Types of beta-lactamase determined by plasmids in gram-negative bacteria

Abstract

Two species of .beta.-lactamase determined by plasmids in enteric bacteria [Escherichia coli, Proteus mirabilis, Klebsiella sp.] that show some resemblance to TEM enzymes are described. Both are distinct from all other plasmid-mediated .beta.-lactamases and differ from the TEM .beta.-lactamases in ability to hydrolyze some substrates, in isoelectric point, in immunological specificity and in susceptibility to inhibition. One of the enzyme species, mediated by plasmid p453, was briefly described previously. This .beta.-lactamase, designated SHV-1, is unique in its response to inhibition by the SH group reagent p-chloromercuribenzoate because the hydrolysis of cephaloridine, but not that of benzylpenicillin, is affected. This enzyme is found in a variety of plasmid types which were transferred from several bacterial species collected from a wide geographic range. The other enzyme species is novel; only a single plasmid determining this kind of .beta.-lactamase (designated HMS-1) was detected.