Master Microbiology
for FMGE

What the FMGE Tests in Microbiology

The FMGE Microbiology section tests the candidate's ability to apply microbiological principles to clinical scenarios, focusing on the identification of pathogens, selection of appropriate diagnostic tests, interpretation of results, and choice of antimicrobial therapy. Emphasis is placed on common and clinically significant infections in the Indian subcontinent, including tuberculosis, enteric fever, malaria, hepatitis, HIV, and hospital-acquired infections. Candidates must demonstrate knowledge of specimen collection, staining techniques (Gram, ZN, Giemsa), culture media, and antibiotic sensitivity patterns. The exam also covers infection control measures, sterilization and disinfection, and immunization schedules. Questions often present a patient with specific signs, symptoms, and risk factors, requiring the candidate to deduce the most likely causative organism, the best diagnostic test, or the first-line treatment based on local resistance patterns.

High-Yield Concepts

• Gram-Positive Cocci: Staphylococcus aureus: Causes boils, carbuncles, osteomyelitis, and toxic shock syndrome. Diagnosis: catalase-positive, coagulase-positive. MRSA: treat with vancomycin (15-20 mg/kg IV q12h). For MSSA, use cloxacillin or cefazolin. Remember: S. aureus is a major cause of hospital-acquired pneumonia and surgical site infections.
• Gram-Negative Bacilli: Salmonella Typhi: Causes enteric fever with step-ladder fever, relative bradycardia, and rose spots. Diagnosis: blood culture in first week, Widal test (O titre ≥1:160, H titre ≥1:160) after week 1. First-line treatment: azithromycin (1g PO once daily for 7 days) or ceftriaxone (2g IV daily for 14 days). Increasing resistance to fluoroquinolones.
• Mycobacterium Tuberculosis: Causes pulmonary TB with cough >3 weeks, hemoptysis, night sweats, weight loss. Diagnosis: sputum smear for acid-fast bacilli (AFB) using Ziehl-Neelsen stain (≥3 samples), GeneXpert MTB/RIF for rifampicin resistance. First-line: 2 months of isoniazid, rifampicin, pyrazinamide, ethambutol (HRZE) followed by 4 months of HR. Directly Observed Therapy (DOTS) is standard.
• Plasmodium Species: Malaria: P. falciparum causes severe malaria with cerebral involvement, hypoglycemia, and acute kidney injury. Diagnosis: Giemsa-stained thick and thin blood films (parasitemia >5% is severe). Treatment: artesunate (2.4 mg/kg IV at 0, 12, 24h then daily) for severe malaria; for uncomplicated P. falciparum, artemether-lumefantrine (Coartem) for 3 days. P. vivax: chloroquine (25 mg/kg over 3 days) plus primaquine (0.25 mg/kg/day for 14 days) to prevent relapse.
• Hepatitis B Virus (HBV): Transmitted via blood, sexual contact, and perinatally. Serology: HBsAg positive indicates acute or chronic infection; HBeAg positive indicates high viral replication; anti-HBc IgM indicates recent infection. Chronic HBV: treat with tenofovir (300mg PO daily) or entecavir (0.5mg PO daily). Vaccination: 3-dose series at 0, 1, 6 months.
• HIV: Diagnosis and Management: Diagnosis: fourth-generation ELISA (p24 antigen + HIV antibodies) positive, confirmed by Western blot or HIV RNA. CD4 count <200 cells/μL defines AIDS. ART: tenofovir/emtricitabine (Truvada) plus dolutegravir (50mg PO daily) as first-line. Opportunistic infections: PCP prophylaxis (trimethoprim-sulfamethoxazole 1 DS tab daily) when CD4 <200; TB prophylaxis (isoniazid 300mg daily for 6 months) when CD4 <350.
• Clostridium Tetani: Tetanus: Causes generalized tetanus with trismus, risus sardonicus, opisthotonos. Diagnosis: clinical. Treatment: human tetanus immunoglobulin (3000-6000 IU IM), metronidazole (500mg IV q6h for 7-10 days), wound debridement, and diazepam for muscle spasms. Prevention: DPT vaccine (2,4,6 months) and booster every 10 years.
• Sterilization and Disinfection: Autoclaving (121°C, 15 psi, 15-20 min) is the gold standard for sterilization. Ethylene oxide gas for heat-sensitive instruments. Glutaraldehyde (2%) is a high-level disinfectant for endoscopes (20-30 min). Chlorhexidine (0.5-4%) is an antiseptic for skin preparation. Spaulding classification: critical items (e.g., surgical instruments) must be sterilized; semi-critical (e.g., endoscopes) require high-level disinfection; non-critical (e.g., stethoscopes) need low-level disinfection.

Common Traps in Microbiology Questions

• Candidates often confuse the Widal test interpretation: a single high titre is not diagnostic; a four-fold rise in paired sera is required.
• Many forget that for uncomplicated P. vivax malaria, primaquine is given to prevent relapse (hypnozoites), but it must be avoided in G6PD deficiency.
• A common mistake is treating viral hepatitis with antibiotics; hepatitis A and E are self-limiting and require supportive care only.
• Students frequently assume that a positive HBsAg always indicates chronic infection, but it can also be acute; anti-HBc IgM differentiates.
• In suspected TB, a negative sputum smear does not rule out TB; culture or GeneXpert is needed, especially in HIV co-infection.
• Candidates often forget that for tetanus prophylaxis in wound management, if the patient has had ≥3 doses of tetanus toxoid and the wound is clean, no immunoglobulin is needed; tetanus toxoid alone suffices.

How to Revise Microbiology for the FMGE

Focus on the most prevalent infections in India: tuberculosis, enteric fever, malaria, hepatitis, and HIV. Memorise the first-line treatments and resistance patterns, especially for TB (MDR-TB definitions) and malaria (artemisinin-based combination therapy). Practice interpreting serological panels (HBsAg, anti-HBc, HBeAg, anti-HIV, CD4 counts). For bacteriology, know the Gram stain and key biochemical tests (catalase, coagulase, oxidase, urease) for common organisms. Questions often present a clinical vignette with lab results; you must identify the organism and the next step in management. Spend time on sterilization methods and their indications, as direct questions appear. Use flashcards for organism-disease-treatment pairs. Review the National Immunization Schedule (India) for vaccines like BCG, OPV, IPV, DPT, and Hepatitis B.

Practise it: MedLumen has 50 Microbiology questions for the FMGE, each with a full explanation and references.