Laboratory detection of carbapenemases among Gram-negative organisms

SUMMARYThe carbapenems remain some of the most effective options available for treating patients with serious infections due to Gram-negative bacteria. Carbapenemases are enzymes that hydrolyze carbapenems and are the primary method driving carbapenem resistance globally. Detection of carbapenemases is required for patient management, the rapid implementation of infection prevention and control (IP&C) protocols, and for epidemiologic purposes. Therefore, clinical and public health microbiology laboratories must be able to detect and report carbapenemases among predominant Gram-negative organisms from both cultured isolates and direct from clinical specimens for treatment and surveillance purposes. There is not a "one size fits all" laboratory approach for the detection of bacteria with carbapenemases, and institutions need to determine what fits best with the goals of their antimicrobial stewardship and IP&C programs. Luckily, there are several options and approaches available for clinical laboratories to choose methods that best suits their individual needs. A laboratory approach to detect carbapenemases among bacterial isolates consists of two steps, namely a screening process (e.g., not susceptible to ertapenem, meropenem, and/or imipenem), followed by a confirmation test (i.e., phenotypic, genotypic or proteomic methods) for the presence of a carbapenemase. Direct from specimen testing for the most common carbapenemases generally involves detection via rapid, molecular approaches. The aim of this article is to provide brief overviews on Gram-negative bacteria carbapenem-resistant definitions, types of carbapenemases, global epidemiology, and then describe in detail the laboratory methods for the detection of carbapenemases among Gram-negative bacteria. We will specifically focus on the Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex.