L36 - Sexually transmitted diseases

Question 1

Define the reservoir, site of entry and transmission of STDs?

Answer 1

Reservoir = asymptomatic human carriers, do not survive in environment

Entry:

• Mucous membrane +/- trauma
• Minute abrasion in skin surface
• Local sites: vagina, cervix, urethra, rectum, pharynx, eye)

Question 2

Define the public health centers for STD?

Answer 2

Department of health Social hygiene clinics

Question 3

Most common STI in HK?

Answer 3

Non-gonococcal urethritis/ nonspecific genital infection by Chlamydia trachomatis

Question 4

3 typical clinical presentation features of STDs?

Answer 4

1. Urethral discharge (urethritis/male).
2. Genital ulcer (male and female)
3. Genital lumps (male/female)

Question 5

List 2 main pathogens that cause urethral discharge/ urethritis?

Answer 5

• Neisseria gonorrhoeae
• Chlamydia trachomatis

(Asymptomatic: Ureaplasma urealyticum, Mycoplasma genitalium)

(Rare: Herpes Simplex virus, Trichomonas vaginalis, yeasts)

Question 6

Compare gonococcal and Non-gonococcal urethritis: onset, incubation period, relapse?

Answer 6

Gonococcal:

• 2-5 days
• Abrupt onset
• Rare relapse

Non-gonococcal:

• 7-14 days
• Gradual onset
• Common relapse

Question 7

Compare gonococcal and Non-gonococcal urethritis: dysuria, discharge?

Answer 7

Gonococcal:

• Prominent dysuria
• Copious discharge

Non-gonococcal:

• Mild dysuria
• Scanty, non-purulent discharge

Question 8

List infections caused by Chlamydia trachomatis serotype A,B,C?

Answer 8

Trachoma

Question 9

List infections caused by Chlamydia trachomatis serotype D to K?

Answer 9

Cervicitis, urethritis, pelvic inflammatory disease, neonatal pneumonia

Question 10

List infections caused by Chlamydia trachomatis serotype L?

Answer 10

Lymphogranuloma venereum (LGV)

Question 11

List infections caused by Chlamydophila/ Chlamydia pneumoniae?

Answer 11

Respiratory tract infection (not genital)

Question 12

How to clinically establish presence of urethritis?

Answer 12

1. P/E
2. Microscopy: swab for anterior surface of urethra, anal mucosa, endocervix:
   - 1st swab for Gonococcal culture
   - 2nd swab for Chlamydia culture

Question 13

Which serotypes of chlamydia cause STDs?

Answer 13

D to L

Question 14

Define the medium and culture for gonococcal urethritis?

Answer 14

Modified Thayer-Martin medium (nutritive culture media with antibiotics): small, grayish-white mucoid colonies

Incubation: 35 oC, CO2 enriched, humid atmosphere

Never refrigerate, immediate culture

Question 15

Define the medium and culture for Chlamydial urethritis?

Answer 15

• Need special transport medium and cell culture: McCoy Cell Line shows Chlamydia inclusion bodies
• Can refrigerate for 24h

Question 16

Name one test for rapid chlamydia urethritis Dx and give 2 limitations?

Answer 16

Antigen detection e.g. Chlamydiazyme

–Less sensitive than culture

–False-positive results from cross reacting bacterial species

Question 17

Describe the morphology of gonococci and gram stain?

Answer 17

Gram-negative diplococci

small mucoid colonies

Question 18

Pharyngeal gonorrhoea is often asymptomatic in normal adults. T or F?

Answer 18

True

Question 19

Name one test for pharyngeal gonorrhea?

Answer 19

Direct fluorescent antibody (DFA) for gonococcal pharyngitis

Question 20

Name one test for detecting both gonococcal and chlamydial urethritis simultaneously? Give 2 advantages?

Answer 20

nucleic acid amplification tests (NAAT): e.g. PCR

Higher sensitivity than culture
Performed on non-invasive specimens (e.g. first-void urine)

Question 21

Treatment for urethritis?

Answer 21

• Single dose oral azithromycin/ 7 days oral doxycycline for chlamydial
• Single dose intramuscular ceftriaxone for gonococcal

Question 22

List 5 common genital ulceration diseases?

Answer 22

• Herpes simplex
• Syphilis (Treponema pallidum)

Chancroid
Lymphogranuloma venereum (LGV)
Donovanosis

Question 23

Which serotype of HSV causes most genital ulceration?

Answer 23

HSV Type I (10%)

HSV Type II (90%)

Question 24

Morphology of Treponema pallidum?

