Cloning, nucleotide sequencing, and analysis of the gene encoding an AmpC β-lactamase in Acinetobacter baumannii

A clinical strain of Acinetobacter baumannii (strain Ab RYC 52763/97) that was isolated during an outbreak in our hospital and that was resistant to all beta-lactam antibiotics tested produced three beta-lactamases, a TEM-1-type (pI, 5.4) plasmid-mediated beta-lactamase, a chromosomally mediated OXA-derived (pI, 9.4) beta-lactamase, and a presumptive chromosomal cephalosporinase (pI, 9.4). The nucleotide sequence of the chromosomal cephalosporinase gene shows for the first time the gene encoding an AmpC beta-lactamase in A. baumannii. In addition, we report here the biochemical properties of this A. baumannii AmpC beta-lactamase.