STI Guidelines 2026: Syphilis & Gonorrhea

TL;DR

For MRCP Part 1, sexually transmitted infections frequently appear in infectious disease questions, especially syphilis and gonorrhoea. The ID: STI Guidelines 2026: Syphilis & Gonorrhea topic focuses on recognising clinical stages, selecting appropriate diagnostic tests, and understanding guideline-based antibiotic therapy. This exam-focused guide summarises the most testable points, common pitfalls, and practical clinical scenarios aligned with modern STI management guidelines.

MRCP Part 1: STI Guidelines 2026 – Syphilis & Gonorrhea

Sexually transmitted infections (STIs) remain a high-yield topic in Infectious Diseases for MRCP Part 1. Among them, syphilis and gonorrhoea are frequently tested due to their characteristic clinical features, defined diagnostic algorithms, and evolving antimicrobial treatment strategies.

For candidates preparing for the exam, mastering these conditions requires understanding both classical clinical presentations and current guideline-based management.

If you are starting your preparation, review the MRCP Part 1 overview and reinforce knowledge through structured revision with Free MRCP MCQs and concept-based MRCP lectures.

Why this matters

In MRCP Part 1 examinations, infectious disease questions often test:

• Pattern recognition of clinical syndromes

• Interpretation of laboratory investigations

• Knowledge of first-line antimicrobial therapy

• Recognition of complications

Syphilis and gonorrhoea are ideal exam topics because they combine distinct clinical signs with clear diagnostic pathways.

Typical MRCP scenarios include:

• A painless genital ulcer with lymphadenopathy

• Rash involving palms and soles

• Urethral discharge with intracellular Gram-negative diplococci

• Treatment decisions based on antimicrobial resistance

Recognising these patterns quickly is crucial for answering exam questions accurately.

Core sections

1. Syphilis: Causative Organism and Transmission

Syphilis is caused by the spirochaete Treponema pallidum, transmitted primarily through sexual contact or vertical transmission during pregnancy.

Key epidemiological points:

• Increasing global incidence

• Higher prevalence among men who have sex with men (MSM)

• Frequent HIV coinfection

Exam pearls:

• Treponema pallidum cannot be visualised on standard Gram stain

• Diagnosis relies primarily on serological testing

2. Clinical Stages of Syphilis

The staging of syphilis is a classic MRCP exam topic.

Stage	Key Clinical Features	Timing
Primary	Painless chancre, regional lymphadenopathy	~3 weeks after exposure
Secondary	Rash (palms/soles), mucous patches, condylomata lata	Weeks to months
Latent	Asymptomatic with positive serology	Early or late
Tertiary	Neurosyphilis, cardiovascular syphilis, gummas	Years later

Important exam clue:

Maculopapular rash involving palms and soles strongly suggests secondary syphilis.

3. Diagnostic Testing for Syphilis

Two categories of serological tests are used.

Non-treponemal tests

• VDRL (Venereal Disease Research Laboratory test)

• RPR (Rapid Plasma Reagin)

Uses:

• Screening

• Monitoring treatment response

Treponemal tests

• TPPA (Treponema pallidum particle agglutination assay)

• FTA-ABS (Fluorescent treponemal antibody absorption)

• EIA (enzyme immunoassay)

Uses:

• Confirmatory diagnosis

Important MRCP concept:

Treponemal tests remain positive for life, while RPR or VDRL titres decline following successful treatment.

4. Treatment of Syphilis

First-line therapy remains benzathine penicillin G.

Stage	Treatment
Primary syphilis	Single dose IM benzathine penicillin
Secondary syphilis	Single dose IM benzathine penicillin
Early latent	Single dose
Late latent	Weekly doses for 3 weeks
Neurosyphilis	IV penicillin for 10–14 days

A well-known complication of treatment is the Jarisch–Herxheimer reaction.

Features include:

• Fever

• Myalgia

• Headache

• Temporary worsening of symptoms

This reaction occurs due to rapid destruction of spirochaetes and does not represent a penicillin allergy.

5. Gonorrhoea: Pathogen and Microbiology

Gonorrhoea is caused by Neisseria gonorrhoeae, a Gram-negative diplococcus.

Key microbiological characteristics:

• Oxidase positive

• Intracellular diplococci in neutrophils

• Ferments glucose but not maltose

Exam scenario:

Microscopy showing Gram-negative intracellular diplococci from urethral discharge.

6. Clinical Features of Gonorrhoea

Clinical presentation varies between men and women.

Men

• Dysuria

• Purulent urethral discharge

Women

• Cervicitis

• Pelvic inflammatory disease

Complications include:

• Epididymitis

• Infertility

• Disseminated gonococcal infection (DGI)

DGI classically presents with:

• Tenosynovitis

• Dermatitis

• Polyarthralgia

This triad is frequently tested in MRCP examinations.

