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Reproduction > Microbiology of Genital Tract Infection > Flashcards

Microbiology of Genital Tract Infection Flashcards

1
Q

What are some common bacterial causes of STIs?

A

Chlamydia trachomatis, neisseria gonororhoeae, mycoplasma genitalium, treponema pallidum

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2
Q

What are some common viral causes of STIs?

A

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

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3
Q

What are some parasites that cause STIs?

A

Trichomonas vaginalis, phthirus pubis (pubic lice), scabies

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4
Q

What do gonococci that infect the male urethra cause?

A

Generally produce intense neutrophil response causing purulent discharge and dysuria

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5
Q

What bacterial STIs cause urethritis?

A

Gonorrhoea and chlamydia

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6
Q

What do genital ulcers increase the probability of?

A

HIV infection

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7
Q

What bacterial predominate in the normal vaginal flora?

A

Lactobacillus spp = mostly L. crispatus and L. jensenu, produce lactic acid and hydrogen peroxide

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8
Q

What is the normal pH of the vagina?

A

Acidic = pH of 4-4.5

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9
Q

What are some other organisms that can be present in the normal vaginal flora?

A

Group B strep and strep viridans

30% colonised symptomatically with small numbers of candida

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10
Q

What causes most candida infections?

A

Candida albicans = intensely itchy white vaginal discharge

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11
Q

What are the risk factors for candida infection?

A

Recent antibiotic therapy, high oestrogen levels, pregnancy, poorly controlled diabetes, immunocompromised

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12
Q

How is candida infection diagnosed?

A

Often clinical

Can do high vaginal swab for culture

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13
Q

What is the treatment for candida infection?

A

Topical clotrimazole pessary/cream
Oral fluconazole
Non-albicans species more likely to be resistant

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14
Q

What are some features of candida balanitis infection?

A

Causes characteristic spotty rash

Less common and not sexually transmitted

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15
Q

What does gonorrhoea bacteria do once it has attached to epithelial host cells?

A

Endocytosed into cell to replicate within the host cell = released into subepithelial space

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16
Q

What do typical urethral gonorrhoea infections cause?

A

Prominent inflammation, release of toxic lipo-oligosaccharides and peptidoglycan fragments as well as release of chemotactic factors that attract neutrophilic leukocytes

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17
Q

Is gonorrhoea always symptomatic?

A

No = some strains selectively cause asymptomatic genital infection

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18
Q

What is neisseria gonorrhoea?

A

Gram negative diplococcus = look like two kidneys facing each other. often appear intracellularly on gram film, doesn’t survive well outside body

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19
Q

What are some features of neisseria gonorrhoea infection?

A

Much less common than chlamydia

Infects urethra, rectum, throat, eyes and endocervix

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20
Q

How is neisseria gonorrhoea diagnosed?

A

Microscopy of urethral/endocervical swabs = done in SRH, 90+% specificity in males but less in females
Culture on selective agar plates = not suitable for high vaginal swabs, only done in SRH in Tayside

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21
Q

What are the benefits for NAATs?

A

More sensitive than culture and able to test urine specimens and self obtained vaginal swabs

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22
Q

What are the limits of NAATs?

A

Can’t perform antimicrobial susceptibility testing and have poor positive predictive value when used to test low prevalence populations

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23
Q

Why do you have to wait 5 weeks before using NAAT to test for a cure?

A

It can detect dead organisms

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24
Q

What is the most common bacterial STI in the UK?

A

Chlamydia = infects urethra, rectum, endocervix, throat and eyes

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25
Q

What are some features chlamydia trachomatis?

A

Obligate intracellular bacteria with biphasic life cycle = doesn’t reproduce outside host cell
Doesn’t stain with gram stain

26
Q

What are the three serological groupings of chlamydia trachomatis?

A

Serovars A-C = trachoma (eye infection, not STI)
Serovars D-K = genital infection
Serovars L1-L3 = lymphogranuloma venereum (tropical, male/male sex)

27
Q

How is chlamydia treated?

A

Doxycycline 100mg twice daily for 7 days

28
Q

What are combined NAATS or PCR used to diagnose?

A

Chlamydia and gonorrhoea = tests for both in 1 procedure

29
Q

What is the mainstay for diagnosing gonorrhoea?

A

Culture

30
Q

What patients receive combined NAATs testing?

