TABLE 1.

Evolution of CLSI carbapenemase testing recommendations

Time period or year	CLSI recommendations in M100
Pre-2000	No specific recommendations regarding carbapenem resistance testing
2000s	Recognition of the threat of KPC-expressing K. pneumoniae
	Recognition that carbapenem breakpoints were unlikely to predict clinical outcomes for isolates with elevated carbapenem MICs
2009	Introduction of modified Hodge test (MHT) for isolates of Enterobacteriaceae with elevated carbapenem MICs
	If MHT is positive, laboratories instructed to edit all carbapenem results to “R”
2010	Enterobacteriaceae carbapenem breakpoints revised
	Change of recommendation for MHT to “optional” for infection control/epidemiology
2012	Pseudomonas aeruginosa carbapenem breakpoints revised
	Carba NP test introduced for Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter spp.
2014	Acinetobacter spp. carbapenem breakpoints revised
2017	mCIM for Enterobacteriaceae introduced
2018	MHT eliminated
	eCIM introduced for Enterobacteriaceae
	Carba NP for Acinetobacter spp. removed
	mCIM for P. aeruginosa introduced