Antimicrobial resistance (AMR) is not a distant threat—it is an evolving crisis that already affects patients in emergency departments (EDs) worldwide. The World Health Organization has identified AMR as one of the top global public health threats. Between 2025 and 2050, AMR is projected to cause 39.1 million deaths directly and contribute to an additional 169 million deaths globally. In Canada, 2018 data revealed that 26% of infections were resistant to first-line antibiotics. That same year, AMR was linked to over 14,000 deaths and an estimated $2 billion reduction in GDP (see full report). These numbers are expected to rise sharply without significant intervention. For emergency physicians, AMR is more than a public health issue—it is a growing barrier to delivering effective, timely care.
This blog post will focus on four key resistant organisms—MRSA, VRE, ESBL, and CPE—with an emphasis on MRSA, the most commonly encountered in emergency medicine.
*Effectiveness of clindamycin is dependent on previous cultures for an individual patient and antibiograms in the community. In Ottawa, MRSA is only 35% susceptible to Clindamycin from the 2022 UOHI Antibiogram and 77.8% susceptible in the Antibiogram from 2021 in Ontario.
**Dalbavancin is not currently readily available in Canada but is an emerging antibiotic that may become clinically relevant for MRSA coverage in the ED, particularly in unhoused populations.
***For single dose treatment of UTI with Fosfomycin, the patient must be highly reliable, without any comorbidities and fit for discharge. Meropenem is first line for ESBL in almost all cases.
Note: Linezolid and daptomycin are currently very expensive and often require special access
Emergency physicians are on the front lines in the fight against antimicrobial resistance (AMR), often prescribing antibiotics under time pressure and with limited diagnostic tools. While Canadian EDs generally demonstrate better stewardship than many international counterparts, inappropriate antibiotic use remains common and continues to fuel resistance.
Key Points:
- Antimicrobial resistance is rising both in Canada and globally, with significant health care and economic consequences.
- Hand hygiene and contact precautions are simple yet crucial interventions to curb the spread of resistant organisms.
- Many resistant organisms—such as MRSA—are primarily transmitted within hospitals, often via transient colonization of health care workers’ hands or contaminated surfaces.
- A 90% hand hygiene compliance rate is widely cited as a target, but most institutions currently fall short of this benchmark.
MRSA (Methicillin-Resistant Staphylococcus aureus)
- Methicillin-resistant Staphylococcus aureus (MRSA) is a gram-positive coccus that is resistant to a class of antibiotics known as beta-lactams. These include penicillins, cephalosporins, and carbapenems, all characterized by their distinctive beta-lactam ring.
- MRSA is a socioeconomic disease, disproportionately affecting marginalized populations including Indigenous communities, unhoused individuals, people living in crowded environments, and those who use intravenous drugs.
- MRSA commonly presents as skin and soft tissue infections (SSTIs), such as abscesses or cellulitis. Globally, MRSA is associated with the greatest increase in antimicrobial resistance; the number of deaths attributable to MRSA doubled between 1990 and 2021. Rates of MRSA continue to rise in hospitals and emergency departments across Canada and worldwide.
- Routine swabbing of purulent skin and soft tissue infections (SSTIs), especially abscesses, is recommended for MRSA detection.
- Follow your institution’s anti-infective guidelines for antibiotic selection. Some important notes:
- Clindamycin may be less effective than other agents; if considering its use, review prior susceptibility data.
- Daptomycin is non-inferior to vancomycin and has a safer side effect profile. It may be considered—particularly in recurrent MRSA infections—in consultation with Infectious Diseases.
- Dalbavancin is an emerging agent with potential to change emergency medicine practice.
Management
- Canadian Association of Emergency Physicians (CAEP) Guidelines (2020):
- Incision and drainage (I&D) alone is effective for approximately 70% of patients, even in MRSA cases.
- Antibiotics may be beneficial in addition to I&D, particularly in patients with:
- Recurrent or multiple abscesses
- Significant risk factors for MRSA
- Limited follow-up
- If community MRSA prevalence exceeds 10%, strongly consider choosing an antibiotic with MRSA coverage.
