Analysis and presentation of cumulative antibiograms: a new consensus guideline from the Clinical and Laboratory Standards Institute.

It is crucial to monitor emerging trends in resistance at the local level to support clinical decision making, infection-control interventions, and antimicrobial-resistance containment strategies. Monitoring of antimicrobial resistance trends is commonly performed in health care facilities using an annual summary of susceptibility rates, known as a cumulative antibiogram report. The Clinical and Laboratory Standards Institute M39-A2 consensus document, entitled "Analysis and Presentation of Cumulative Antimicrobial Susceptibility Test Data," provides guidance to clinical laboratories in the preparation of a cumulative antibiogram. The purpose of this review is to describe this document, explain the rationale for some of the recommendations, discuss limitations of its use, and propose new directions for future revisions. The document contains specific recommendations for the collection, storage, analysis, and presentation of data and includes sample templates highlighting the recommendations. Critical issues include the recommended frequency of reporting, the number of isolates to include in a statistic, and a mechanism for eliminating multiple isolates of a given bacterial species obtained from an individual patient.