Antimicrobial Stewardship (AMS)

Definition

• Harrison's Principles of Internal Medicine 22E, p. 1222
• Sherris & Ryan's Medical Microbiology, 8th Ed., p. 957

Why AMS Matters

1. Rising antimicrobial resistance - multidrug-resistant (MDR) organisms are spreading globally; a "post-antibiotic era" is a real risk in some settings
2. Inappropriate use - a large proportion of prescriptions (especially in outpatient settings) are unnecessary or suboptimal
3. Adverse effects - antibiotic use causes Clostridioides difficile infection, organ toxicity, allergic reactions, and microbiome disruption
4. Cost - pharmaceuticals are the largest and fastest-growing segment of healthcare costs; formulary management is critical
5. Collateral damage - broad-spectrum agents harm beneficial commensal microbiota alongside pathogens

"Everyone shares responsibility for the current crisis of resistance - the veterinarians who use it in farm animals, the politicians, the insurance companies, the drug manufacturers, the patients, and the providers who prescribe." - Sherris & Ryan's, p. 958

The Four Core Goals of an AMS Program

The CDC's 7 Core Elements of Hospital AMS Programs

1. Hospital Leadership Commitment - Dedicate human, financial, and IT resources; formal board-level support; designate an executive champion
2. Accountability - Appoint a physician leader (and ideally a co-leader pharmacist) responsible for program management and outcomes
3. Pharmacy Expertise - A clinical pharmacist (ideally ID-trained) co-leads implementation efforts
4. Action - Implement evidence-based interventions (see below)
5. Tracking - Monitor antibiotic use data (days of therapy/1,000 patient-days), C. diff rates, resistance trends, length of stay, adverse drug events; use NHSN's Antimicrobial Use and Resistance (AUR) module
6. Reporting - Provide regular updates to prescribers, pharmacists, nurses, and hospital leadership
7. Education - Annual education for all healthcare workers; patient/family education

The AMS Team (Multidisciplinary)

• Infectious disease (ID) physicians
• Clinical pharmacists with ID specialty training
• Clinical microbiologists
• Hospital epidemiologists
• Infection prevention and control practitioners
• Information systems/IT specialists
• Nurses

Core AMS Interventions (Actions)

1. Prospective Audit and Feedback (PAF)

2. Formulary Restriction

3. Preauthorization

4. IV-to-Oral (IV-to-PO) Conversion

5. Dose Optimization

6. Implementation of Facility-Specific Treatment Guidelines

7. De-escalation

Principles for Individual Prescribers (The "Steward's Checklist")

1. Establish a firm diagnosis - Is this truly a bacterial infection? Obtain cultures before starting therapy whenever possible (but never delay treatment in sepsis/meningitis)
2. Guide empiric therapy - Use local antibiogram data, patient-specific factors (allergy, prior exposure, renal function, site of infection), and severity of illness
3. De-escalate when possible - Trust culture data; narrow spectrum as soon as possible
4. Shorter may be better - Use the briefest effective duration; subtherapeutic dosing is bad practice, but appropriately short courses reduce resistance pressure
5. Maintain infection control - Hand hygiene, contact precautions, and environmental cleaning prevent transmission of resistant organisms
6. Say NO to antibiotics for viral infections - Rhinosinusitis is viral ~95% of the time; antibiotics do not help and cause harm
7. Collaborate with ID specialists - Consult for severe illness, treatment failure, unexpected resistance profiles, or complex multi-drug regimens

Outpatient vs. Inpatient AMS

Pediatric AMS - "Choosing Wisely" (AAP/PIDS)

• Do NOT start empiric antibiotics for suspected invasive bacterial infection without first obtaining appropriate cultures
• Do NOT use broad-spectrum antimicrobials for perioperative prophylaxis or continue prophylaxis after wound closure
• Do NOT treat uncomplicated community-acquired pneumonia in healthy, immunized, hospitalized children with anything broader than ampicillin
• Do NOT use vancomycin or carbapenems empirically in neonatal ICU patients unless specific resistance risk factors are present
• Do NOT place PICCs or use prolonged IV antibiotics in otherwise healthy children who can tolerate oral therapy

Measuring AMS Success

• Days of Therapy (DOT) per 1,000 patient-days (preferred over DDD for inpatient monitoring)
• Standardized Antimicrobial Administration Ratio (SAAR) via NHSN AUR module - benchmarks against similar institutions
• Hospital-onset C. difficile infection rates
• Rates of MDR organisms (MRSA, CRE, VRE)
• Length of stay and adverse drug events
• Antibiotic costs

Key Regulatory & Policy Context

• CDC Core Elements (2019 revision) - foundational framework
• The Joint Commission (TJC) Medication Management Standards - require formal ASPs in accredited hospitals
• CMS Conditions of Participation - tie stewardship to hospital reimbursement
• 2015 U.S. National Action Plan for Combating Antibiotic-Resistant Bacteria (CARB) - federal mandate for AMS programs
• ESCMID 2024 ED Guidelines - first dedicated guidance for emergency department stewardship (PMID: 39029872)

Recent Evidence (2023-2024)

• ESCMID ED AMS Guidelines (2024) - first systematic review-backed guidelines specifically for antimicrobial stewardship in emergency departments
• Role of Clinical Pharmacists in AMS (2023) - systematic review confirming pharmacist-led stewardship interventions significantly reduce inappropriate antibiotic use, costs, and C. diff rates
• Diagnostic stewardship (PMID: 37061101) is increasingly recognized as a continuum of AMS - using the right diagnostic test at the right time to guide antibiotic decisions