bla(KPC) RNA expression correlates with two transcriptional start sites but not always with gene copy number in four genera of Gram-negative pathogens.

Klebsiella pneumoniae carbapenemase (KPC)-producing organisms are therapeutically and diagnostically challenging. It is possible that bla(KPC) gene expression plays a role in the variability observed in clinical susceptibility testing. bla(KPC) transformants together with 10 clinical isolates representing four genera were evaluated for bla(KPC) copy number and gene expression and correlated with β-lactam MIC data. The data suggest that mechanisms other than gene copy number and expression of bla(KPC) contribute to variability in susceptibility when testing KPC-producing isolates.