Table 1.

Detection of presumptive extended spectrum beta-lactamase- (ESBL-) and carbapenemase- (CPM-) producing Enterobacterales from 20 stool specimens before and after storage at − 80 °C

Time point	Pink colonies*		Blue colonies†
	ESBL plate	KPC plate	ESBL plate	KPC plate
Fresh	19 (95)	1 (5)	10 (50)	1 (5)
Frozen #1	19 (95)	1 (5)	12 (60)	0 (0)
Frozen #2	19 (95)	1 (5)	12 (60)	0 (0)
p value‡	1.0	1.0	0.5	0.2

*Indicative of Escherichia coli

^†Indicative of Klebsiella sp., Enterobacter sp., or Citrobacter sp. (KEC group)

^‡Chi-squared test for trend (column values)