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ERS > ERS36 Sexually Transmitted Disease > Flashcards

ERS36 Sexually Transmitted Disease Flashcards

1
Q

STI

A

Definition: Disease transmitted by sexual contact

HIV, Syphilis may also be transmitted by blood transfusion / needle stick injury
- do not “travel alone” (may have >1 STD)
- many asymptomatic (act as reservoir for ongoing transmission)

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2
Q

Encounter + Entry of STI agents

A
  • NOT survive in environment (very sensitive to drying, disinfectant, heat)
  • NOT free-living —> Practically never found free in environment
  • NO animal reservoir
    —> cannot blame toilet seat / bath tub

Entry:
- Reservoir: asymptomatic human carrier (human-to-human transmission)
- Mucous membrane (Columnar epithelium) / Minute abrasions on skin (Squamous epithelium)
- Local sites (vagina, cervix, urethra, rectum, pharynx)
- Primary lesions at / near site of entry

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3
Q

Consequence / Complications of STI

A
  1. ***Pelvic inflammatory disease
    —> infertility, ectopic pregnancy
  2. Anogenital cancer (predisposed by HPV infection)
  3. Secondary / Tertiary syphilis
  4. Recurrent herpes infection
  5. Increase risk of HIV infection
  6. Adverse outcome of pregnancy
  7. Congenital diseases (e.g. Syphilis, Herpes) —> can be life-threatening to baby
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4
Q

Major STI in HK

A

Decreasing incidence:
1. Chlamydia trachomatis
- Non-gonococcal urethritis (NGU) —> Male
- Non-specific genital infection (NSGI) —> Female
2. Genital warts
3. Gonorrhoea
4. Syphilis
5. Genital herpes

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5
Q

***Clinical presentations of STD

A

Big 3:
1. Urethral discharge (Urethritis: Male)
2. Genital ulcer (Male / Female)
3. Genital lumps (Male / Female)

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6
Q
  1. Urethral discharge
A

Caused by Urethritis

Main causes:
1. **Neisseria gonorrhoea (GC) (淋病雙球菌)
2. **Chlamydia trachomatis (CT) (衣原體)

Other organisms (controversial) —> NOT generally work-up
3. Mycoplasma genitalium
4. Ureaplasma urealyticum
5. HSV (rare)
6. Trichomonas vaginalis (rare)
7. Yeasts (rare)

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7
Q

***Typical urethritis

A
  1. Gonorrhoea Urethritis (GU) (淋病/白濁)
    - Neisseria gonorrhoeae: Gram -ve diplococci
    - 2-5 days incubation
    - **Abrupt onset
    - **    Prominent dysuria
    - ***Copious, Milky discharge
    - Rare relapse
  2. Non-gonococcal urethritis (NGU) —> Chlamydia trachomatis
    - 7-14 days incubation
    - **Gradual onset
    - **    Mild dysuria
    - ***Little discharge
    - Common relapse
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8
Q

Management of urethritis

A
  1. Establish presence of urethritis
    - P/E + Microscopy (WBC, Bacteria)
  2. 2 approaches of treatment
    - 1. **Empirical treatment —> No work up in initial visit —> **cover both GC + CT
    - 2. Work up and treat
    —> depends on availability of tests, patients’ preference
  3. Evaluate + Treat partner appropriately
  4. Follow-up examination (optional)
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9
Q

Drug treatment for urethritis

A

Cover for both GC + CT:
**Ceftriaxone (single dose IM for **GC) + **Azithromycin (single dose for **CT) / Doxycycline (7 days for CT)

Tetracycline, Penicillin, Fluoroquinolone, oral Cephalosporin
—> Abandoned as 1st line for GC (∵ resistance common)
—> unless have culture / susceptibility results

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10
Q

Chlamydial infections

A

Family: Chlamydiaceae
Genus: Chlamydia

Obligate **Intracellular parasite
1. Chlamydia trachomatis
- A, B, C —> Trachoma (eye disease)
- **D to K —> Cervicitis, Urethritis, PID, Neonatal pneumonia
- ***L —> Lymphogranuloma venereum (LGV) (LN infection)

  1. Chlamydia pneumoniae —> Respiratory tract infection
  2. Chlamydia psittaci —> Psittacosis (respiratory tract)
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11
Q

Collection of sample from Penis, Anal canal, Cervix

A

Penis:
Insert specimen swab 0.5 - 1cm into urethra
—> rotate several times within urethra
—> transport in transport jelly
—> send for bacterial culture

Anal canal / Cervix:
Use larger specimen swabs

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12
Q

***2 swabs

A

1st one for GC culture, 2nd one for CT culture

  1. GC culture
    - GC dies quickly
    - **directly inoculate into agar palate at bedside (preferred)
    - Transport specimen in special transport tube / swab —> send to lab **    IMMEDIATELY (any delay compromise yield)
    - ***Never refrigerate specimen

Main test: Culture
- Must use nutritive culture media with antibiotics (to inhibit overgrowth of normal flora) (selective / differential medium)
—> Modified Thayer-Martin medium (exam: Selective medium for Neisseria gonorrhoeae) —> small, greyish-white to colour mucoid colonies
—> ***Martin-Lewis medium
- 35oC, CO2 enriched, humid

