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Reproduction and Sexual Health > Microbiology of STI's > Flashcards

Microbiology of STI's Flashcards

1
Q

Give 3 examples of bacterial causes of STI’s.

A
  • Chlamydia trachomatis (chlamydia)
  • Neisseria gonorrhoeae (gonorrhoea)
  • Treponema pallidum (syphilis)
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2
Q

Give 3 examples of viral causes of STI’s.

A
  • Human papilloma virus (genital warts)
  • Herpes simplex (genital herpes)
  • Hepatitis and HIV
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3
Q

Give 3 examples of parasitic causes of STI’s.

A
  • Trichomonas vaginalis
  • Phthirus pubis (pubic lice or “crabs”)
  • Scabies
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4
Q

Describe the response generally produced by gonococci that infects the male urethra.

A

An intense neutrophil response that leads to a purulent discharge and pain on urination

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5
Q

Describe the response generally produced by chlamydia that infects the male urethra.

A

More likely to produce a mild, watery discharge, or no sx at all

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6
Q

What is transmission of STI’s solely?

A

Human-human

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7
Q

What organism, is the exception to human-human transmission and has some inanimate sources?

A

T. vaginalis

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8
Q

What does the efficacy of transmission depend on?

A
  • Concentration of phenotype of that organism in the genital tract
  • Susceptibility of the sexual partner
  • Resistance of the host (hereditary, acquired or innate)
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9
Q

Immunity is ____

A

RARE

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10
Q

Re-infection is ______

A

COMMON

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11
Q

What % of females are colonised with small amounts of flora and have no symptoms?

A

30%

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12
Q

Give the 4 predisposing factors to candida infection.

A
  • Recent antibiotics
  • High oestrogen levels
  • Poorly controlled diabetes
  • Immunocompromised patients
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13
Q

What 3 things would predispose someone to high oestrogen levels?

A
  • Pill

* Pregnancy

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14
Q

How does a candida infection present?

A

As an intensely itchy white vaginal discharge

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15
Q

How is candida infection diagnosed?

A

This is a CLINICAL DIAGNOSIS.

Do a high vaginal swab for culture!

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16
Q

What are the majority of cases of candida infection caused by?

A

C. albicans.

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17
Q

How is candida infection treated?

A

Topical clotrimazole pessary or cream (available OTC).

Oral fluconazole.

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18
Q

What are the important features of a gram film of someone with candida?

A

Budding + Hyphae

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19
Q

In men, what does candida infection present as?

A

A ‘spotty’ rash of Candida balanitis

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20
Q

What are the 3 classes of prostatitis?

A
  1. Acute bacteria
  2. Chronic bacterial
  3. Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS)
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21
Q

Acute bacterial and chronic bacterial prostatitis account for

A

<5%

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22
Q

What signs + symptoms does acute bacterial prostatitis present with?

A 
UTI symptoms
\+
* Lower abdomen pain
* Back pain
* Perineal pain
* Penile pain
* Tender prostate on examination
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23
Q

What are the signs + symptoms of a UTI?

A
  • Dysuria
  • Frequency of urination + nocturnal
  • Haematuria
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24
Q

What symptoms are associated with an upper UTI?

A
  • Fever
  • Loin pain
  • Rigors
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25
Q

In men, what is prostatitis a rare complication of?

A

UTI

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26
Q

What organisms can cause prostatitis?

A

Same organisms as UTI – E coli and other coliforms, Enterococcus sp.
BUT . . .
Check for STI in patients <35years (gonorrhoea, chlamydia).

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27
Q

How is prostatitis diagnosed?

A 
Clinical signs
\+
MSSU (mid-stream specimen of urine) for culture and sensitivity
\+
First pass urine for STI's
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28
Q

From what part of the stream, is urine taken for an STI check in males?

A

First pass

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29
Q

From what part of the stream, is urine taken for an UTI check in males?

A

Mid-stream

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30
Q

How is prostatism treated?

A

Ciprofloxacin for 28days – altered depending on culture result.
Trimethoprim for 28days – if high C diff risk. (in Tayside, we much prefer trimethoprim)

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31
Q

How would gonorrhoea appear on a gram film?

A

As gram negative intracellular diplococci

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32
Q

Why are confections common?

A

STI pathogens move together

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33
Q

What do genital ulcers highly increase the probability of?

A

HIV acquisition

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34
Q

What can STI’s cause?