- Swab all abscesses and purulent SSTIs to estimate local MRSA prevalence, assess susceptibility, and inform patient follow-up and education.
• Canadian ED Best Practice Checklist – Oral and IV Options for MRSA Coverage:
*Note: Clindamycin susceptibility is decreasing. Ottawa’s 2022 antibiogram reports 35% susceptibility, and Ontario-wide 2021 data shows 77.8% susceptibility. Consider local data and patient history when prescribing.
Transmission Prevention:
- MRSA is frequently spread via transient colonization of health care workers’ hands.
- Emphasize hand hygiene and contact precautions.
- Instruct patients to:
- Cover wounds
- Perform regular hand hygiene
- Avoid sharing contaminated items like bedding or razors
High Risk Populations
- MRSA is increasingly recognized as a socioeconomic disease:
- In Canada, Indigenous populations are disproportionately affected, with rates up to 10 times higher than in non-Indigenous populations.
- Lower income is a risk factor: a $100,000 increase in income is associated with a 73% reduction in MRSA risk.
Treatment Considerations:
- Daptomycin is an alternative to vancomycin for resistant MRSA infections:
- It is non-inferior, associated with fewer side effects, and linked to lower mortality.
- Access in the ED is limited—consult Infectious Diseases if daptomycin is being considered.
- According to Infectious Diseases expert Dr. Lydia Xing:
- For well-appearing patients with risk factors, consider trialing a beta-lactam (e.g., cephalexin), as MSSA remains more common and more susceptible.
- For unwell patients, empirically cover for MRSA.
Emerging Therapies
Dalbavancin is a promising new agent with activity against both MRSA and MSSA, as well as other gram-positive organisms. Benefits include:
- Single-dose treatment, ideal for patients who are unhoused or have poor follow-up
- Fewer side effects
- Potentially lower mortality
- Early evidence of efficacy in treating more serious infections such as endocarditis and pneumonia
Other Resistant Organisms
- VRE (Vancomycin-Resistant Enterococcus) and CPE (Carbapenemase-Producing Enterobacteriaceae):
- Consult Infectious Diseases for antibiotic recommendations. In Canada, all confirmed CPE cases must be reported to public health authorities.
- ESBL (Extended-Spectrum Beta-Lactamase–producing organisms): Meropenem is the first-line treatment.
- More details on MRSA, VRE, ESBL, and CPE are provided below. For a refresher on antibiotic classes, scroll to the bottom of the blog post.
https://www.compoundchem.com/2014/09/08/antibiotics/
VRE – Vancomycin Resistant Enterococcus
- A group of gram-positive enterococci resistant to vancomycin.
- Rates of VRE have increased significantly in Canada—up 72.2% between 2016 and 2022.
- 93% of infections are health care–associated, commonly seen in patients with recent hospitalizations and in older adults.
- Urinary tract infections (UTIs) are the most frequently reported VRE-related infections.
Treatment options:
- Linezolid (oral or IV)
- Daptomycin (IV only)
•Both medications are expensive, often require special access, and should be prescribed in consultation with Infectious Diseases.
ESBL – Extended-Spectrum Beta-Lactamase–Producing Organisms
- A diverse group of gram-negative bacteria that produce enzymes capable of cleaving the beta-lactam ring, rendering many beta-lactam antibiotics ineffective.
- These organisms may retain susceptibility to higher-generation cephalosporins and carbapenems.
- First-line treatment:
- Meropenem is typically used; however, prior culture results should guide management when available
CPE – Carbapenemase-Producing Enterobacteriaceae
- Gram-negative bacteria that produce carbapenemase, an enzyme that deactivates carbapenems and other beta-lactam antibiotics.
- CPE has been reportable to public health in Canada since 2018, with most cases linked to travelers returning from the Indian subcontinent.
- Cases and rates of CPE have been steadily rising in Ontario since reporting began.
- CPE is extremely difficult to treat, and management should always involve Infectious Diseases consultation.
https://www.compoundchem.com/2014/09/08/antibiotics/