  1. CT culture
    - transport and storage requirement completely different
    - specimen **MUST be sent in special transport medium (X swab)
    - **    can be refrigerated (4oC) for up to 24 hrs if cannot deliver to lab immediately
  • 2 methods
    —> **Cell culture (e.g. **McCoy cell line) (∵ obligatory intracellular organism) —> **Cytopathic changes with **Inclusion bodies inside McCoy cells

—> Antigen detection (e.g. Chlamydiazyme)
- perform directly on clinical specimen
- rapid test result
- less sensitive than culture
- false positive results from cross reacting bacterial species

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13
Q

Pharyngeal gonorrhoea

A

AIDS / Immunocompromised: Gonococcal pharyngitis
Immunocompetent: Asymptomatic —> diagnostic difficulty

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14
Q

Alternative work-up approach

A

***Nucleic acid amplification tests (NAAR)
- PCR
- LCR (Ligase chain reaction)
- TMA (Transcription-mediated amplification)

Advantages:
- **Faster (~ hours) (∵ culture take a few days)
- **Detect both GC + CT in one specimen
- ***Higher sensitivity than culture —> reliable
- Can be performed on non-invasive specimens (e.g. urine, vulval swab) with good results
—> make screening people at risk acceptable

Limitations:
- ***Costs

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15
Q
  1. Genital ulcer (Male / Female)
A
  • Single / Multiple
  • With / without vesicles
  • Different forms
  1. ***Syphilis (梅毒)
  2. ***Herpes simplex (生殖器疱疹)
  3. Chancroid (軟性下疳)

(4. Lymphogranuloma venereum LGV (rare)
5. Donovanosis (rare): by Calymmatobacterium granulomatis)

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16
Q

Syphilis vs Herpes vs Chancroid vs LGV vs Donovanosis

A

Syphilis:
- **Clean base
- **Indurated (Hardened) elevated edge
- Not tender (Chancres)

Chancroid:
- **Dirty, gray base
- Soft edge
- **Marked tenderness

Herpes:
- **Multiple shallow ulcerations + vesicles
- **Erythematous rim

Donovanosis:
- ***Beefy red base
- Elevated
- Serpiginous (wavy) edge

LGV:
- ***Prominent lymphadenopathy / enlarged inguinal LN

(see table for more details)

17
Q

Approach for genital ulcerations

A

If Typical syndrome
—> Lab tests may not be necessary

If Lab service limited
—> syndromic management approach may be used

18
Q

***Genital herpes

A

Causative agent:
Herpes simplex viruses
- type 1 (10%): mouth
- ***type 2 (90%): genital strain

Gross:
***Ulcerating vesicles

Incubation period:
- 2-5 days

Diagnosis:
- based on clinical appearance

Laboratory diagnosis:
1. **Tzanck smear
- only positive in ~50% of cases
- smear obtained by scraping base of vesicle / ulcer with a scalpel
—> material then fixed in alcohol
—> stained with **Wright / Giemsa stain
—> ***Multinucleated giant cells (characteristic of Herpes infection (not necessarily simplex))

  1. ***Viral culture
    - days
    - positive up to 80% (depend on stage)
    - Cytopathic effect in cell line (A549 cell)
  2. Antibody test
    - no use in diagnosis
19
Q

Herpes infection

A
  • Can recur despite treatment
  • **NO antiviral can eliminate latency in neurons
    —> can **    only treat active lesions
    —> cannot prevent reactivation

Mucocutaneous infection
—> Spread to local sensory nerve endings
—> Establishment + Maintenance of neuronal latency in ***ganglion
—> Reactivation of virus + distal spread
—> Mucocutaneous infection recurrence

20
Q

***Syphilis

A

Causative agent:
**Treponema pallidum (a **spirochete 螺旋體)
- helical
- slender
- long cells
- flagella within periplasm

***NOT cultivable in artificial media

Pathogenesis:
- ***Multiply very slowly —> Long incubation period
- Enter body through minute abrasions

Primary syphilis —> ***local multiplication —> Ulceration (Chancre) / inflammation —> Healing spontaneously

Secondary syphilis —> **Bloodstream dissemination —> Organism localised around blood vessels —> **Lesions in skin, mucous membrane, LN, CNS etc. —> later ***Endarteritis (inflammation of the inner lining of an artery)

Latent syphilis —> Residual organism in ***Spleen / LN

Late syphilis —> Renewed multiplication of Residual organism —> take many years before patient present clinically —> ***damage to organ / tissue

21
Q

Natural history of Syphilis

A

***Infectivity ↓ rapidly with time (< 2 years highly infectious, > 2 years less infectious) —> 用2年做分界線

Early Syphilis (***< 2 years):
Infection (incubation period: 9-90 days)
—> Primary
(6 weeks-6 months)
—> Secondary
—> Early latent

Late Syphilis (***> 2 years):
(3-30 years)
—> Late latent
—> Spontaneous cure / Persistent latent / Tertiary syphilis (each 33%)