A

Urethritis

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35
Q

What bacteria predominates in the ‘healthy’ vagina?

A

Lactobacillus spp

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36
Q

What does lactobacillus produce? What is the effect of this?

A

Lactic acid +/- hydrogen peroxide

  • These suppress growth of other bacteria
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37
Q

Give examples of organisms that may also be part of the normal vaginal flora.

A
  • Strep ‘viridans’ – there are many different species within this group.
  • Group B beta-haemolytic Streptococcus.
  • Candida spp. (small numbers)
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38
Q

What does normal vaginal flora contain?

A

Hydrogen peroxide-producing lactobacilli, such as Lactobacillus crispatus and Lactobacillus jensenii

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39
Q

What is the purpose of normal vaginal flora?

A

Help ‘defend’ the vagina against a number of pathogens (an e.g. of innate immunity).

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40
Q

What Lactobacillus is rarely found in the normal vagina? What does this explain

A

Lactobacillus acidophilus.

Explains the failure of yogurt to serve as a remedy for or as a preventive for BV.

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41
Q

What is the normal pH of the vagina? When does it increase?

A

4-4.5

Increases in bacterial vaginosis

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42
Q

In bacterial vaginosis, what is the normal vaginal flora replaced by?

A

Gardnerella vaginalis and many species of anaerobic bacteria

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43
Q

What, essentially, is bacterial vaginosis?

A

An imbalance of vaginal flora

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44
Q

Describe the discharge in bacterial vaginosis.

A

Homogenous (like a film), and may contain bubbles

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45
Q

Describe how to carry out a ‘whiff test’ for bacterial vaginosis. Describe a positive result.

A

Add 10% potassium hydroxide to the discharge on a slide.

This elicits an amine-like, fishy odour due to the amines from the anaerobic flora.

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46
Q

What are the results from a wet mount in a sample from a patient with bacterial vaginosis

A
  • Absence of bacilli, and their replacement with clumps of coccobacilli.
  • Some vaginal epithelial cells are coated with coccobacilli, which may obscure their edges (clue cells), or the normally clear appearance of the cytoplasm.
  • Relatively few polymorphonuclear leukocytes are observed.
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47
Q

What does large numbers of leukocytes in the wet mounts of a patient with bacterial vaginosis.

A

A coincident infection, possibly trichomoniasis or bacterial cervicitis

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48
Q

Describe the gram stain of someone with bacterial vaginosis. (BUZZWORD !!!)

A

Epithelial ‘clue cells’ covered with gram variable bacilli

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49
Q

What (in terms of infection) is this associated with increased risk of in someone with bacterial vaginosis?

A

Upper tract infection – endometritis, salpingitis

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50
Q

In relation to pregnancy, what is BV associated with an increased risk of?

A

Premature rupture of the membranes and preterm delivery

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51
Q

What may women with BV have an increased risk of?

A

HIV

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52
Q

What is the treatment of BV directed against?

A

Anaerobic flora

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53
Q

How is BV treated?

A

Metronidazole for 7 days

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54
Q

What is the BV relapse rate?

A

30%

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55
Q

Who does the treatment of BV not help?

A

Male partners

56
Q

What is the commonest STI in the UK?

A

Chlamydia

57
Q

Where in the body does chlamydia infect?

A
  • Urethra
  • Rectum
  • Throat
  • Eyes
  • Endocervix
58
Q

What type of bacteria is chlaymdia?

A

Obligate intracellular bacteria with biphasic life cycle – “energy parasite”

Does NOT reproduce outside a host cell

59
Q

What does chlamydia behave like?

A

A parasite

60
Q

Does chlamydia gram stain?

A

No – because there is no peptidoglycan in the cell wall

61
Q

Outline the different serological groupings of chlamydia.

A

Serovars A-C = Trachoma (eye infection) (NOT an STI)
Serovars D-K = Genital infection
Serovars L1-L3 = Lymphogranuloma venereum

62
Q

Serovars D-K is what type of infection?

A

STI - thick DicK

63
Q

Serrovasrs A-C is what type of infection?

A

Eye (trachoma) - think ‘A canny c’ - c-see

64
Q

Serovars L1-L3 is what type of infection? Describe this.

A

Lymphogranuloma venereum

  • Seen in MSM
65
Q

How is serovars L1-L3 tested for?

A

Look for chlamydia trachomatis serovars L1-L3

66
Q

How is serovars L1-L3 treated?

