vagina flora?

A

lactobacillus spp eg L.crispatus and L.jesenii

  • l.acidophilus not significant part of flora
  • other organisms which can be present are group B beta haemolytic strep, candida (small numbers) or strep viridans group
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7
Q

why is an acid pH (4 to 4.5) normal within vagina?

A

because lactobacillus spp produce lactic acid +/- hydrogen peroxide

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8
Q

what are possible predisposing factors for candida?

A

recent antibiotic therapy
high oestrogen levels (pregnancy, certain types of contraceptives)
poorly controlled diabetes
immunocompromised patients

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9
Q

what % of females are asymptomatically colonised with small numbers of candida?

A

30%

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10
Q

how does candida normally present?

A

intensely itchy white vaginal discharge

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11
Q

how is candida diagnosed?

A

often clinical

high vaginal swab for culture (most caused by c albicans)

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12
Q

what is the treatment for candida infection?

A

topical clotrimazole pessary or cream (available OTC)
oral fluconazole

*non-albicans candida species more likely to be azole resistant

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13
Q

what type of candida presents as a spotty rash and is far less common and not sexually transmitted?

A

candida balanitis

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14
Q

what type of discharge is associated with gonorrhoea infection?

A

purulent

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15
Q

what is the pathogenesis of GC?

A

attaches to host epithelial cells and is endocytosed into the cell to replicate within the host cell and are released into subepithelial scape

typical urethral infections result in inflammation release of toxic lipo-oligosaccharide and peptidoglycan fragments as well as release of chemotactic factors that attract neutrophilic leukocytes

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16
Q

why may some gonococcal strains selectively cause asymptomatic genital infection?

A

because of the differences in organisms ability to bind complement-regulatory proteins that downregulate the production of chemotactic peptides

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17
Q

where in the body does neisseria gonorrhoeae infect?

A

urethra, rectum, throat and eyes (male and female)

endocervix (female)

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18
Q

what type of bacteria is neisseria gonorrhoeae?

A

gram negative diplococcus

  • looks like 2 kidney beans facing each other
  • easily phagocytosed by polymorphs, so often appear intracellularly in gram film
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19
Q

neisseria gonorrhoeae is a fastidious organism - what does this mean?

A

does not survive well in less than ideal growth conditions eg outside body

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20
Q

how is gonorrhoea tested for?

A

microscopy of urethral / endocervical swabs

culture on selective agar plates (done on endocervical, rectal and throat swabs but not high vaginal swabs)

21
Q

what are the benefits nucleic acid amplification tests (NAATs)?

A

increase in sensitivity over culture, ability to test urine and self obtained vaginal swabs

22
Q

what are the downfalls of NAATs?

A

inability to perform antimicrobial susceptibility testing

poor/inadequately defined positive predictive value of some NAATs when used to test low prevalence populations

23
Q

NAATs only detect living organisms - true or false?

A

false - will detect dead organisms so have to wait 5 weeks to do “test of cure” tests

24
Q

where does chlamydia trachomatis infect?

A

urethra, rectum, throat and eyes (male and female)

endocervix (female)

25
Q

what type of bacteria is CT?

A

obligate intracellular bacteria with biphasic life cycle - “energy parasite”

  • does not reproduce outside a host cell
  • does not stain with gram stain (no peptidoglycan in the cell wall)
26
Q

what are the three serological groupings of CT?

A

serovars A-C = trachoma (eye infection, not STI)
serovars D-K = genital infection
serovars L1-L3 = lymphogranuloma venereum

27
Q

what is the treatment of CT?

A

azithromycin (1g oral dose) for uncomplicated chlamydia

doxycycline 100mg bd x 7 days

28
Q

NAATs or PCR tests can be done for chlamydia and gonorrhoea - how are these performed?

A 
male - first pass urine sample 
female - VVS (self taken) or clinician taken endocervical swab (if having speculum exam)
rectal and throat swabs (can be self taken)
eye swabs (babies and adults)
29
Q

what type of bacteria is trichomonas vaginalis?

A

single celled protozoal parasite

*divides by binary fission (no cyst form is known) - human host only

30
Q

what are the symptoms of trichomonas vaginalis?

A

vaginalis discharge and irritation in females

urethritis in males

31
Q

how is trichomonas vaginalis diagnosed?

A

high vaginal swab for microscopy

32
Q

what is the treatment of trichomonas vaginalis?

A

oral metronidazole

33
Q

what may discharge contain in bacterial vaginosis?

A

bubbles

34
Q

what is meant by a “positive whiff test” in bacterial vaginosis?

A

adding 10% potassium hydroxide to discharge on slide elicits an amine-like fishy odour

35
Q

what does a wet mount reveal in bacterial vaginosis?

A

absence of bacilli and their replacement with clumps of coccobacilli

*large numbers of leukocytes suggest a coincident infection, possibly trichomoniasis or bacterial cervicitis

36
Q

BV can cause an increased rate of what type of infection?

A

upper tract (endometritis, salpingitis)

also HIV

37
Q

what can be serious consequences of BV?

A

premature rupture of the membranes and preterm delivery

38
Q

how is BV treated?

A

metronidazole for 7 days

  • relapse rate 30%
  • treatment of male sexual partners offers no benefit
39
Q

syphilis does not stain with gram stain - true or false?

A

true

40
Q

how is syphilis diagnosed?

A

PCT test (reference labs) or on serological (blood) test to detect antibodies

*cannot be grown in artificial culture media

41
Q

what are four stages of syphilis infection?

A

primary (chancre) - will heal without tx

secondary - snail track mouth ulcers, generalised rash, flu like symptoms

latent stage - no symptoms but multiplication of spirochaete in intima of small blood vessels

late stage - CV or NV complications many years later

42
Q

how is syphilis diagnosed?

A

primary - dark ground microscopy, PCR, IgM

secondary and tertiary - serology (specific and non-specific)

43
Q

how is syphilis treated?

A

injectable long-acting preparations of penicillin

*penicillin desensitisation may be required

44
Q

what types of virus is HSV?

A

enveloped virus containing double stranded DNA

45
Q

what is the pathogenesis of genital herpes?

A

primary infection may be asymptomatic
virus replicates in dermis and epidermis
gets into nerve endings of sensory and autonomic nerves
inflammation at nerve endings = painful multiple small vesicles
virus migrates to sacral root ganglion
virus can reactivate from there causing recurrent genital herpes
intermittent virus shedding can occur in absence of symptoms

46
Q

how is genital herpes diagnosed?

A

swab in virus transport medium of deroofed blister for PCR test

serology (IgG but not really used for diagnosis)

47
Q

how is genital herpes treatment?

A

aciclovir may be helpful if taken early enough (famciclovir / valaciclovir)
pain relief

48
Q

how do pubic life (phthirus pubis) cause symptoms?

A

lice bite skin and feed on blood which causes itching in pubic area
female louse lays eggs on hair

  • males live for 22 days
  • females for 17
49
Q

how is pubic lice treated?

A

malathion lotion

Reproduction (45 decks)

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