Summary
A new general susceptibility subsection in the microbiology checklist consolidates requirements for antibacterials, antifungals, and antimycobacterials, aiming for clarity and a broader focus beyond bacteriology. This subsection includes requirements for standardized inoculum, selection of antimicrobial agents, cumulative susceptibility data, and investigation of inconsistent results. Additionally, the checklist revises the bacteriology susceptibility test QC frequency requirement, allowing for extended external QC frequency with proper risk assessment and approval.
Microbiology checklist
Valerie Neff Newitt
April 2026—A new general susceptibility subsection is in the microbiology checklist in the new accreditation checklist edition released late last year.
In the same checklist, in the bacteriology susceptibility testing section, the requirement on susceptibility test QC frequency has been revised to expand quality control frequency options.
The new general susceptibility subsection, located in the general microbiology section of the checklist, consists of requirements previously found in the bacteriology or mycology sections, or both, and that have now been merged. The requirements apply to antibacterials, antifungals, and antimycobacterials. Requirements that are specific to a subdiscipline—bacteriology, mycology, mycobacteriology—remain in their respective sections.
“The goal is to provide clarity and predictability,” says CAP Checklists Committee member Carol A. Rauch, MD, PhD, adjunct associate professor of pathology, microbiology, and immunology at Vanderbilt University School of Medicine. To achieve both, related requirements have been grouped by theme. At the same time, she says, “there has also been an effort to broaden the focus of laboratories beyond bacteriology.”
Among the requirements grouped in the new subsection (and renumbered and revised) is MIC.12010 Standardized Inoculum, which says acceptable inoculum for susceptibility testing must be defined. Acceptable cell density or cell load used for inoculation must be defined, and guidelines for inoculum preparation for antimicrobial susceptibility testing must be followed.
“You have to pay attention to how you do this, and there are standards development organizations that tell you how to do it,” Dr. Rauch explains. “If you don’t pay careful attention to your technique, you can skew your results.”
Also in the subsection and renumbered is MIC.12020 Selection of Antimicrobial Agents to Report, which requires that the laboratory ensure that only antimicrobial agents appropriate for the organism and body site are reported routinely. It applies to antibacterial, antifungal, and antimycobacterial agents tested in the laboratory.
“The point is to broaden the thinking beyond just bacteria,” Dr. Rauch says, noting it’s important to pay attention to the scope of the requirement. Also included is brief guidance on how to select the agents, as well as a recommendation to consult with the antimicrobial stewardship team and other institutional stakeholders to develop a list of antimicrobial agents to be reported for specific organisms isolated from various body sites.
MIC.12040 Cumulative Antimicrobial Susceptibility Data requires microbiology laboratories that provide primary testing for hospitals to maintain and report cumulative antimicrobial susceptibility test data to the medical staff at least yearly. The note says the organisms (bacteria, fungi, and mycobacteria) to include as part of the annual antibiogram should be decided at the institutional level.