Genito-urinary infections II

Question 1

How are STDs transmitted?

Answer 1

Sexual activity with no barrier is used and exchange of fluid or contact with mucosal epithelium occurs

Question 2

Why are STDs rising in the UK?

BUT stabilised in 2011

Answer 2

Difficult to change behaviour

Absence of vaccines

Question 3

What’s the most common STD?

Answer 3

Chlamydia

Question 4

List the main organisms that cause STDs?

Answer 4

Neisseria gonnorhoea  >>> Gonnnorhoea
Chlamydia trachomatis  >>> chlamydia
Treponema pallidum >>> Syphilis
HIV virus- elsewhere
Genital Herpes - elsewhere
Hepatitis B- elsewhere

Question 5

N. gonorrhoeae (Gonoccus) features?

Answer 5

Exclusively a fully virulent human pathogen;
- never found as a commensal
Asymptomatic carrier state: mainly females
Acute urethritis
- in 95% males
- only ~ 50% women show discharge, dysuria

Ascend to Fallopian tubes

• acute salpingitis, pelvic inflammatory disease
• sterility

Question 6

What is Ophthalmia neonatorum?

Answer 6

Infant blindness

Question 7

Cause of oral gonnorhea?

Answer 7

very rare, but can result from oral sex with infected man

Question 8

N. gonorrhoeae pathogenesis

Answer 8

Surface pili- pil proteins- attachment

Opa proteins- aid attachment

Lipo-ologosaccharide: sialylated- complement resistance- host mimicry

Por proteins- nucleate actin aiding cell invasion

Possesses IgA protease- aids survival inside host cells

= Phase and antigenic variation contribute to pathogenicity and hinder vaccine development

Question 9

How does N.gonorrhoeae pathogenesis travel? What does it cause?

Answer 9

Release into bloodstream disseminates infection to other sites fever, arthiritis (1-3% women, much lower in men), endocarditis

Question 10

N. gonorrhoeae epidemiology?

Answer 10

1980s = increased condom usage = decreased infection
Increasing again now due to promiscuity, travel and use of oral contraceptives

Co-infec of HIV and N.gonorrhoeae increases transmission by 500%
Infection with N.gonorrhoeae increases likelihood of contracting HIV 5x

Question 11

How to diagnose STDs?

Answer 11

Susceptible to dessication, so transport medium used
Sub-culture on chocolate agar
Sugar fermentation tests–glucose +ve
Oxidase test positive

Question 12

How to treat STDs?

Answer 12

Contact tracing- antibiotic prophylaxis of contacts
Historically penicillin and tetracyclines were drugs of choice
Ceftriaxone (IM) and azithromycin (1g orally) recommended first line choice (also kills chlamydia).
Many 3rd world strains are Penicillin and Tetracycline resistant, susceptibility tests must be performed

Question 13

Syphilis: Treponema pallidum features?

Answer 13

Treponema: Trepein (Gr) – to turn; nēma (la)- thread
Unculturable  in vitro
Exclusively Human pathogen
3rd most frequent STD in USA
Major third-world problem

Question 14

How is Syphilis: Treponema pallidum transmitted?

Answer 14

Sexual contact via minute skin abrasions

Vertical transmission- cross placental: Congenital syphilis

Question 15

Symphilis progression?

Answer 15

1, Initial contact - treponema multiplies

2. 2-10 weeks for primary syphilis to develop
   - Enlarged inguinal nodes
   - Prolif of treponemas in lymph nodes
3. 1-3 months - 2ndry syphilis
   - Flu like illness
   - Mucocutaneous rash
   - Lesions in lymph nodes, liver, skin etc
4. 2-6 weeks - latent syphilis
   - Treponemas dormant in liver or spleen
5. 3-30yrs Tertiary syphilis
   - Nuerosyphilis
   - CV syphilis

Question 16

How are Syphilis: Treponema pallidum and HIV linked?

Answer 16

Co-infection with HIV common
Hinders treatment
Increases infectivity and spread of HIV

Question 17

Congenital syphilis causes what?

Answer 17

Transmitted cross-placenta

• Can lead to still-birth
• Congenital infection
• Birth deformities, silent infection – presents as facial and tooth deformities at 2 years of age

Question 18

How to treat congenital syphilis?

Answer 18

Cheap effective testing kits

Question 19

What is the most common STI in the UK?

Answer 19

Chlamydia trachomatis

Question 20

Chlamydia trachomatis features?

Answer 20

115,000 new cases in 2009 (out of 383,000 STIs in total)
Often asymptomatic in females
50% symptomatic in males
Re-infection common as immunity weak
Incubation period 7 – 14 days
Disease due to direct damage to cells and immunopathology causing fibrosis and scarring
Can also cause conjunctivitis- common co-occurence.

Question 21

What are the serotypes of chlamydia trachomatis?What can Chlamydia cause?

Answer 21

Serotypes:

• A-C: trachoma (eye infec)
• D-K: Cervicitis, urethritis, conjunctivitis
• L1-3: LGV severe venereal disease

Common cause of conjunctivitis
Also in neonates- infection in birth
Major cause of blindness worldwide
with 6 million cases of blindness due to trachoma
-not STI in true sense

Question 22

Chlamydia Infection in Men?

Answer 22

Asymptomatic infection ~ 50%
Non specific urethritis 
Strong associations with: 
	Acute epididymitis
	Prostatitis
	Male infertility

Question 23

Chlamydia Infection in Women?

Answer 23

Asymptomatic infection ~ 70 %
Mucopurulent cervicitis
Urethral infection

Pelvic inflammatory disease in up to 40% - ascending infection involving uterus, fallopian tubes, and other pelvic structures
Complications include chronic pelvic pain, ectopic pregnancy and infertility

Question 24

Features of chlamydia?

Answer 24

Very small obligate intracellular parasite
Small genome
Enters through minute abrasions
Specialised life-cycle
Seems to avoid and not stimulate immune responses

Question 25

Chlamydia has a restricted cell range?

Answer 25

Prefers to infect non-ciliated columnar and cubiodal epithelium: genital tract from urethra up to fallopian tubes and rectum
Also respiratory and conjunctival cells

Question 26

What to do if you’re infected with chlamydia?

Answer 26

Tests are available on NHS:
Culture in cells
Direct immunofluorescence and ELISA
PCR tests (known as NAAT)

Question 27

How to treat chlamydia?

Answer 27

Azithromycin (single dose).

Doxycycline (longer course).