TABLE 3.

Stabilities of THF carbapenems to hydrolysis by serine β-lactamases

β-Lactam	Relative hydrolysis rate (%) by the following enzyme (functional group)a:
	P99 (1)	PC1 (2a)	TEM-2 (2b)	TEM-26 (2be)
Cephaloridineb	100	NDc	ND	ND
Benzylpenicillin	ND	100	100	100
Imipenem	0.01	≤0.01	0.03	0.28
CL 188,624	0.12	≤0.01	0.02	0.27
CL 190,294	0.01	≤0.01	0.01	0.29
CL 191,121	0.29	≤0.01	0.16	0.60

^aRelative hydrolysis rate was calculated on the basis of 100% hydrolysis of the reference β-lactam. Functional groups are those of Bush et al. (6). 

^bCephaloridine was selected as the reference compound for the group 1 β-lactamase P99; benzylpenicillin was selected as reference compound for the group 2 β-lactamases. 

^cND, not determined.