Chromosome-Encoded Class D β-Lactamase OXA-23 in Proteus mirabilis

Ten nonrepetitive Proteus mirabilis isolates, which were collected over 4 years (1996 to 1999) at the teaching hospital of Clermont-Ferrand, France, produced class D carbapenemase OXA-23. MICs of imipenem were 0.25 to 0.5 μg/ml for these clinical isolates. Molecular typing revealed that the 10 P. mirabilis isolates originated from the same clonal strain. Hybridization of I-CeuI-generated chromosome fragments with a bla(OXA-23) probe showed that the gene was chromosome encoded in the P. mirabilis strain.