7. Diagnosis of Gonorrhoea

The preferred diagnostic test is NAAT (nucleic acid amplification testing).

Samples may include:

• Urine

• Urethral swabs

• Cervical swabs

• Rectal or pharyngeal swabs

Culture is still important for detecting antibiotic resistance.

8. Current Treatment Recommendations

Due to rising antimicrobial resistance, most guidelines recommend ceftriaxone-based therapy.

Typical regimen:

• Single IM dose of ceftriaxone

If chlamydia coinfection is suspected:

• Doxycycline for 7 days

Important MRCP trap:

Fluoroquinolones are no longer recommended due to widespread resistance.

9. Key Differences Between Syphilis and Gonorrhoea

Feature	Syphilis	Gonorrhoea
Organism	Treponema pallidum	Neisseria gonorrhoeae
Ulcer	Painless chancre	Rare
Rash	Palms and soles	Uncommon
Diagnostic test	Serology	NAAT
First-line treatment	Penicillin	Ceftriaxone

10. Public Health and Screening

Modern STI guidelines emphasise:

• Partner notification

• Screening for other STIs including HIV

• Testing during pregnancy

Early detection prevents complications such as:

• Congenital syphilis

• Infertility

• Chronic pelvic inflammatory disease

For broader infectious disease revision, see this related guide: High-Yield Infectious Diseases for MRCP Part 1https://www.crackmedicine.com/blog/high-yield-infectious-diseases-for-mrcp-part-1

Practical examples / mini-cases

Clinical MCQ

A 30-year-old man presents with a painless genital ulcer and non-tender inguinal lymphadenopathy. Serology shows positive RPR and TPPA.

What is the most appropriate treatment?

A. Oral azithromycinB. Intramuscular benzathine penicillin GC. Oral doxycyclineD. Intravenous ceftriaxone

Correct answer: B — Intramuscular benzathine penicillin G

Explanation:

This presentation is consistent with primary syphilis, where the recommended treatment is single-dose intramuscular benzathine penicillin G.

Practical Study-Tip Checklist

Use this quick revision checklist before the exam:

1. Memorise syphilis stages and key clinical features

2. Understand treponemal vs non-treponemal tests

3. Learn first-line antibiotic regimens

4. Recognise Jarisch–Herxheimer reaction

5. Identify gonococcal resistance patterns

6. Remember disseminated gonococcal infection triad

7. Practise case-based questions regularly

You can test your knowledge using exam-style questions in the MRCP Qbank:https://www.crackmedicine.com/qbank/

Common pitfalls (5 bullets)

• Confusing painless syphilitic chancre with painful chancroid ulcers

• Assuming treponemal titres fall after treatment

• Forgetting Jarisch–Herxheimer reaction after therapy

• Treating gonorrhoea with fluoroquinolones despite resistance

• Missing disseminated gonococcal infection presenting with arthritis

FAQs

What is the first-line treatment for primary syphilis?

The standard treatment is intramuscular benzathine penicillin G as a single dose. This regimen is recommended by international STI guidelines.

How is gonorrhoea diagnosed today?

The preferred diagnostic test is NAAT (nucleic acid amplification testing) using urine or genital swabs. Culture may be used to monitor antibiotic resistance.

What causes the Jarisch–Herxheimer reaction?

This reaction occurs after starting treatment for syphilis and is caused by rapid destruction of spirochaetes, leading to a transient inflammatory response.

Why are fluoroquinolones no longer used for gonorrhoea?

Due to global antimicrobial resistance, fluoroquinolones are no longer recommended. Current guidelines favour ceftriaxone-based therapy.

Are STI questions common in MRCP Part 1?

Yes. Conditions such as syphilis, gonorrhoea, HIV infection, tuberculosis, and hepatitis frequently appear in MRCP Part 1 infectious disease questions.

Ready to start?

Effective preparation for MRCP Part 1 requires focused revision and repeated exposure to exam-style questions.

Start strengthening your infectious disease knowledge today:

• Review the MRCP Part 1 syllabus and overviewhttps://www.crackmedicine.com/mrcp-part-1/

• Practise high-yield exam questionshttps://www.crackmedicine.com/qbank/

• Learn complex topics with structured teachinghttps://www.crackmedicine.com/lectures/

Consistent revision with guideline-aligned material is one of the most reliable strategies for success in MRCP Part 1.

Sources

MRCP(UK) Examination Blueprinthttps://www.mrcpuk.org/mrcpuk-examinations/part-1

British Association for Sexual Health and HIV (BASHH) STI Guidelineshttps://www.bashhguidelines.org

CDC Sexually Transmitted Infection Treatment Guidelineshttps://www.cdc.gov/std/treatment-guidelines/default.htm

World Health Organization STI Guidelineshttps://www.who.int/publications/i/item/9789241549950