CHARACTERIZATION OF BETA-LACTAMASE GENE BLA(PER-2,) WHICH ENCODES AN EXTENDED-SPECTRUM CLASS-A BETA-LACTAMASE

Plasmidic extended-spectrum beta-lactamases of Ambler class A are most ly inactive against ceftibuten. Salmonella typhimurium JMC isolated in Argentina harbors a bla gene located on a plasmid (pMVP-5) which conf ers transferable resistance to oxyiminocephalosporins, aztreonam, and ceftibuten. The beta-lactamase PER-2 (formerly ceftibutenase-1; CTI-1) is highly susceptible to inhibition by clavulanate and is located at a pI of 5.4 after isoelectric focusing, The bla(PER-2) gene was cloned and sequenced. The nucleotide sequence of a 2.2-kb insert in vector p Bluescript includes an open reading frame of 927 bp. Comparison of the deduced amino acid sequence of PER-2 with those of other beta-lactama ses indicates that PER-2 is not closely related to TEM or SHV enzymes (25 to 26% homology), PER-2 is most closely related to PER-1 (86.4% ho mology), an Ambler class A enzyme first detected in Pseudomonas aerugi nosa, An enzyme with an amino acid sequence identical to that of PER-1 , meanwhile, was found in various members of the family Enterobacteria ceae isolated from patients in Turkey. Our data indicate that PER-2 an d PER-1 represent a new group of Ambler class A extended-spectrum beta -lactamases. PER-2 so far has been detected only in pathogens (S. typh imurium, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis) i solated from patients in South America, while the incidence of PER-1-p roducing strains so far has been restricted to Turkey, where it occurs both in members of the family Enterobacteriaceae and in P. aeruginosa .