L36 - Sexually transmitted diseases Flashcards
Define the reservoir, site of entry and transmission of STDs?
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)
Define the public health centers for STD?
Department of health Social hygiene clinics
Most common STI in HK?
Non-gonococcal urethritis/ nonspecific genital infection by Chlamydia trachomatis
3 typical clinical presentation features of STDs?
- Urethral discharge (urethritis/male).
- Genital ulcer (male and female)
- Genital lumps (male/female)
List 2 main pathogens that cause urethral discharge/ urethritis?
- Neisseria gonorrhoeae
- Chlamydia trachomatis
(Asymptomatic: Ureaplasma urealyticum, Mycoplasma genitalium)
(Rare: Herpes Simplex virus, Trichomonas vaginalis, yeasts)
Compare gonococcal and Non-gonococcal urethritis: onset, incubation period, relapse?
Gonococcal:
- 2-5 days
- Abrupt onset
- Rare relapse
Non-gonococcal:
- 7-14 days
- Gradual onset
- Common relapse
Compare gonococcal and Non-gonococcal urethritis: dysuria, discharge?
Gonococcal:
- Prominent dysuria
- Copious discharge
Non-gonococcal:
- Mild dysuria
- Scanty, non-purulent discharge
List infections caused by Chlamydia trachomatis serotype A,B,C?
Trachoma
List infections caused by Chlamydia trachomatis serotype D to K?
Cervicitis, urethritis, pelvic inflammatory disease, neonatal pneumonia
List infections caused by Chlamydia trachomatis serotype L?
Lymphogranuloma venereum (LGV)
List infections caused by Chlamydophila/ Chlamydia pneumoniae?
Respiratory tract infection (not genital)
How to clinically establish presence of urethritis?
- P/E
- Microscopy: swab for anterior surface of urethra, anal mucosa, endocervix:
- 1st swab for Gonococcal culture
- 2nd swab for Chlamydia culture
Which serotypes of chlamydia cause STDs?
D to L
Define the medium and culture for gonococcal urethritis?
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
Define the medium and culture for Chlamydial urethritis?
- Need special transport medium and cell culture: McCoy Cell Line shows Chlamydia inclusion bodies
- Can refrigerate for 24h
Name one test for rapid chlamydia urethritis Dx and give 2 limitations?
Antigen detection e.g. Chlamydiazyme
–Less sensitive than culture
–False-positive results from cross reacting bacterial species
Describe the morphology of gonococci and gram stain?
Gram-negative diplococci
small mucoid colonies
Pharyngeal gonorrhoea is often asymptomatic in normal adults. T or F?
True
Name one test for pharyngeal gonorrhea?
Direct fluorescent antibody (DFA) for gonococcal pharyngitis
Name one test for detecting both gonococcal and chlamydial urethritis simultaneously? Give 2 advantages?
nucleic acid amplification tests (NAAT): e.g. PCR
Higher sensitivity than culture
Performed on non-invasive specimens (e.g. first-void urine)
Treatment for urethritis?
- Single dose oral azithromycin/ 7 days oral doxycycline for chlamydial
- Single dose intramuscular ceftriaxone for gonococcal
List 5 common genital ulceration diseases?
- Herpes simplex
- Syphilis (Treponema pallidum)
Chancroid
Lymphogranuloma venereum (LGV)
Donovanosis
Which serotype of HSV causes most genital ulceration?
HSV Type I (10%)
HSV Type II (90%)
Morphology of Treponema pallidum?
Spirochete:
Helical, slender, long cells
Flagella within periplasm
List the STDs causing multiple genital ulcers vs those causing single?
Single: Syphilis, LGV
Multiple: Genital herpes, Chancroid, Donovanosis
Ddx STDs causing genital ulcers based on lymph tenderness/ adenopathy?
Tender - Genital herpes, Chancroid, LGV
Non-tender - Syphilis, Donovanosis
Describe the edge, base and lymphadenopathy of genital ulcers by Herpes?
Edge: Soft (rim of inflammation)
Base: Clean
Lymphadenopathy: tender
Describe the edge, base and lymphadenopathy of genital ulcers by Syhilis?
Edge: Indurated (elevated)
Base: Clean
Lymphadenopathy: Indolent
Describe the edge, base and lymphadenopathy of genital ulcers by Chancroid?
Edge: Soft
Base: Dirty, Gray
Lymphadenopahty: tender
Describe the edge, base and lymphadenopathy of genital ulcers by Donovanosis?
Edge: Serpinginous (wavy), white
Base: BEEFY RED** granulation tissue
Lymphadenopahty: Erosive lesion over nodes
Describe the edge, base and lymphadenopathy of genital ulcers by LGV
Edge: soft
Base: eroded papule
Lymphadenopahty: PROMINENT* tender
Lab Dx tests of Herpes?
TZANCK SMEAR: identify multinucleated giant cells via Wright or Giemsa stain
Viral culture
Describe how herpes can cause recurrent infection?
Mucocutaneous infection
» spread to local sensory nerve endings
» Maintain neuronal latency
» Reactivation and distal spread again
Lab dx test for Syphilis?
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**
Antibody detection can Dx syphilis as soon as genitla ulcerations appear. T or F? exam
False
Ulceration/ primary syphilis may appear before development of detectable antibodies
Describe the time course of syphilis infection? exam
[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)**
Disease outcome of syphilis?
1/3: spontaneous cure
1/3: persistent latent
1/3: tertiary syphilis
Infectivity decrease rapidly with time
Describe the pathological damage caused by primary and secondary syphilis?
Primary = Local multiplication > ulceration > healing
Secondary = Bloodstream dissemination > Localized at BV > lesion in skin, mucosa, LN, CNS
Which organs are involved in latent syphilis?
spleen, lymph nodes
How to clinically Dx Chancroid? Treatment?
- 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
Treatment options for genital ulceration?
Single dose azithromycin + single dose Ceftriaxone
covers Gonorrhoea, Chlamydia trachomatis, Chancroid
Must always consider asymptomatic syphilis or HIV
How to Dx Genital lumps?
- No culture
- No routine serology tests: only test if high-risk HPV suspected
- Dx based on exam and clinical presentation **
Causative pathogen of genital lumps?
Human papilloma virus (HPV): > 100 types
causing genital warts
Which serotypes of HPV mainly cause mucotaneous diseases at genitals?
- Genital warts = 6, 11 ***
* Laryngeal papillomata = 6, 11 •Oral papillomata = 6, 11, 16, 18,
Incubation period of HPV and disease course?
Incubation period 1 to 6 month
Most HPV infections are selflimited and are asymptomatic
Clinical presentation of genital lumps caused by HPV?
Superficial, clusters of warts with grey appearance
on the penis, vulva & perianal regions.
Which HPV serotypes should be screened by serology?
HPV types associated with cervical cancer (esp. 16 & 18)