Answer 24

Spirochete:

 Helical, slender, long cells

 Flagella within periplasm

Question 25

List the STDs causing multiple genital ulcers vs those causing single?

Answer 25

Single: Syphilis, LGV Multiple: Genital herpes, Chancroid, Donovanosis

Question 26

Ddx STDs causing genital ulcers based on lymph tenderness/ adenopathy?

Answer 26

Tender - Genital herpes, Chancroid, LGV Non-tender - Syphilis, Donovanosis

Question 27

Describe the edge, base and lymphadenopathy of genital ulcers by Herpes?

Answer 27

Edge: Soft (rim of inflammation) Base: Clean Lymphadenopathy: tender

Question 28

Describe the edge, base and lymphadenopathy of genital ulcers by Syhilis?

Answer 28

Edge: Indurated (elevated) Base: Clean Lymphadenopathy: Indolent

Question 29

Describe the edge, base and lymphadenopathy of genital ulcers by Chancroid?

Answer 29

Edge: Soft Base: Dirty, Gray Lymphadenopahty: tender

Question 30

Describe the edge, base and lymphadenopathy of genital ulcers by Donovanosis?

Answer 30

Edge: Serpinginous (wavy), white Base: BEEFY RED** granulation tissue Lymphadenopahty: Erosive lesion over nodes

Question 31

Describe the edge, base and lymphadenopathy of genital ulcers by LGV

Answer 31

Edge: soft Base: eroded papule Lymphadenopahty: PROMINENT* tender

Question 32

Lab Dx tests of Herpes?

Answer 32

TZANCK SMEAR: identify multinucleated giant cells via Wright or Giemsa stain Viral culture

Question 33

Describe how herpes can cause recurrent infection?

Answer 33

Mucocutaneous infection >> spread to local sensory nerve endings >> Maintain neuronal latency >> Reactivation and distal spread again

Question 34

Lab dx test for Syphilis?

Answer 34

Serology- detect specific antibodies: 1) Non-trepenamal specific test: Time-specific: VDRL, RPR tests 2) Treponemal specific tests: syphilis specific: TPPA, FTA-abs, EIA-syphilis test Need both for Dx**

Question 35

Antibody detection can Dx syphilis as soon as genitla ulcerations appear. T or F? *exam*

Answer 35

False Ulceration/ primary syphilis may appear before development of detectable antibodies

Question 36

Describe the time course of syphilis infection? *exam*

Answer 36

[Early syphilis (<2 years)] Infection >> primary syphilis (9-90 days) >> secondary s. (6 weeks to 6m) >> Early latent up to 2 years [Late syphilis (>2 years)] >> Late latent (3 to 30 years)**

Question 37

Disease outcome of syphilis?

Answer 37

 1/3: spontaneous cure  1/3: persistent latent  1/3: tertiary syphilis Infectivity decrease rapidly with time

Question 38

Describe the pathological damage caused by primary and secondary syphilis?

Answer 38

Primary = Local multiplication > ulceration > healing Secondary = Bloodstream dissemination > Localized at BV > lesion in skin, mucosa, LN, CNS

Question 39

Which organs are involved in latent syphilis?

Answer 39

spleen, lymph nodes

Question 40

How to clinically Dx Chancroid? Treatment?

Answer 40

- P/E: tenderness, ulceration, base, edge...etc - Due to unreliable culture: Dx if no evidence of syphilis and HSV –single dose of azithromycin or single dose Ceftriaxone

Question 41

Treatment options for genital ulceration?

Answer 41

Single dose azithromycin + single dose Ceftriaxone covers Gonorrhoea, Chlamydia trachomatis, Chancroid *Must always consider asymptomatic syphilis or HIV*

Question 42

How to Dx Genital lumps?

Answer 42

- No culture - No routine serology tests: only test if high-risk HPV suspected - Dx based on exam and clinical presentation **

Question 43

Causative pathogen of genital lumps?

Answer 43

Human papilloma virus (HPV): > 100 types causing genital warts

Question 44

Which serotypes of HPV mainly cause mucotaneous diseases at genitals?

Answer 44

* Genital warts = 6, 11 *** | * Laryngeal papillomata = 6, 11 •Oral papillomata = 6, 11, 16, 18,

Question 45

Incubation period of HPV and disease course?

Answer 45

Incubation period 1 to 6 month Most HPV infections are selflimited and are asymptomatic

Question 46

Clinical presentation of genital lumps caused by HPV?

Answer 46

Superficial, clusters of warts with grey appearance on the penis, vulva & perianal regions.

Question 47

Which HPV serotypes should be screened by serology?

Answer 47

HPV types associated with cervical cancer (esp. 16 & 18)