Carbapenem-Resistant Enterobacterales, Carbapenem Resistant Organisms, Carbapenemase-Producing Enterobacterales, and Carbapenemase-Producing Organisms: Terminology Past its "Sell-By Date" in an Era of New Antibiotics and Regional Carbapenemase Epidemiology.

Carbapenem resistance in Gram-negative bacteria is a public health concern. Consequently, numerous government and agency reports discuss carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant organisms (CROs). Unfortunately, these terms are fuzzy. Do they include (1) Proteeae with inherent imipenem resistance; (2) porin-deficient Enterobacterales resistant to ertapenem but not other carbapenems; (3) Enterobacterales with OXA-48-like enzymes that remain "carbapenem susceptible" at breakpoint; and (4) Pseudomonas aeruginosa that merely lack porin OprD? Counting CPE or CPOs is better but still insufficient, because different carbapenemases have differing treatment implications, particularly for new β-lactam/β-lactamase inhibitor combinations. At the least, it is essential for authors, journals, and regulatory agencies to specify the carbapenemases meant. The future may demand even greater precision, for mutations can alter hydrolytic activity, and the ability to confer resistance, within carbapenemase families.