Analysis by using DNA probes of the OXA-1 beta-lactamase gene and its transposon.

From recombinant clone pTY27, encoding an OXA-1 beta-lactamase gene, we performed subcloning experiments to more precisely delimit the gene. We describe the use as probes of six different restriction fragments known from subcloning experiments to be within the structural gene or part of the transposable element, Tn2603, flanking the OXA-1 determinant. We showed that the OXA-1 structural gene is slightly related to the OXA-2 determinant and also that sequences within Tn2603 are common to all the OXA- and PSE-producing strains tested. For epidemiological purposes, we began nucleotide sequencing of the OXA-1 determinant, and from preliminary sequence data we synthesized an oligonucleotide 15 bases in length, corresponding to a sequence within the OXA-1 gene. This oligonucleotide was found to be specific for the OXA-1 determinant, because it hybridized only to bacteria producing that beta-lactamase.