An SHV-Derived Extended-Spectrum β-Lactamase in Pseudomonas aeruginosa

A clinical isolate of Pseudomonas aeruginosa RP-1 produced the extended-spectrum β-lactamase (ESBL) SHV-2a. Its gene was expressed from a composite promoter made of the −35 region derived from the left inverted repeat of IS26 and the −10 region from the bla(SHV-2a) promoter itself. The DNA sequences immediately surrounding bla(SHV-2a) were homologous to plasmid pMPA2a from Klebsiella pneumoniae KpZU-3, while further away and 3′ to the bla(SHV-2a) gene, a sequence corresponding to the left end of Tn1721 was detected, thus indicating a likely enterobacterial origin of this ESBL gene.