PME-1, an extended-spectrum β-lactamase identified in Pseudomonas aeruginosa

Abstract

A novel extended-spectrum β-lactamase (ESBL) was identified in a Pseudomonas aeruginosa clinical isolate obtained from a patient admitted to a hospital in Pennsylvania in 2008. The patient had a prolonged hospitalization in a hospital in Dubai, United Arab Emirates, before being transferred to the United States. The novel ESBL, designated PME-1 (Pseudomonas aeruginosa ESBL 1), is a molecular class A, Bush-Jacoby-Medeiros group 2be enzyme and shared 50, 43, and 41% amino acid identity with the L2 β-lactamase of Stenotrophomonas maltophilia, CTX-M-9, and KPC-2, respectively. PME-1 conferred clinically relevant resistance to ceftazidime, cefotaxime, cefepime, and aztreonam in P. aeruginosa PAO1 but not to carbapenems. Purified PME-1 showed good hydrolytic activity against ceftazidime, cefotaxime, and aztreonam, while activity against carbapenems and cefepime could not be measured. PME-1 was inhibited well by β-lactamase inhibitors, including clavulanic acid, sulbactam, and tazobactam. The bla(PME-1) gene was carried by an approximately 9-kb plasmid and flanked by tandem ISCR24 elements.

Fig. 1.

Alignment of the deduced amino acid sequence of PME-1, along with those of L2 β-lactamase (GenBank accession no. EU032534), CTX-M-9 (GenBank accession no. AJ416345), and KPC-2 (GenBank accession no. DQ523564). The conserved sequences that are typical of class A serine β-lactamases are boxed.

Fig. 2.

Schematic presentation of the genetic environment of bla_PME-1.