Molecular and Biochemical Characterization of a Novel Class A β-Lactamase (HER-1) from Escherichia hermannii

Abstract

ABSTRACT Escherichia hermannii showed a low level of resistance to amoxicillin and ticarcillin, reversed by clavulanate, and a moderate susceptibility to piperacillin but was susceptible to all cephalosporins. A bla gene was cloned and encoded a typical class A β-lactamase (HER-1, pI 7.5), which shares 45, 44, 41, and 40% amino acid identity with other β-lactamases, AER-1 from Aeromonas hydrophila , MAL-1/Cko-1 from Citrobacter koseri , and TEM-1 and LEN-1, respectively. No ampR gene was detected. Only penicillins were efficiently hydrolyzed, and no hydrolysis was observed for cefuroxime and broad-spectrum cephalosporins. Sequencing of the bla gene in 12 other strains showed 98 to 100% identity with bla HER-1 .