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Microbiology of Genital Tract Infection Flashcards

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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
What are some features chlamydia trachomatis?
Obligate intracellular bacteria with biphasic life cycle = doesn't reproduce outside host cell Doesn't stain with gram stain
26
What are the three serological groupings of chlamydia trachomatis?
Serovars A-C = trachoma (eye infection, not STI) Serovars D-K = genital infection Serovars L1-L3 = lymphogranuloma venereum (tropical, male/male sex)
27
How is chlamydia treated?
Doxycycline 100mg twice daily for 7 days
28
What are combined NAATS or PCR used to diagnose?
Chlamydia and gonorrhoea = tests for both in 1 procedure
29
What is the mainstay for diagnosing gonorrhoea?
Culture
30
What patients receive combined NAATs testing?
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
What is trichomonas vaginalis?
Single celled protozoal parasite = divides by binary fission (only in human host), transmitted by sexual contact
32
What does trichomonas vaginalis infection cause in females?
Vaginal discharge and irritation
33
How is trichomonas vaginalis infection diagnosed and treated?
``` Diagnosis = high vaginal swab for microscopy Treatment = oral metronidazole ```
34
What is the discharge that occurs in bacterial vaginosis like?
Homogenous and may contain bubbles
35
What is the whiff test performed for bacterial vaginosis?
10% potassium hydroxide added to discharge = positive result produced amine-like fishy odour
36
What does a wet mount of a patient with bacterial vaginosis show?
Absence of bacilli and their replacement with clumps of coccobacilli
37
What can happen to vaginal epithelial cells in bacterial vaginosis?
Some become coated with coccobacilli which obscures their edges (clue cells) or the clear appearance of their cytoplasm
38
What does a large number of leukocytes in a patient with bacterial vaginosis mean?
Suggests coincident infection = patients normally have relatively few polymorphonuclear leukocytes
39
What are some complications of bacterial vaginosis?
Increased rate of upper tract infection = endometritis, salpingitis Premature rupture of membranes and preterm delivery Increased risk of HIV infection
40
What is the treatment for bacterial vaginosis?
Metronidazole for 7 days 30% relapse rate No benefit treating male sexual partners
41
What causes syphilis?
Spirochaete called treponema pallidum = doesn't stain with gram stain
42
Can syphilis be grown on a culture?
No = relies on PCR or serological diagnosis
43
What are the 4 stages of syphilis infection?
Primary (chancre), secondary, latent and late stage
44
What occurs in the primary stage of syphilis?
Organism multiplies at inoculation site and gets into bloodstream, heals without treatment
45
What occurs in the secondary stage of syphilis?
Large number of bacteria circulating in blood with multiple manifestations at different sites
46
What occurs in the latent stage of syphilis?
No symptoms = low level multiplication of bacteria in intima of small blood vessels, divided into early and late periods
47
What occurs in the late stage of syphilis infection?
CV or neurological complications many years later
48
How is syphilis diagnosed?
Primary = dark ground microscopy, PCR, IgM | Secondary and tertiary = specific and non-specific serology
49
What is the diagnostic pathway for syphilis?
Positive ELISA (IgG and IgM) - IgM ELISA or VDRL test/RPR or TPPA test
50
What is the treatment for syphilis?
Long acting injectable penicillin = may need penicillin desensitisation
51
What are some examples of non-specific serological tests?
``` VDRL = venereal diseases research laboratory RPR = rapid plasma reagin ```
52
What are some features of non-serological tests?
Indicate tissue inflammation = may be falsely positive Useful for monitoring therapy response Become negative after successful treatment or over time
53
What causes genital herpes?
HSV type 1 and 2 = enveloped virus containing double-stranded DNA
54
How is genital herpes transmitted?
By close contact with someone shedding HSV = spread by genital/genital contact or oropharyngeal/genital contact
55
Can genital herpes be asymptomatic?
Yes = primary infection may be asymptomatic | Intermittent viral shedding can occur while asymptomatic
56
Where does HSV replicate?
In dermis and epidermis = gets into nerve endings causing inflammation and very painful multiple small vesicles which are easily deroofed
57
Where can HSV hide to become latent?
Hides in sacral root ganglion and can reactivate
58
How is genital herpes diagnosed and treated?
Diagnosed by PCR = swab of deroofed blister in viral transport medium Treatment = aciclovir helpful if taken early enough, pain relief
59
What causes pubic lice?
Phthirus pubis = acquired by close genital skin contact
60
What causes itching in pubic lice infection?
Lice bite skin and feed on blood
61
How long do pubic lice live for?
Females live for 17 days and lay eggs in hair | Males live for 22 days
62
How are pubic lice treated?
Malathion lotion

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