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 β-lactam antibiotics tested produced three β-lactamases: a TEM-1-type (pI, 5.4) plasmid-mediated β-lactamase, a chromosomally mediated OXA-derived (pI, 9.0) β-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 β-lactamase in A. baumannii. In addition, we report here the biochemical properties of this A. baumannii AmpC β-lactamase.