Microbiology of UTI

Question 1

What increases the probability of HIV acquisition?

Answer 1

Genital ulcers

Question 2

What STIs cause urethritis?

Answer 2

Gonorrhea and chlamydia

Question 3

Describe the normal vaginal flora

Answer 3

Lactobacillus predominate and are protective

Question 4

Why is the normal pH of the vagina acidic?

Answer 4

Lactobacillis produce lactic acid +/- hydrogen peroxide

Question 5

What organisms aside from lactobacillus species are normal vaginal flora?

Answer 5

Group B beta-haemolytic streptococcus

Candida spp.

Strep viridans group

Question 6

What would be seen on a gram film of Candida albicans?

Answer 6

Budding yeasts and hypae

Question 7

Candida infection; ___% of females are asymptomatically ________ with small numbers of mostly candida _______

Answer 7

Candida infection; 30% of females are asymptomatically colonised with small numbers of mostly candida albicans

Question 8

What are the predisposing factors for candida?

Answer 8

• Recent antibiotic therapy
• High oestrogen levels (pregnancy, certain types of contraceptive)
• Poorly controlled diabetes
• Immunocompromised patients

Question 9

What is this infection?

Answer 9

Candida albicans

Question 10

What is the presentation of a candida infection?

Answer 10

Intensely itchy white vaginal discharge

Question 11

How is candida diagnosaed?

Answer 11

High vaginal swab for culture- the majority of cases are caused by candida albicans

Question 12

What are the treatments for candida infections?

Answer 12

• Topical clotrimazole pessary or cream
• Oral fluconazole

Question 13

When might candida infections be resistant to azole treatment?

Answer 13

Non-albicans candida species responsible

Question 14

What is this infection?

How is it acquired

Answer 14

Candida balanitis

Not sexually transmitted

Question 15

What is this infection?

Answer 15

Gonorrhoea

Question 16

Describe the pathogenesis of gonorrhoea?

Answer 16

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

Question 17

How does the inflammation occur in typical urethral gonococcal infections?

Answer 17

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

Question 18

Why are some gonococcal infections asymptomatic?

Answer 18

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

Question 19

What parts of the body does neisseria gonorrhoea infect?

Answer 19

Urethra, rectum, throat & eyes, endocervix

Question 20

Describe the appearance of neisseria gonorrhoea

Answer 20

Looks like 2 kidney beans facing each other

Easily phagocytosed by polymorphs, so often appear intracellularly

Question 21

Neisseria gonorrhoea is a _________ organism, it _______ survive outside the body

Answer 21

Neisseria gonorrhoea is a fastidious organism, it doesn’t survive outside the body

Question 22

How is N. gonorrhoea tested for?

Answer 22

• microscopy of urethral/endocervical swabs (90+% specificity in males)
• culture on selective agar plates

Question 23

Culture on selective agar plates for n. gonorrhoea is done on what samples?

Answer 23

Endocervical, rectal and throat swabs NOT vaginal swabs

Question 24

What does selective agar do?

Answer 24

Suppresses growth of normal flora

Question 25

When can non selective media be used in culture

Answer 25

When no competing flora are expected (synovium)

Question 26

Where are cultures on selective agar plates taken?

Answer 26

Only done in SRH clinic- die in transit

Question 27

What are NAATs

Answer 27

Nucleic Acid Amplification Tests

Question 28

When are NAATs used?

Answer 28

To diagnose gonorrhoea and chlamydia

Question 29

What is the treatment for gonorrhoea?

Question 30

What is the commonest bacterial STI in the UK?

Answer 30

Chlamydia trachomatis

Question 31

Where does chlamydia infect?

Answer 31

Infects the urethra, rectum, throat and eyes, and endocervix

Question 32

Describe the nature of chlamydia trachomatis

Answer 32

Obligate intracellular bacteria with biphasic life cycle- does NOT reproduce outside host cell

Question 33

Which STI does not stain with gram stain

Answer 33

Chlamydia trachomatis

Question 34

What are the three serological groupings of chlamydia trachomatis?

Answer 34

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

Question 35

Describe the chlamydia infectious cycle

Answer 35

- attachment and entry - migration to perinuclear area and EB -\> RB transition - inclusion biogenesis and bacterial replication - RB -\> EB transition and cell lysis (48h)

Question 36

Descirbe the diagnosis of chlamydia and gonorrhoea

Answer 36

Combined NAATs or polymerase chain reaction for both organisms in one test Done on; * male patients- first pass uring sample * female patients- HVS or vulvovaginal swab (can be self-taken by patient or clinician-taken endocervical swab if bhaving speculum examination) * Rectal and throat swabs * Eye swabs (babies and adults)