ic18 STI Flashcards by Nathaniel Chan

Out of Gonorrhea, Chlamydia, Syphilis, Genital Herpes, which are caused by bacteria or virus?

and what bacteria / virus?

Bacteria
Gonorrhea: Neisseria Gonorrhoeae
Chlamydia: Chlamydia Trachomatis
Syphilis: Treponema Pallidum

Virus
Herpes: HSV-2

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name 1 STI caused by fungi and 1 caused by parasites

vaginal candidiasis (candida albicans)
scabies (sarcoptes scabiei)

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What tests to diagnose Gonorrhea?

What symptoms are there (3 points)

Gram stain, Culture, NAAT (nucleic acid amplification test)

Purulent urethral discharge / Mucopurulent vaginal discharge
Dysuria
Urinary frequency

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Treatment for Gonorrhea

2nd line for Gonorrhea

Should treat for Chlamydia at the same time
First line
IM Ceftriaxone 500mg single dose
+
Chlamydia
PO Doxycycline 100mg BD for 7 days

(2nd line)
AG240
PO Azithromycin 2g single dose + IM Gentamicin 240mg single dose
+
Chlamydia treatment
PO Doxycycline 100mg BD for 7 days

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General management of sex partners

Should treat sex partners of past 60 days

If single dose, abstain from sexual activities for 7 days after treatment

If 7 day course eg. Doxycycline, abstain until finish 7 day course

Abstain until all sexual partners have been treated

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What causes Chlamydia?

How to diagnose Chlamydia

Chlamydia Trachomatis

NAAT

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Treatment for Chlamydia

What if first line is not available?

DAL7

PO Doxycycline 100mg BD for 7 days

PO Azithromycin 1g single dose
OR
PO Levofloxacin 500mg OD for 7 days

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What bacteria causes Syphilis?

How to diagnose Syphilis?

Treponema pallidum

Darkfield microscopy of exudate
Treponemal test
Non-treponemal test

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General idea of Treponemal and Non-treponemal tests

Using treponemal / nontreponemal antigen to detect antibodies

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What is Treponemal test be used for?
Isit used to confirm diagnosis or response to treatment? Why?

Used to confirm diagnosis

Not used for monitoring response to treatment as it can remain active for life

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What is the antigen used in non-treponemal test

General idea of non-treponemal test?

Cardiolipin

To produce the most dilute serum concentration with a positive reaction eg. 1:16 positive means 1:32 is negative

Declines after treatment, hence is used to measure response to therapy

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What is non-treponemal test used to monitor

Which is a better result, 1:8 or 1:32?

Used as a tool to monitor response to treatment

We will want a less dilute antibody titre
1:8 is better than 1:32 as it means that I dont have as much antibodies in the blood, hence need a higher concentration to detect enough antibodies

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Main difference between the use of Treponemal test and Non-treponemal test

Treponemal test can stay (+) for life, hence is used to confirm diagnosis only

Non-treponemal test will decline over time, hence is used to monitor response to treatment

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Treatment for Syphilis for Primary, Secondary or Early latent infection (<1 year duration)

IM Benzathine Pen G 2.4m units for 1 dose
(Pen allergy) PO Doxycycline 100mg BD x 14 days

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Treatment for Syphilis for Late latent (> 1 year), Tertiary, or Unknown duration

IM Benzathine Pen G 2.4m units once a week for 3 doses
(Pen allergy) Doxycycline 100mg BD x 28 days

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Treatment for Neurosyphilis

[Always treat for 10-14 days]
IV Crystalline Pen G 3-4m units Q4H

IM Procaine Pen G 2.4m units + PO Probenecid 500mg QD

(Pen allergy) IV / IM Ceftriaxone 2g

Monitoring for therapeutic response for syphilis

Neurosyphilis: use CSF fluid
The rest (primary, secondary, latent): Use blood

Monitor at 6, 12, 24 months
Treatment success = Decrease of antibody titre by at least 4x (1:64 to 1:16)

5 stages of HSV infection

Primary mucocutaneous infection
Infection of nerve ganglia
Latency
Reactivation
Recurrent outbreak / flares

Transmission of Genital herpes

Bodily fluids and skin to skin contact

Viral shedding from epithelial cells can occur → Transmissible even when asymptomatic

Symptoms of genital herpes (in infection and prodromal stage)

Painful vesicles
Ulcerative lesions
Local itching, pain, tender inguinal lymphadenopathy
Flu-like symptoms during first days of lesions

Prodromal symptoms (occur before reactivation)
Mild burning
Itching, tingling
Symptoms less severe in recurrent disease

How to diagnose Genital Herpes?

Virologic tests and Serologic tests

Virologic tests: Viral cell culture and NAAT

Serologic tests: HSV-1 and HSV-2 specific antibodies
Antibodies persists forever

Why should serologic tests not be done for the first episode of genital herpes?

What does presence of HSV-2 antibodies confirm?

Antibody takes 6-8 weeks to be detected

Anogenital infection

Non pharm management for genital herpes (4 points)

Warm saline bath to relieve discomfort
Analgesic, Anti-itch
Good genital hygiene
Counselling of shedding virus when asymptomatic, reactivation, triggers

What is the MOA of Acyclovir?

Inhibit DNA polymerase, inhibit DNA synthesis and replication

What are the 2 drugs for genital herpes and doses? Counselling point

Acyclovir PO 400mg TDS for 7-10 days (for severe disease or complications that req hospitalisation) IV 5-10mg/kg **TDS** x 2-7 days + Oral until treat for 10 days Valacyclovir (Valtrex) PO 1g **BD** for 7-10 days Counselling point: Drink enough water to prevent crystallisation in renal tubules

What are the 2 ways to reduce recurrent herpes flares Advantages of one over the other

Chronic suppressive therapy: can reduce frequency of occurrences decrease risk of transmission Episodic therapy: less costly, better compliance but need to start within 1 day of lesion outbreak does not reduce risk of transmission

Dose for Chronic suppressive therapy

42 5111 PO Acyclovir 400mg BD PO Valacyclovir 500mg OD (at least 10 episodes per year) PO Valacyclovir 1g OD

Dose for episodic therapy

(Acyclovir dose will be 2x higher than in chronic suppressive therapy) 2532 PO Acyclovir **800mg** BD x 5 days OR TDS for 2 days 23115 PO Valacyclovir 500mg BD for 3 days OR 1g OD for 5 days

Which STI can be passed through skin to skin contact?

Only Genital Herpes hence can have viral shedding even though asymptomatic! The rest are all mother to child, bodily fluids

Which infections can diagnose using NAAT? Which cannot?

Can: Gonorrhea Chlamydia Genital herpes Cannot: Syphilis

When is Ceftriaxone used in STI?

1) First line for gonorrhea (IM 500mg single dose) 2) Neurosyphilis (if pt has pen allergy, IV / IM 2g daily x 10-14 days

When is Doxycycline used for STI?

1) 1st line for Chlamydia 2) Syphilis, if patient has penicillin allergy, for primary / secondary / early latent → 14 days or late latent / unknown duration / tertiary → 28 days (basically not neurosyphilis can alr)

When is Azithromycin used in STI?

1) Chlamydia 2nd line (PO 1g single dose) 2) 2nd line for Gonorrhea (PO 2g single dose, taken with Gentamicin IM 240mg single dose)

What is considered treatment failure in Syphilis?

at 6 months Still showing signs and symptoms of disease Failure to get 4 fold decrease of antibody titre eg. 1:64 -> 1:16, or antibody titre increased Could be due to undetected neurosyphilis