MRSA & Multidrug-Resistant Organisms

A healthy college athlete shows up with what looks like a spider bite that's now a painful abscess — it's almost certainly not a spider.

Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to most traditional beta-lactam antibiotics (penicillins, most cephalosporins, carbapenems); ceftaroline is a notable beta-lactam with MRSA activity. MRSA exists in two epidemiologic forms. Community-acquired MRSA (CA-MRSA) causes skin and soft tissue infections in otherwise healthy people — abscesses, furuncles, and carbuncles, often mistaken for spider bites. Healthcare-associated MRSA (HA-MRSA) causes surgical site infections, ventilator-associated pneumonia, central line-associated bloodstream infections, and catheter-associated UTIs. Other key multidrug-resistant organisms: VRE (vancomycin-resistant Enterococcus) colonizes the GI tract and causes UTIs and bloodstream infections; CRE (carbapenem-resistant Enterobacterales) is associated with high mortality and extremely limited treatment options. All MDROs require contact precautions — gown and gloves for any patient interaction, dedicated equipment (stethoscope, blood pressure cuff), and private room or cohorting with same organism. MRSA treatment: CA-MRSA skin abscesses require incision and drainage (I&D) as primary treatment, with oral TMP-SMX or doxycycline if surrounding cellulitis is present. HA-MRSA systemic infections require IV vancomycin (monitor trough levels, target AUC/MIC guided dosing) or daptomycin or linezolid. Nasal decolonization with mupirocin ointment for MRSA carriers, especially pre-surgical patients. For purulent infections and abscesses, wound cultures should be obtained BEFORE starting antibiotics. Nursing: strict hand hygiene between all patient contacts, educate patients on wound care and avoiding sharing personal items (towels, razors), monitor vancomycin trough levels and renal function, and complete full antibiotic course education.

Key Distinctions

MRSA requires contact precautions, not droplet or airborne — students often over-isolate. CA-MRSA in a healthy person is primarily treated with I&D, not vancomycin — vancomycin is reserved for systemic HA-MRSA infections. Do not confuse MRSA nasal colonization (treated with mupirocin, no systemic antibiotics needed) with active MRSA infection. VRE is GI-colonizing and causes UTIs/bloodstream infections, while MRSA primarily affects skin and respiratory sites — different organisms, different clinical patterns, same contact precautions.

Clinical Pearl

Spider bite in a healthy person? Culture it — it's probably CA-MRSA. Drain first, antibiotics second.