Integration of a Transposon Tn 1 -Encoded Inhibitor-Resistant β-Lactamase Gene, bla TEM-67 from Proteus mirabilis , into the Escherichia coli Chromosome

Abstract

Proteus mirabilis NEL-1 was isolated from a urine sample of a patient hospitalized in a long-term care facility. Strain NEL-1 produced a β-lactamase with a pI of 5.2 conferring resistance to amoxicillin and amoxicillin-clavulanic acid. Sequencing of a PCR amplicon by using TEM-specific primers revealed a novel bla _TEM gene, bla _TEM-67 . TEM-67 was an IRT-1-like TEM derivative related to TEM-65 (Lys39, Cys244) with an additional Leu21Ile amino acid substitution in the leader peptide. The biochemical properties of TEM-67 were equivalent to those described for TEM-65. Analysis of sequences surrounding bla _TEM-67 revealed that it was located on a transposon, Tn 1 , which itself was located on a 48-kb non-self-transferable plasmid, pANG-1. Electroporation of plasmid pANG-1 into Escherichia coli DH10B resulted in the integration of bla _TEM-67 into the chromosome, whereas it remained episomal in the P. mirabilis CIP103181 reference strain. Further characterization of pANG-1 revealed the presence of two identical sequences on both sides of Tn 1 that contained an IS 26 insertion sequence followed by a novel colicin gene, colZ , which had 20% amino acid identity with other colicin genes. The characterization of this novel TEM derivative provides further evidence for the large diversity of plasmid-encoded β-lactamases produced in P. mirabilis and for their spread to other enterobacterial species through transposable-element-mediated events.