Table 2.

Prevalence of acquired carbapenemase-encoding genes and ampC or efflux pump mexB overexpression in carbapenem-non-susceptible isolates.

Resistance genes		No. (%) of isolates
	Overexpressiona	Borderline	No overexpression
ampC	96 (68.09)	12 (8.51)	33 (23.40)
mexBb	17 (12.78)	20 (15.04)	96 (72.18)
IMP-9	11 (7.80)
VIM-2	9 (6.38)

^aThe mRNA levels of the indicated genes in PAO1 were used as controls. Evaluation criteria are as follows: for ampC overexpression indicates expression at least 10-fold higher than in PAO1, negative indicates expression is lower than 5-fold, and borderline indicates expression is between 5- and 10-fold higher. For mexB, overexpression indicates expression at least 3-fold higher, negative indicates expression is less than 2-fold higher, and borderline indicates expression is between 2- and 3-fold higher. ^bTranscription of mexB was determined in 133 meropenem-non-susceptible isolates.