22
Q

***Microbiological diagnosis of Syphilis

A
  1. **Serology
    - Specific Ab detection
    - **    Mainstay approach
  2. Direct microscopy of ulcer exudate
    - NOT sensitive
    —> **Dark field microscopy (very tiny organism, 5-20 regular spirals rotation, undulation, compression, expansion)
    —> Immunofluorescence staining (not generally available)
    —> **    Cannot be visualised by Gram stain!!!
23
Q

***Serological diagnosis of Syphilis

A

Often take **>= 2-4 weeks for result to be positive (even weeks after initial symptoms)
—> **take long time for Ab to develop
—> Ab may still be lower than detection limit even symptoms appear

Non-treponemal specific tests (***L/R字尾)
1. VDRL test (venereal disease research laboratory)
2. RPR test (rapid plasma reagin)

Advantages:
- distinguish **Past / Inactive vs Untreated syphilis (∵ Ab level之後會降低)
- expressed in titre —> **Disease activity indicator

Disadvantages:
- Biological false-positive

Treponemal specific tests (***A字尾)
1. EIA-syphilis test (enzyme immunoassay)
2. TPPA test (treponema pallidum particle agglutination assay)
3. FTA-abs test (fluorescent treponemal antibody absorption)

Advantages:
- ***More specific

Disadvantage:
- unable to distinguish ***Past syphilis (treated) vs Untreated syphilis —> result remain positive for life (∵ Ab level唔會降低)

***Overall: Use combination of both Non-treponemal + Treponemal specific tests
—> Tests results also MUST be interpreted with patient history (∵ may have false-positive)

24
Q

Traditional screening algorithm

A

Non-treponemal specific test (e.g. RPR)
—> Reactive —> Treponemal test (e.g. FTA) —> Reactive —> Syphilis
—> Reactive —> Treponemal test (e.g. FTA) —> Non-reactive —> negative for Syphilis (i.e. Other agents)
—> Non-Reactive —> negative for Syphilis

25
Q

Reverse screening algorithm

A

Treponemal specific test (e.g. EIA)
—> Reactive —> Non-treponemal test (e.g. RPR) —> Reactive —> Syphilis
—> Reactive —> Non-treponemal test (e.g. RPR) —> Non-reactive —> confirm with ***2nd Treponemal specific test (e.g. TPPA) —> Reactive —> Syphilis (if Non-reactive: negative)
—> Non-Reactive —> negative for Syphilis

26
Q

Chancroid

A

***Rare in HK
caused by Bacteria

Empirical treatment:
- **Azithromycin single dose
- **Ceftriaxone single dose

Work up
1. Gram-smear —> **NOT reliable
2. **Culture —> e.g. **Hammond gonococcal medium —> can be problematic (many labs don’t have medium)
3. **Diagnosis presumed if no evidence of Syphilis / HSV

27
Q

Syndromic approach for Urethritis / Genital ulcer

A

Magic combination:
Azithromycin (single dose) + Ceftriaxone (single dose)

Cover:
1. GC
2. CT
3. Chancroid

Check:
- NOT Herpes **clinically
- Always consider Syphilis (no lesions, use **blood samples) and HIV (must obtain consent) ∵ asymptomatic

If above doesn’t work
—> Consider alternative diagnosis / Refer

28
Q

Why not just treat by clinical diagnosis / syndromic approach?

A

Single dose antibiotic high effective, few SE

HOWEVER, workup is important:
1. Medico-legal case (rape, sex abuse)
2. Epidemiology (baselines, outbreaks, strain typing)
3. Antibiotic susceptibility tests (if resistance high, may need to abandon existing 1st line agents)

29
Q
  1. Genital lumps (Male / Female)
A

Causative agent:
HPV (Human papilloma virus)
- >100 types
- all infect skin / mucosal surface
- >=40 infect genital area
- Warts: penis, vulva, perineal regions
- incubation period 1-6 months
- **most infection self-limited, asymptomatic —> unrecognised
- **Treatment: symptomatic —> removal of warts
- ***16, 18 esp. associated with Cervical cancer

Clinical presentation:
- Genital warts (椰菜花)

Diagnosis:
- ***Clinical diagnosis (unique enough)
- CANNOT be cultured
- NO routine serology tests available
- HPV tests available to detect Oncogenic types in context of Cervical cancer screening —> but NOT suitable as general STD test

30
Q

HPV types and diseases

A

NOT all sexually transmitted
***Molecular tests to distinguish between types

Skin disease
1. Plantar warts (1, 4)
2. Common warts (2, 4, 7)
3. Flat warts (3, 10)

Mucocutaneous disease
1. Genital warts **(6, 11)
2. Laryngeal papillomata **(6, 11)
3. Oral papillomata (2, **6, **11, **16, **18, 57)

31
Q

***Summary

A

Urethral discharge:
1. Gonorrhoea Urethritis (淋病/白濁)
2. Non-gonococcal urethritis (NGU) —> Chlamydia trachomatis (衣原體)

Genital ulcers:
1. Syphilis (梅毒)
2. Herpes simplex (生殖器疱疹)
3. Chancroid (軟性下疳)

Genital lumps:
1. HPV (6, 11, 16, 18)

ERS (41 decks)

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