Sexually Transmitted Diseases

Question 1

Definition

Answer 1

Infections that primarily transmit via sexual or related close bodily contact

Question 2

Treponema Pallidum recap: disease, clinical course, outcomes, treatment

Answer 2

Disease: Syphilis

• spirochetes
• non-cultivable in laboratory

Recap clinical course:

• 10-90 days: primary syphilis - painless genital ulcer (chancre)
• secondary syphilis - constitutional symptoms, rash, hepatitis, nephritis, uveitis etc. (widespread dissemination)
• latent syphilis (early = 1yr from contact; late = >1yr)

Outcome:

• remission (2/3)
• tertiary syphilis - CVS (aortitis>aortic aneurysm) and CNS morbidities (1/3)

Treatment:

• benzathine penicillin IM (1 dose if early latency, weekly x3 if late)
• doxycycline/erythromycin if allergy

Question 3

Treponema Pallidum Diagnosis

Answer 3

• dark ground microscopy - observe for motile spirochetes (false negatives as organism can’t survive long outside host; not routinely used as need dark field microscope)

Serous fluid from chancre:
Non-treponemal test (VDRL; venereal disease research laboratory): measure total IgM and IgG in titre
- SCREENING (non-specific)
- MONITORING treatment (quantitative)
- limitations: false +ve in pregnancy, rheumatoid factors, previous syphilis (need to rule out in Hx)

Treponemal test (TPPA or FTA-ABS)

• T. pallidum particle agglutination assay - qualitative test
• CONFIRMATORY (higher specificity) – rule out syphilis if -ve
• turns -ve after treatment (but not used as monitoring)
• limitation: cost

(CSF for neurosyphilis)

Question 4

Neisseria gonorrhoeae: gram’s stain, growth requirements, symptoms, diagnosis, treatment

Answer 4

Gram -ve diplococci
- attachment facilitated by pili to columnar epithelial cells

Delicate! - bedside inoculation onto chocolate agar, special transport medium and culture medium; extra CO2 requirement

Symptoms:

• Male: urethral discharge and dysuria
• Female: asymptomatic (endocervicitis)

Diagnosis:

• URETHRAL DISCHARGE for Gram’s STAIN AND CULTURE
• ENDOCERVICAL SWAB (columnar cells) for nucleic acid testing (not vaginal swab!)

Treatment:
- IM ceftriaxone
(add azithromycin if community-based)

Question 5

Chancroid: organism, gram’s stain, growth requirements, symptoms, diagnosis

Answer 5

Haemophilus ducreyi

• small gram negative bacilli
• requires special enriched medium and fresh preparation – difficult to culture
• found in Africa, SE Asia, developing countries

Symptoms:

• PAINFUL ulcer of genitalia (chancre)
• enlargement and suppuration of inguinal nodes

Enhances HIV transmission

Diagnosis:
- clinical

Question 6

Chlamydia trachomatis: serovars, symptoms, diagnosis, treatment

Answer 6

Obligate intracellular bacteria

• recall serovars A-C = trachoma
• D-K = mucosal diseases

Symptoms:

• male: NON-GONOCOCCAL URETHRITIS (urethral discharge)
• female: cervicitis, PID, peri-hepatitis
• newborn: inclusion conjunctivitis, pneumonia of newborns

Diagnosis;

• IMMUNOFLUORESCENCE staining of URETHRAL DISCHARGE
• Nucleic acid testing

Treatment:

• Azithromycin
• Doxycycline

Question 7

Newborn baby with sticky eyes DDx

Answer 7

Vaginal delivery acquired infection (mother usually asymptomatic)

GONOCOCCAL ophthalmia neonatorum
Neonatal CHLAMYDIA conjuncitivitis

Question 8

Lymphogranuloma venereum: cause, symptoms, diagnosis

Answer 8

Chlamydia trachomatis serovars L1-L3

• lymphoproliferative reaction and lymphangitis
• tropical and subtropical areas

Symptoms:

• painless, small ulcer
• inguinal nodes enlarged, painful and may rupture (bubo)

Diagnosis:

• usually clinical
• molecular testing available in reference lab only

Question 9

HSV genital infections: symptoms/ extra genital lesions, complications in pregnancy, diagnosis, treatment

