Characterization of BKC-1 Class A Carbapenemase from Klebsiella pneumoniae Clinical Isolates in Brazil

Abstract

ABSTRACTThreeKlebsiella pneumoniaeclinical isolates demonstrating carbapenem resistance were recovered from different patients hospitalized at two medical centers in São Paulo, Brazil. Resistance to all β-lactams, quinolones, and some aminoglycosides was observed for these isolates that were susceptible to polymyxin B. Carbapenem hydrolysis, which was inhibited by clavulanic acid, was observed for allK. pneumoniaeisolates that belonged to the same pulsed-field gel electrophoresis (PFGE) type and a novel sequence type (ST), ST1781 (clonal complex 442 [CC442]). A 10-kb nonconjugative incompatibility group Q (IncQ) plasmid, denominated p60136, was transferred toEscherichia colistrain TOP10 cells by electroporation. The full sequencing of p60136 showed that it was composed of a mobilization system, ISKpn23, the phosphotransferase aph3A-VI, and a 941-bp open reading frame (ORF) that codified a 313-amino acid protein. This ORF was namedblaBKC-1. BrazilianKlebsiellacarbapenemase-1 (BKC-1) showed a pI of 6.0 and possessed the highest identity (63%) with a β-lactamase ofSinorhizobium meliloti, an environmental bacterium. Hydrolysis studies demonstrated that purified BKC-1 not only hydrolyzed carbapenems but also penicillins, cephalosporins, and monobactams. However, the carbapenems were less efficiently hydrolyzed due to their very lowkcatvalues (0.0016 to 0.031 s−1). In fact, oxacillin was the best substrate for BKC-1 (kcat/Km, 53,522.6 mM−1s−1). Here, we report a new class A carbapenemase, confirming the diversity and rapid evolution of β-lactamases inK. pneumoniaeclinical isolates.