Antimicrobial Stewardship and Multidrug-Resistant Organism Control
Antimicrobial stewardship and MDRO control questions test core elements, metrics, and the link between antibiotic use and resistance. Expect de-escalation, time-outs, antibiograms, restricted agents, and MDRO transmission control.
Core rules
- CDC Core Elements: leadership commitment; accountability (a physician/pharmacist leader); pharmacy expertise; action (interventions such as prospective audit and feedback, prior authorization); tracking (antibiotic use and resistance); reporting; education.
- Antibiotic time-out: reassess indication, dose, route, duration, and need for de-escalation at 48–72 hours.
- De-escalation: narrow therapy based on culture and susceptibility; stop unnecessary antibiotics; switch IV to oral when feasible.
- Metrics: days of therapy (DOT) and defined daily dose (DDD) per 1,000 patient-days; DOT is preferred for stewardship because it is less affected by dose changes. Antibiotic use is not the same as appropriateness.
- Antibiogram: cumulative susceptibility by organism; use to guide empiric therapy; stratified by unit and specimen type when possible.
- MDRO control: hand hygiene, contact precautions, dedicated equipment, environmental cleaning, screening, and antimicrobial stewardship. CRE, MRSA, VRE, ESBL, and C. difficile require specific policies.
- C. difficile is not an MDRO but is closely tied to antibiotic stewardship; asymptomatic colonization is common, so test only symptomatic patients.
Worked example
A patient with sepsis is started on vancomycin and piperacillin-tazobactam. At 48 hours, cultures grow methicillin-susceptible Staphylococcus aureus and the patient is stable. The stewardship response is to de-escalate to cefazolin or nafcillin, stop vancomycin, and plan a 5–7 day course for uncomplicated bacteremia according to source control. This reduces resistance pressure and toxicity. The DOT metric will capture the change, but the key outcome is appropriate therapy.
Traps
Do not use a positive culture without clinical signs to treat colonization. Do not continue broad-spectrum agents because the patient is improving. Do not compare DOT across facilities without adjusting for patient mix. Do not assume the antibiogram applies to a different unit or specimen.