Answer 9

HSV-2 mainly

Symptoms:

• genital lesions: cluster of painful ulcers and vesicular lesions on mucosa
• RECURRENCE is common (reactivation at localised site)
• neonatal disseminated herpes (primary herpetic encephalitis with high mortality)
• fluid from vesicles is infectious (autoinoculation e.g. herpes keratitis; extra genital lesions e.g. herpetic whitlow)
• facilitates HIV transmission

Diagnosis:

• VESICULAR FLUID for viral CULTURE/ PCR
• Ag detection (IF from skin scrapings)

Treatment:

• ORAL Acyclovir
• Suppressive therapy for recurrent infections

Question 10

Molluscum contagiosum: virus, transmission, spot diagnosis, outcome

Answer 10

Pox virus

• benign viral infections of the skin
• transmit by direct contact, fomites or sexual contact

Shining pearly white hemispherical umbilicated papule, enlarging slowly
- facial lesions seen in AIDS

Outcome:
- most cases self limiting in 6-9 months

Diagnosis:
- clinical (spot diagnosis)

Question 11

Human Papilloma Virus: transmission, symptoms, diagnosis, treatment

Answer 11

> 200 types transmitted through abrasion in skin, sexual contact

Tropism:

• cutaneous/ non-genital warts (plantar warts)
• anogenital warts (genital warts, cervical cancer) - HPV6/11

Diagnosis:
- clinical

Treatment:

• topical cream (imiquimod cream)
• ablation

Question 12

Vaginitis DDx

Answer 12

Candida albicans
Trichomonas vaginalis
Bacterial vaginosis

Question 13

Candida Vaginitis: transmission, at risk groups, symptoms, diagnosis, treatment

Answer 13

Candida albicans

NOT always sexually transmitted (most cases non-STI)
- pregnancy, antibiotics, immunosuppression, DM

Symptoms:
- PRURITUS vulvae, vaginal discharge
(vulvovaginitis, balanoposthitis in man)

Diagnosis:

• marked discharge “curd cheese” on bedside speculum exam
• vaginal swab for fungal culture if in doubt

Treatment:
- imidazoles pessary/ cream PV

Question 14

Trichomoniasis: organism, symptoms, diagnosis, treatment

Answer 14

Trichonomona vaginalis (flagellate protozoan)
- sexual transmission

Symptoms:

• male: mostly asymptomatic
• female: MALODOROUS vaginal discharge

Diagnosis:
- VAGINAL SWAB for CULTURE

Treatment:

• metronidazole (note DDI with COC)
• tinidazole

Question 15

Bacterial Vaginosis: organism, symptoms, diagnosis, treatment

Answer 15

POLYMICROBIAL
- imbalance and overgrowth of anaerobes e.g. peptostreptococcus; Gardnerella vaginalis (MC)

Symptoms:

• vaginal discharge
• “FISHY SMELL”

Diagnosis:
- VAGINAL SWAB for gram’s STAIN –> “CLUE CELL” (squamous epithelial cell packed with dense coccobacilli blurring edge of cell)

Treatment:
- metronidazole

Question 16

Arthropod infestation: Scabies - transmission, symptoms, sites, diagnosis

Answer 16

Sarcoptes scabiei (very common in HK)

• transmitted by close bodily contact, fomites
• Female mite - burrowing horny layer of skin to lay eggs

Symptoms:
- localised and generalised intense irritation and itchiness

Burrows: webs between fingers, lower buttock, penile shaft, scrotum

Diagnosis:

• clinical
• SKIN SCRAPINGS for lab demonstrations of mites or eggs

Question 17

Arthropod infestation: Pubic Lice - organism, transmission, symptoms, diagnosis

Answer 17

Pediculosis pubis

• Phthirus pubis (crab louse): legs with CLAWS suitable for gripping
• transmit by sexual contact, fomites

Symptoms:
- itchiness, “something crawling”

Diagnosis:
- demonstration of dark nits (eggs), white empty eggs, lice

Question 18

Antibiotic resistance of STD

Answer 18

Common! - always check guidelines for drug use

Question 19

Local epidemiology

Answer 19

2 new cases/day
Commonly sexually transmitted (MSM > heterosexual)

Most common Dx = Non-gonococcal urethritis