MRCP Part 1 Infectious Diseases: 50 Rapid-Review Facts

Crack Medicine
6 days ago
6 min read

TL;DR

This article provides mrcp part 1 infectious diseases: 50 rapid-review facts to sharpen your recall for the exam. You’ll also find high-yield sub-topics, a short case question, key traps and a practical checklist to integrate into your revision.

Why this matters

Infectious diseases remain a vital component of the MRCP Part 1 syllabus: you will be expected to recognise common pathogens, select appropriate investigations and first-line therapies, and avoid pitfalls around antimicrobial resistance and immunocompromised hosts. According to the official exam overview, the MRCP(UK) Part 1 “assesses the scientific and clinical knowledge … to a level appropriate for entry to specialist training.” Royal Colleges of Physicians UK+2RCP+2Effective revision in this domain can yield significant returns in terms of marks—and confidence. Use this article alongside our Free MRCP MCQs and mock tests at Crack Medicine to maximise your exam readiness.

Scope of Infectious Diseases in MRCP Part 1

The section covers microbial pathogens (bacteria, viruses, fungi, parasites), host-immune responses, infection control, antimicrobial therapy, and prophylaxis.
It is often integrated with microbiology, pharmacology and clinical medicine themes rather than appearing as standalone “ID only” questions. BMJ+1
The key skill tested is not just remembering names but applying them in clinical contexts: e.g., immunosuppressed patient presents with fever, choose likely organism and therapy.
As you revise, focus on high-yield topics (see next section), recognise common traps (later section) and consolidate knowledge into timed QBank practice and mock exams.

Five Most Tested Subtopics

Subtopic	Key Focus	Typical Question Format
HIV & opportunistic infections	CD4 count thresholds, prophylaxis, common OIs	“Which prophylaxis is indicated at CD4 <200?”
Tuberculosis (TB) including co-infection	Latent vs active TB, TB-HIV co-infection, extrapulmonary TB	“What is first-line regimen for TB meningitis?”
Sepsis, endocarditis & antimicrobial therapy	Empiric antibiotic choices, sepsis criteria, antibiotic side-effects	“Which drug is best empirically for suspected endocarditis in IV user?”
Viral hepatitis & chronic infections	Serology interpretation, management of HBV/HCV	“Which marker indicates high infectivity in HBV?”
Travel-related and tropical infections	Malaria, dengue, typhoid, travel history clues	“Returning traveller with fever + rash; likely diagnosis?”

50 Rapid-Review Facts

Here are selected high-yield facts you should recall readily in the final weeks of your revision.

In HIV infection, start antiretroviral therapy irrespective of CD4 count in most patients. World Health Organization+1
Pneumocystis jirovecii pneumonia (PCP) prophylaxis when CD4 <200/mm³: co-trimoxazole. Medscape Reference+1
Hepatitis B: HBeAg positivity implies higher infectivity.
Hepatitis C: no vaccine, but increasingly curable with direct-acting antivirals.
TB meningitis requires an extended regimen, often 12 months + adjunctive steroids.
Listeria monocytogenes – notable in neonates, elderly, immunocompromised; treated with ampicillin, not 3rd-generation cephalosporin.
Legionella pneumonia: look for hyponatraemia; treat with macrolide or fluoroquinolone.
Malaria diagnosis: thick and thin blood films remain gold standard.
Clostridioides difficile severe infection: first-line oral vancomycin rather than metronidazole.
Enteric (typhoid) fever: relative bradycardia, splenomegaly, rose-spots.
Epstein-Barr virus (EBV) mononucleosis: positive heterophile (Monospot) test; avoid amoxicillin due to characteristic rash.
Meningococcal septicaemia: non-blanching petechial rash, treat immediately with IV benzylpenicillin.
Leptospirosis (Weil’s disease): jaundice + renal failure + exposure to animal urine.
Brucellosis: undulant fever + exposure to unpasteurised milk.
Lyme disease: classic erythema migrans; treat early with doxycycline.
CMV in immunocompromised: retinitis (“floaters”), treat with ganciclovir/valganciclovir.
Herpes zoster: painful dermatomal vesicles; antivirals if within 72 h of onset.
Influenza: annual vaccination recommended for at-risk groups (NHS UK).
Tetanus: caused by Clostridium tetani; immunisation prevents disease, not necessarily colonisation.
Syphilis: painless chancre; VDRL may be negative early.
Gonorrhoea: treat with ceftriaxone IM plus test for chlamydia.
COVID-19: PCR remains gold standard; dexamethasone in severe disease (WHO guidance).
Infective endocarditis: apply Duke criteria; always obtain blood cultures before starting antibiotics unless extremely unstable.
Candidaemia: remove central venous line if possible; start echinocandin therapy.
Aspergillosis: radiological “halo sign” on CT chest; first-line voriconazole.
Histoplasmosis: can mimic TB in immunocompromised patients (especially travellers).
Cryptococcosis: India-ink stain positive in CSF; treat with amphotericin B + flucytosine.
Toxoplasmosis in AIDS: ring-enhancing brain lesions on MRI + positive IgG; treat with pyrimethamine + sulfadiazine.
Strongyloides: autoinfection potential, particularly when steroids given.
Schistosomiasis: haematuria in S. haematobium; treat with praziquantel.
Giardiasis: steatorrhoea in travellers; treat with metronidazole.
Botulism: Clostridium botulinum toxin causes descending flaccid paralysis; antitoxin required.
Mycoplasma pneumoniae: cold agglutinins positive; treat with macrolide.
Q fever: Coxiella burnetii; risk from livestock exposure.
Anthrax: cutaneous black eschar lesion; treat with ciprofloxacin if suspected.
Plague: Yersinia pestis; still exists in parts of Africa/Asia.
Leprosy (Hansen’s disease): skin lesions + peripheral neuropathy; Mycobacterium leprae.
MRSA (methicillin-resistant Staphylococcus aureus): treat with vancomycin or linezolid.
VRE (vancomycin-resistant enterococci): treat with linezolid or daptomycin.
Malaria prophylaxis: e.g., mefloquine weekly (avoid in epilepsy/psychiatric history).
Yellow fever vaccine: live attenuated; contraindicated in immunosuppressed.
Rabies: post-exposure prophylaxis essential before symptoms appear.
Dengue: thrombocytopenia, plasma leak; avoid NSAIDs.
Zika virus: microcephaly risk in neonates if maternal infection in pregnancy.
Ebola virus disease: high-mortality haemorrhagic fever; outbreak control and isolation key.
Norovirus: short incubation; frequent cruise-ship outbreaks.
Listeria (again) – important in pregnancy (neonatal sepsis) and immunosuppression.
Hantavirus: renal failure + pulmonary syndrome, exposure to rodent droppings.
Campylobacter jejuni: commonest bacterial gastroenteritis in the UK; may lead to Guillain-Barré syndrome.
Live vaccines in immunosuppressed: often contraindicated (e.g., MMR, varicella).

