Expression of Aeromonas caviae bla genes in Escherichia coli

An isolate of Aeromonas caviae 035 carried a 55.5 kb self-transferable plasmid. Transfer of the plasmid to Escherichia coli K12 resulted in the expression of a TEM-like beta-lactamase that was not expressed in parental A. caviae. The bla gene sequence was detectable by DNA hybridization and PCR amplification of the plasmid when extracted from parental A. caviae or from E. coli K12 transconjugants. Sequence analysis of the bla genes revealed in each case an 858 bp open reading frame, differing from the TEM-1 sequence by five nucleotide substitutions. Only one of these resulted in amino acid substitution (at position 162 serine-->arginine). The sequence most closely resembles that of TEM-12.