LIMITATION OF NATIONAL ANTIBIOGRAM

Cumulative antibiogram is a report generated by analyzing antimicrobial susceptibility test results (usually from a single health care facility) from a defined period of time that reflects the percentage of first isolates (per patient) of a given species or organism group that is susceptible to each of the antimicrobial agents routinely tested. An antibiogram is different from the antimicrobial susceptibility profile of an organism reported with an individual patient’s microbiology culture results. The preparation, reporting and utilization of the antibiogram can be customized to meet the needs of each institution.

Antibiograms can be used by clinicians as a general guide to help with empiric antimicrobial therapy decisions while the definitive susceptibility testing results are pending or not available. The antibiogram are also useful when the organism is not yet known. Using the most common pathogens isolated at the facility, clinicians can select a treatment based on known causative pathogens for the suspected infection site. Thus, antibiograms are useful tools for improving antimicrobial prescribing and for developing antimicrobial stewardship policies.

While antibiograms are useful, it is important to consider several limitations when using antibiograms to determine a patient's antimicrobial regimen:

• Antibiograms do not include the time of the sample collection relative to the hospital admission making it challenging to differentiate between community-onset and hospital-onset infections.

• Antibiograms do not differentiate between pathogens and colonizers.

• Antibiogram is not helpful for empiric therapy decisions for patients with recurrent or recent infection and prior antibiotic use. Instead, users should use the patient’s microbiology results and antimicrobial history to determine the best treatment.

• Antibiograms do not provide quantitative MIC data.

• Antibiograms do not include any pharmacokinetic factors such as site of infection, pharmacokinetic/pharmacodynamic parameters, contraindications, efficacy, safety, Clostridioides difficile risk, or other patient factors. 

References:

1. M100. Performance Standards for Antimicrobial Susceptibility Testing. Clinical and Laboratory Standards Institute. 32nd edition. 2022.

2. M39. Analysis and Presentation of Cumulative Antimicrobial Susceptibility Test Data. Clinical and Laboratory Standards Institute. 5th edition. 2022.

3. https://www.sanfordguide.com/ stewardsip/educational-resources/all-about-antibiotic. Resources | Antibiograms - Interpretation & Use (sanfordguide.com)