A

With doxycycline for 3 weeks

67
Q

How can serovars present?

A

Can present with a proctitis which histologically mimics Crohn’s, rectal bleeding, pain and tenesmus.

68
Q

How is chlamydia treated?

A

Doxycycline 100mg bd x 7 days

69
Q

What test, tests for both chlamydia and gonorrhoea at the same time?

A

Combined nucleic acid amplification tests (NAATs)
OR
Polymerase chain reaction test (PCR).

70
Q

NAATs and PCR are highly ________ and _________ tests

A
  • Specific

* Sensitive

71
Q

Outline what samples are taken in a STI test for chlamydia and gonorrhoea.

A
  • Male pts – FIRST PASS urine sample
  • Female pts – HVS or vulvo-vaginal swab (VVS), which can be self-taken by pt or clinician taken endocervical swab (if pt is having speculum examination).
  • Rectal and throat swabs (can be self-taken).
  • Eye swabs (babies and adults).
72
Q

Why is first pass urine taken in an STI test and not MSSU?

A

Not MSSU as want urine to come from urethra).

73
Q

Outline the pathogenesis of gonorrhoea.

A

Attaches to host epithelial cells and is endocytosed into the cell to replicate within the host cell and are released into the subepithelial space.

74
Q

What do urethral infections usually result in?

A

Prominent inflammation.
Release of toxic lipo-oligosaccharide and peptidoglycan fragments, as well as the release of chemotactic factors that attract neutrophilic leukocytes

75
Q

What do some gonococcal strains selectively cause?

A

Asymptomatic genital infection

76
Q

The discharge in gonorrhoea is ________

A

Purulent

77
Q

What is the appearance on gram film of neisseria gonorrhoea?

A

Gram negative diplococcus.

  • look like ‘2 kidney beans facing each other.’
  • easily phagocytosed by polymorphs, so often appear intracellularly on a Gram film.
78
Q

Neisseria gonorrhoea is described as a fastidious organism’, what does this mean?

A

Does not survive well in less than ideal growth conditions ie. outside the body

79
Q

Name 2 tests that can be done to look for neisseria gonorrhoea.

A
  • Microscopy of urethral/endocervical swabs.

* Culture on selective agar plates

80
Q

What does selective agar do?

A

Suppress growth of normal flora

81
Q

What does pharyngeal gonococcal infection result from?

A

Orogenital exposure

82
Q

Pharyngeal gonococcal infection is more efficiently acquired by fellatio (oral sex act on male) than by cunnilingus (oral sex act on female)

A

TRUE

83
Q

What % of MSM with genital tract gonorrhoea have the infection in the pharynx too?

A

10-30%

84
Q

Gonorrhoea infection is usually symptomatic

A

FALSE - usually asymptomatic

85
Q

What is the treatment for N. gonorrohoea in the UK?

A

Intramuscular ceftriaxone + oral azithromycin

86
Q

After treatment for gonorrhoea, what is recommended for all patients?

A

Test of cure

87
Q

How is rectal gonorrhoea diagnosed?

A

The identification of N. gonorrhoeae, usually by NAAT

88
Q

Who, is screening for rectal gonorrhoea routine in?

A

MSM

89
Q

Greater than 50% of MSM with gonorrhoea will have?

A

ONLY extragenital infections

90
Q

What is syphilis caused by?

A

The spirochaete organism, Treponema pallidum

91
Q

What does treponema palladium NOT do?

A

Stain with a gram stain

92
Q

What does diagnosis of syphilis rely on?

A

PCR test (reference labs)
OR
Serological (blood) tests to detect antibodies.

*As the organism cannot be grown in artificial culture media.

93
Q

How many stages are there do the illness of syphilis?

A

4

94
Q

Outline the 4 different stages of syphilis.

A
  1. Primary lesion (chancre) - organism multiplies at inoculation site and gets into bloodstream. Chancre (painless ulcer at site of contact) will heal without treatment
  2. Secondary stage – large nos. bacteria circulating in blood with multiple manifestations at different sites (“snail-track” mouth ulcers, generalised rash, flu-like symptoms etc.)
  3. Latent stage – no symptoms, but low-level multiplication of spirochaete in intima of small blood vessels. Can be divided into early latent and late latent periods

** Some patients will self-cure or be treated co-incidentally **

  1. Late stage syphilis – cardiovascular or neurovascular complications many years later
95
Q

Where, commonly, is the rash of secondary syphilis found?

