Microbiology

Question 1

what are the bacterial STIs

Answer 1

Chlamydia trachomatis
Neisseria gonorrhoea
Mycoplasma genitalium
Treponema palladium (syphilis)

Question 2

what are the viral STIs

Answer 2

Human papilloma virus (genital warts)
Herpes simplex (herpes)
Hepatitis and HIV

Question 3

what are the parasitic STIs

Answer 3

trichomonad vaginalis
Phthirus pubis (pubic lice)
Scabies

Question 4

how do you get STI

Answer 4

only human-human transmission

Question 5

why test for multiple STIs at the same time

Answer 5

travel in packs

if have one likely to have another

Question 6

what is the normal pH for a post-pubertal vagina

Answer 6

4-4.5 (ACID)

Question 7

what normal vaginal flora are protective against BV

Answer 7

lactobacillus spp
L.crispatus
L. jensenii

Question 8

what % of females are symptomatically colonised with candida in small numbers

Answer 8

30%

Question 9

what are some predisposing factors for candida

Answer 9

Recent antibiotic therapy
High oestrogen levels
Poorly controlled diabetes
Immunocompromised patients

Question 10

how does candida present

Answer 10

intensely itchy white vaginal discharge

Question 11

how do you diagnose candida

Answer 11

high vaginal swab for culture - majority care caused by Candida albicans

Question 12

how do you treat candida infection

Answer 12

Topical clotrimazole pessary or cream
Oral fluconazole
Non-albicans candida are more likely to be azalea resistant

Question 13

what does neisseria gonorrhoea look like in males

Answer 13

A LOT of puss

Question 14

what is the pathogenesis of GC

Answer 14

attached to epithelial cells and is endocytosed into the cell to replicate within the host cells

released into sub epithelial space

Question 15

what does neisseria gonorrhoea infect

Answer 15

urethra, rectum, throat and eyes, endocervix

Question 16

characteristics of neisseria gonorrhoea

Answer 16

gram negative diplococcus
(looks like 2 kidney beans facing each other)

fastidious organism
-does not survive well in less than ideal growth conditions

Question 17

what tests are done for N.gonorrhoeae

Answer 17

Microscopy of urethra/endocervical swabs

culture on selective agar plates

Nucleic acid amplification tests

Question 18

why do nucleic acid amplification tests

Answer 18

increased sensitivity over culture

can test urine specimens and self obtained vaginal swabs

inability to perform antimicrobial susceptibility testing

will detect dead organisms

Question 19

what is the most common bacterial STI in the UK

Answer 19

chamydia

Question 20

what does chlamydia infect

Answer 20

urethra, rectum, throat and eyes, endocervix

Question 21

characteristics of chlamydia

Answer 21

‘energy parasite’ - does not reproduce outside a hist cell

does NOT stain with gram stain (no peptidoglycan in cell wall)

Question 22

treatment for chlamydia

Answer 22

Doxyxlycline 100mg bd x 7 days

Question 23

what are the 3 serological groupings for chlamydia

Answer 23

Serovars A-C - trachoma (eye infection)
Serovars D-K- genital infection
Servers L1-L3- lymphogranuloma cenereum (in men who have anal sex with men)

Question 24

what serological grouping of chlamydia causes genital infection

Answer 24

serovars D-K

Question 25

how do you diagnose chlamydia

Answer 25

nucleic acid amplification tests or PCR chain reaction

tests for both chlamydia dn gonorrhoea organisms in 1 tests

highly sensitive and specific tests

Question 26

what swabs are taken for chlamydia and gonorrhoea

Answer 26

Male - first pass urine sample
Female - high vaginal swab or vulvo-vaginal swab

rectal and throat swabs

eye swabs

Question 27

presentation of bacterial vaginosis

Answer 27

fishy door yielding a positive ‘whiff’ test (adding potassium hydroxide to the discharge causes the smell)

wet mount reveals absence of bacilli and their replacement with clumps of coccobacili

large numbers of leukocytes in the wet mount of a women with BV suggest a coincident infection

increases susceptibility to HIV

Question 28

what is bacterial vaginosis

Answer 28

imbalance of bacteria in the vagina

too many anaerobes

Question 29

how do you treat BV

Answer 29

directed against the anaerobic flora metronidazole for 7 days

relapse rate is about 30%

treatment of male sexual partners offers no benefit

Question 30

what causes syphilis

Answer 30

treponema pallidum

does not stain with gram stain

cannot be grown in artificial culture media so diagnosis relies on PCR test or on serological tests to detect antibodies

Question 31

how many stages of syphilis is there

Answer 31

4

Question 32

1st stage of syphilis illness

Answer 32

primary lesion
-chancere

organism multiplies at inoculation site and gets into blood stream

cancer will heal without treatment

Question 33

2nd stage of syphilis illness

Answer 33

large nos. bacteria circulating in blood with multiple manifestations at different sites

flu like symptoms, mouth ulcers, tase etc

Question 34

latent stage of syphilis

Answer 34

no symptoms

low level multiplication of spirochaete in intimate of small blood vessels

Question 35

what is the late stage of syphilis

Answer 35

cardiovascular

neuromuscular complications many years later

Question 36

what is a non-specific syphylis test

Answer 36

RPR (rapid plasma reagin)

indicates tissue inflammation

useful for monitoring response to therapy

Question 37

how do you diagnose syphilis

Answer 37

history and examination

caveats

primary – dark ground micrscopy, PCR, IgM

secondary - serology

tertiary - serology

Question 38

treatment for syphilis

Answer 38

penicillin