MDRO
Formal Definition
A microorganism (bacteria or fungus) that is resistant to multiple classes of antimicrobial agents, typically defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories; common types include MRSA (methicillin-resistant Staphylococcus aureus), VRE (vancomycin-resistant Enterococcus), ESBL-producing Enterobacteriaceae (E. coli, Klebsiella), carbapenem-resistant Enterobacteriaceae (CRE), and C. auris; requires contact precautions in hospital and targeted antibiotic regimens based on susceptibility testing.
How It's Used on the Ward
"MDRO" — the patient is colonized or infected with a bacteria that s resistant to most of our usual antibiotics; we need to put them in contact isolation and choose our antibiotics very carefully based on the culture and sensitivity results; MRSA is the most common one to know.
Example
""68-year-old nursing home resident with recurrent UTIs, now presenting with dysuria and fever. Urine culture: Klebsiella pneumoniae resistant to ampicillin, ceftriaxone, ciprofloxacin, and piperacillin-tazobactam — susceptible only to meropenem and colistin. Diagnosis: ESBL-producing Klebsiella urinary tract infection (a multi-drug resistant organism). Started meropenem 1g IV q8h. Contact precautions initiated. Consult ID for colistin consideration if meropenem fails. Prior cultures show previous ESBL E. coli isolate — consistent with colonized patient with recurrent MDRO infections.""
Clinical Context
Types and definitions: MRSA = S. aureus resistant to oxacillin/nafcillin (and by implication all beta-lactams). VRE = Enterococcus faecalis/faecium resistant to vancomycin. ESBL = Enterobacteriaceae producing Extended-Spectrum Beta-Lactamase (resistant to all penicillins, cephalosporins, aztreonam). CRE = carbapenem-resistant Enterobacteriaceae (worst MDR Gram-negative — resistance to all beta-lactams including carbapenems; last resort = colistin, cefiderocol, or aztreonam). C. auris = multidrug-resistant yeast, spreads in healthcare settings, difficult to eradicate. Prevention: hand hygiene (alcohol-based is adequate for MRSA/VRE, need chlorhexidine for spores), contact precautions, antibiotic stewardship, chlorhexidine bathing in ICUs, dedicated cohorting of colonized patients. Decolonization: mupirocin for MRSA nares, chlorhexidine body washes for ICU patients.