Correct Answer: C. MRSA
Contact-based isolation is the primary infection control measure for MRSA (Methicillin-Resistant Staphylococcus aureus) because transmission occurs through direct contact with colonized or infected body surfaces, contaminated hands, or fomites. MRSA is a nosocomial pathogen endemic in Indian hospitals, particularly in ICUs, surgical wards, and burn units. The organism survives on environmental surfaces and healthcare worker hands for extended periods, making hand hygiene and barrier precautions (gloves, gowns, dedicated equipment) essential. Contact precautions prevent horizontal transmission to other patients and healthcare workers. Unlike respiratory pathogens, MRSA does not spread through airborne or droplet routes under normal circumstances—it requires direct contact with the wound, skin, or mucous membrane. Indian hospital infection control guidelines (AIIMS, NIMS protocols) mandate contact isolation for all MRSA-positive patients, especially those with open wounds, catheter sites, or respiratory tract colonization. This is distinct from standard precautions and is implemented when MRSA is confirmed or suspected in high-risk patients.
Why the other options are wrong
A. Diphtheria — Diphtheria is a respiratory droplet-transmitted disease caused by Corynebacterium diphtheriae. It requires droplet precautions (not contact isolation) for the first 24 hours of effective antibiotic therapy. The toxin-mediated systemic manifestations (pseudomembrane, myocarditis, neuropathy) are not spread by contact with skin or fomites. NBE trap: students confuse diphtheria's cutaneous form with contact spread, but even cutaneous diphtheria is managed with standard precautions once antibiotics are started. B. Mumps — Mumps is a respiratory droplet-transmitted viral infection (paramyxovirus) spread via saliva droplets during coughing/sneezing. It requires droplet precautions, not contact isolation. The parotitis and meningitis are systemic manifestations of viral replication, not contact-based transmission. NBE trap: students may conflate all infectious diseases with contact precautions, but mumps is specifically a droplet-spread illness managed with droplet isolation for 5 days after symptom onset. D. Asthma — Asthma is a non-infectious chronic inflammatory airway disease, not a communicable disease requiring any isolation precautions. It is triggered by allergens, exercise, cold air, or viral infections but does not transmit from person to person. Including asthma is a clear distractor to test whether students understand that isolation precautions apply only to infectious agents. This is a fundamental concept trap in infection control.
High-Yield Facts
- Contact isolation is mandated for MRSA because transmission occurs via direct contact with colonized skin/wounds or contaminated fomites, not respiratory droplets.
- MRSA prevalence in India is highest in tertiary care ICUs (15–40%) and burn units; endemic in most Indian hospitals, making it a major nosocomial threat.
- Diphtheria requires droplet precautions (not contact), effective for 24 hours post-antibiotic initiation; cutaneous diphtheria needs standard precautions only.
- Mumps is droplet-transmitted (paramyxovirus); droplet precautions for 5 days from symptom onset; contact isolation is not indicated.
- Standard precautions (hand hygiene, PPE) apply to all patients; contact precautions are added when MRSA is confirmed or epidemiologically linked.
Mnemonics
MRSA Isolation = Contact (C = Contact, M = MRSA) MRSA → Contact precautions (skin/wound contact, fomites). Remember: Contact = MRSA. Diphtheria & Mumps = Droplet (D = Droplet). Isolation Precautions: RDC Rule Respiratory (TB, measles) → Airborne. Droplet (Diphtheria, Mumps, Meningococcemia) → Droplet. Contact (MRSA, VRE, C. difficile, Scabies) → Contact. Use when route of transmission is known.
NBE Trap
NBE pairs MRSA with respiratory diseases (diphtheria, mumps) to test whether students conflate "serious infection" with "contact transmission." The trap is assuming all hospital-acquired infections require contact isolation—in reality, transmission route (contact vs. droplet vs. airborne) determines precaution type.
Clinical Pearl
In Indian ICUs, MRSA colonization is often asymptomatic; a single patient can seed an entire ward through contaminated hands of healthcare workers. Contact precautions (gloves, gowns, hand hygiene) are non-negotiable in resource-limited settings where MRSA prevalence is high and antibiotic options are limited. Screening high-risk patients (post-surgical, catheterized, immunocompromised) on admission is standard practice in tertiary care hospitals.
_Reference: Jawetz, Melnick & Adelberg's Medical Microbiology (Ch. 15: Staphylococcus); Park's Textbook of Preventive and Social Medicine (Ch. 7: Communicable Diseases & Isolation Precautions); CDC/Indian Hospital Infection Control Guidelines_