A

Male patients = first pass urine sample
Female patients = high vaginal or vulvovaginal swab or clinician taken endocervical swab if getting speculum
Rectal and throat swabs, and eye swabs in babies and adults

31
Q

What is trichomonas vaginalis?

A

Single celled protozoal parasite = divides by binary fission (only in human host), transmitted by sexual contact

32
Q

What does trichomonas vaginalis infection cause in females?

A

Vaginal discharge and irritation

33
Q

How is trichomonas vaginalis infection diagnosed and treated?

A 
Diagnosis = high vaginal swab for microscopy
Treatment = oral metronidazole
34
Q

What is the discharge that occurs in bacterial vaginosis like?

A

Homogenous and may contain bubbles

35
Q

What is the whiff test performed for bacterial vaginosis?

A

10% potassium hydroxide added to discharge = positive result produced amine-like fishy odour

36
Q

What does a wet mount of a patient with bacterial vaginosis show?

A

Absence of bacilli and their replacement with clumps of coccobacilli

37
Q

What can happen to vaginal epithelial cells in bacterial vaginosis?

A

Some become coated with coccobacilli which obscures their edges (clue cells) or the clear appearance of their cytoplasm

38
Q

What does a large number of leukocytes in a patient with bacterial vaginosis mean?

A

Suggests coincident infection = patients normally have relatively few polymorphonuclear leukocytes

39
Q

What are some complications of bacterial vaginosis?

A

Increased rate of upper tract infection = endometritis, salpingitis
Premature rupture of membranes and preterm delivery
Increased risk of HIV infection

40
Q

What is the treatment for bacterial vaginosis?

A

Metronidazole for 7 days
30% relapse rate
No benefit treating male sexual partners

41
Q

What causes syphilis?

A

Spirochaete called treponema pallidum = doesn’t stain with gram stain

42
Q

Can syphilis be grown on a culture?

A

No = relies on PCR or serological diagnosis

43
Q

What are the 4 stages of syphilis infection?

A

Primary (chancre), secondary, latent and late stage

44
Q

What occurs in the primary stage of syphilis?

A

Organism multiplies at inoculation site and gets into bloodstream, heals without treatment

45
Q

What occurs in the secondary stage of syphilis?

A

Large number of bacteria circulating in blood with multiple manifestations at different sites

46
Q

What occurs in the latent stage of syphilis?

A

No symptoms = low level multiplication of bacteria in intima of small blood vessels, divided into early and late periods

47
Q

What occurs in the late stage of syphilis infection?

A

CV or neurological complications many years later

48
Q

How is syphilis diagnosed?

A

Primary = dark ground microscopy, PCR, IgM

Secondary and tertiary = specific and non-specific serology

49
Q

What is the diagnostic pathway for syphilis?

A

Positive ELISA (IgG and IgM) - IgM ELISA or VDRL test/RPR or TPPA test

50
Q

What is the treatment for syphilis?

A

Long acting injectable penicillin = may need penicillin desensitisation

51
Q

What are some examples of non-specific serological tests?

A 
VDRL = venereal diseases research laboratory 
RPR = rapid plasma reagin
52
Q

What are some features of non-serological tests?

A

Indicate tissue inflammation = may be falsely positive
Useful for monitoring therapy response
Become negative after successful treatment or over time

53
Q

What causes genital herpes?

A

HSV type 1 and 2 = enveloped virus containing double-stranded DNA

54
Q

How is genital herpes transmitted?

A

By close contact with someone shedding HSV = spread by genital/genital contact or oropharyngeal/genital contact

55
Q

Can genital herpes be asymptomatic?

A

Yes = primary infection may be asymptomatic

Intermittent viral shedding can occur while asymptomatic

56
Q

Where does HSV replicate?

A

In dermis and epidermis = gets into nerve endings causing inflammation and very painful multiple small vesicles which are easily deroofed

57
Q

Where can HSV hide to become latent?

A

Hides in sacral root ganglion and can reactivate

58
Q

How is genital herpes diagnosed and treated?

A

Diagnosed by PCR = swab of deroofed blister in viral transport medium
Treatment = aciclovir helpful if taken early enough, pain relief

59
Q

What causes pubic lice?

A

Phthirus pubis = acquired by close genital skin contact

60
Q

What causes itching in pubic lice infection?

A

Lice bite skin and feed on blood

61
Q

How long do pubic lice live for?

A

Females live for 17 days and lay eggs in hair

Males live for 22 days

62
Q

How are pubic lice treated?

A

Malathion lotion

Reproduction (62 decks)

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