Table 2.

Contribution of different resistance mechanisms to the minimum inhibitory concentrations (MICs) of various carbapenems amongst 47 extensively drug-resistance Pseudomonas aeruginosa isolates.

Resistance mechanisma	Number of isolates	MIC (μg/mL)
		Imipenem			Meropenem			Doripenemb
		Range	MIC50	MIC90	Range	MIC50	MIC90	Range	MIC50	MIC90
OprD	7	32–32	32	32	8–64	32	64	4 to >32	16	>32
VIM	12	32 to >256	32	128	8–256	32	128	4 to >32	>32	>32
OprD + VIM
Overall	28	32–256	256	256	8–256	128	128	12 to >32	>32	>32
Altered MexA	5	32–256	32	256	8–256	32	128	32 to >32	>32	>32
Normal MexA	23	32–256	256	256	32–256	128	128	12 to >32	>32	>32

MIC_50/90, MICs that inhibited the growth of 50% and 90% of the organisms, respectively.

^aIsolates with either reduced OprD expression only or the presence of bla_VIM only, or both, were designated as ‘OprD’, ‘VIM’ and ‘OprD + VIM’, respectively.

^bMICs of doripenem were determined using Etest only.