A

Palms and soles

96
Q

What kind of microscopy is done for syphilis?

A

Dark background microscopy

97
Q

Describe the swab for PCR in syphilis.

A

Swab primary or secondary lesions sent to reference lab for PCR

98
Q

What does serology of syphilis look for?

A

Tests for non-specific and specific antibodies to T. pallidum in blood

99
Q

What do non- specific test for syphilis indicate? What are they useful in?

A

How active the disease is and are useful to monitor the response to treatment

100
Q

What do specific test for syphilis do?

A

Confirm the diagnosis.

BUT antibody levels decrease very slowly even after successful treatment, and often remain positive for life.

101
Q

Name 2 of these non-specific serological tests.

A

VDRL – venereal diseases research laboratory.

RPR – rapid plasma reagin.

102
Q

What do non-specific tests indicate?

A

Tissue inflammation

103
Q

When may non-specific tests for syphilis be falsely positive?

A

SLE, malaria, pregnancy.

104
Q

What is RPR, the non-specific test for syphilis used for?

A

Monitoring response to therapy

105
Q

When does non-specific tests become negative?

A

After successful treatment

106
Q

Give 2 examples of specific serological tests.

A
  • TPPA (T. pallidum particle agglutination assay)

* TPHA (T. pallidum haemagglutination assay)

107
Q

TPHA remains positive for ____ but is not ________ for syphilis

A

LIFE

Specific

108
Q

What is used as the “screening” test for syphilis?

A

Combined IgG & IgM ELISA.

109
Q

There are lots of false positives when testing for syphilis

A

TRUE

110
Q

What is always used to follow response to treatment for syphilis?

A

RPR

111
Q

What is syphilis very sensitive to?

A

PENICILLIN !!!!

112
Q

What penicillin preparation is used to treat syphilis?

A

Injectable long-acting preparations of penicillin (unless pt is penicillin hypersensitive).

113
Q

Why can labs not grow the organism and check sensitivities for syphilis?

A

The organism cannot be grown in artificial culture medium

114
Q

What is genital herpes caused by?

A

Herpes simplex virus type 1 (also causes ‘cold sores’) and type 2.

115
Q

Describe the herpes simplex virus.

A

Enveloped virus, containing double-stranded DNA

116
Q

What is herpes transmitted by?

A

Close contact with someone shedding the virus

117
Q

How is herpes spread?

A

By either genital/genital or oropharyngeal/genital contact.

118
Q

What may the primary infection in syphilis be like?

A

Asymptomatic (or very florid).

119
Q

Where does the herpes virus replicate?

A

In the dermis and epidermis.

120
Q

What does the HERPES virus get into? What does this result in?

A

Gets into nerve endings of sensory and autonomic nerves.

Results in inflammation at nerve endings  exquisitely painful multiple small vesicles, which are easily deroofed

121
Q

Where does the herpes virus migrate to?

A

The sacral root ganglion.
- ‘hides’ from the immune system (probs remains for life).

  • virus can reactivate from there causing recurrent genital herpes attacks (trigger factors for this not understood)
122
Q

In the absence of symptoms in herpes, what can occur?

A

Intermittent virus shedding.

123
Q

How is genital herpes diagnosed?

A

Swab in virus transport medium of deroofed blister for PCR test - highly sensitive and specific

124
Q

How is herpes treated?

A
  • ACICLOVIR may be helpful if taken early enough.

* Pain relief.

125
Q

What is Trichomonas vaginalis?

A

A single-celled protozoal parasite

126
Q

How does Trichomonas vaginalis divide?

A

By binary fission – no cyst form is known

127
Q

What type of host does TV live in?

A

Human only

128
Q

How is TV transmitted?

A

Sexual contact

129
Q

What symptoms does TV cause?

A

Vaginal discharge and irritation in females

Urethritis in males

130
Q

How is TV diagnosed?

A

High vaginal swab for microscopy (PCR test also available, but not used in Tayside, so no good test for males)

131
Q

How is TV treated?

A

With oral metronidazole

132
Q

How is pubic lice acquired?

A

By close genital skin contact

133
Q

How do pubic lice act?

A

Lice bite skin and feed on blood, causing itching in the pubic area

134
Q

On average, how long do i) male ii) female lice live for?

A

i) 22 days.

ii) 17 days.

135
Q

What is used to treat pubic lice?

A

Malathion lotion.

Reproduction and Sexual Health (51 decks)

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