Cloning and expression in Enterobacteriaceae of the extended-spectrum β-lactamase gene from a Pseudomonas aeruginosa plasmid

Abstract An extended-spectrum β-lactamase, the gene for which is located on plasmid pMS350 in Pseudomonas aeruginosa strains, hydrolyzes carbapenems and other extended-spectrum β-lactam antibiotics. We cloned the pMS350 β-lactamase gene in an Escherichia coli K-12 strain using the vector plasmid pHSG398, and subcloned it into pMS360, a plasmid with a wide host-range. This resulted in the formation of the recombinant plasmid, pMS363, containing a 4.1-kb DNA insert that includes the extended-spectrum β-lactamase gene. Plasmid pMS363 was introduced into the P. aeruginosa PAO strain or into six species of Enterobacteriaceae, and the specific activities of the β-lactamase and MICs of various β-lactam antibiotics were estimated. The cloned gene was capable of expression in these strains and caused resistance to carbapenem, penem and other β-lactam antibiotics, with the exception of aztreonam.