Doctor analyzing infectious disease cases with medical icons representing bacteria and viruses — concept for MRCP Part 1 infectious diseases topics.

Practical Example / Mini-Case

Case: A 35-year-old man on long-term corticosteroids for autoimmune disease presents with headache, fever and photophobia. CSF shows encapsulated yeast on India-ink stain. Question: What is the most likely pathogen and first-line treatment? Answer: The pathogen is Cryptococcus neoformans. First-line management is induction with liposomal amphotericin B plus flucytosine, followed by consolidation and maintenance with fluconazole. Rationale: Cryptococcal meningitis is a typical opportunistic infection in immunocompromised patients; recognising the India-ink stain and initiating correct therapy is a classic exam trap.

Study-Tip Checklist

☐ Review antibiotic and antifungal classes by mechanism, spectrum and major adverse effects.
☐ Use spaced-repetition flash-cards for HIV opportunistic infections and prophylaxis regimens.
☐ Memorise serology patterns for hepatitis B and C (surface antigen, e antigen, core IgM/IgG).
☐ Structure revision by pathogen type (virus, bacteria, fungus, parasite) and link to clinical syndrome.
☐ Attempt timed practice blocks from the MRCP Part 1 overview to build exam rhythm.
☐ Use the Free MRCP MCQs to self-test and identify weak areas.
☐ Review your analytics from mock tests weekly to pinpoint topic-drift and remediate.
☐ Maintain a “weird bug-drug” list (e.g., Listeria → ampicillin; Legionella → macrolide) for rapid recall under time pressure.

Common Pitfalls

Confusing bactericidal vs bacteriostatic therapy: you’ll be asked about “best empirical” rather than “which kills fastest”.
Ignoring side-effect questions (e.g., aminoglycosides → ototoxicity; linezolid → thrombocytopenia).
Overlooking co-infection clues (e.g., HIV + TB or HIV + cryptococcus) and thus selecting wrong therapy.
Neglecting to differentiate latent TB vs active TB regimens: always check for clinical disease signs.
Mis-interpreting serology panels in viral hepatitis: e.g., HBsAg vs anti-HBs vs IgM core antibody.
Overlearning ultra-rare infections while neglecting the “bread-and-butter” organisms that more commonly appear.

FAQs

Q1. How much infectious diseases content appears in MRCP Part 1?

While the exact number of questions varies, infectious diseases typically account for around 5-10% of the paper, often embedded within other systems.

Q2. Do I need to memorise precise antibiotic doses?

No. Exam focus is on class, mechanism, spectrum and contraindications rather than exact mg/kg dose.

Q3. What is the most efficient way to study Infectious Diseases for MRCP Part 1?

Combine concept-based learning (pathogens → syndrome → therapy) with active recall using QBank and timed mock passages to simulate exam conditions.

Q4. Are travel/tropical infections frequently tested?

Yes — illnesses such as malaria, dengue, typhoid and imported parasitic diseases appear regularly, especially with a travel-history stem.

Q5. Which resource should I begin with?

Start with the official MRCP(UK) Part 1 overview to understand format and domains, then move to question practice via our Free MRCP MCQs and full mock tests.

Ready to start?

You’re now equipped with 50 rapid-review facts and a structured checklist to boost your revision for infectious diseases in MRCP Part 1. Next step: begin practising on Crack Medicine’s Free MRCP MCQs. When you’re ready, take a full-length mock test under timed conditions to identify weak spots and refine your exam strategy. Good luck — you’ve got this.