
<ArticleTitle>Molecular characterization of chromosomal <prot>class C beta-lactamase</prot> and its regulatory gene in Ochrobactrum anthropi.</ArticleTitle>
<AbstractText>Ochrobactrum anthropi, formerly known as CDC group Vd, is an oxidase-producing, gram-negative, obligately aerobic, non-lactose-fermenting bacillus of low virulence that occasionally causes human infections. It is highly resistant to all beta-lactams except imipenem. A clinical isolate, SLO74, and six reference strains were tested. MICs of penicillins, aztreonam, and most cephalosporins tested, including cefotaxime and ceftazidime, were 128 microg/ml and of cefepime were 64 to 128 microg/ml. Clavulanic acid was ineffective and tazobactam had a weak effect in association with piperacillin. Two genes, <prot>ampR</prot> and <prot>ampC</prot>, were cloned by inserting restriction fragments of genomic DNA from the clinical strain O. anthropi SLO74 into pBK-CMV to give the recombinant plasmid pBK-OA1. The pattern of resistance to beta-lactams of this clone was similar to that of the parental strain, except for its resistance to cefepime (MIC, 0.5 ,micro/ml). The deduced amino acid sequence of the <prot>AmpC</prot> <prot>beta-lactamase</prot> (pI, 8.9) was only 41 to 52% identical to the sequence of other chromosomally encoded and plasmid-encoded <prot>class C beta-lactamase</prot>s. The kinetic properties of this beta-lactamase were typical for this class of <prot>beta-lactamase</prot>s. Upstream from the <prot>ampC</prot> gene, the <prot>ampR</prot> gene encodes a protein with a sequence that is 46 to 62% identical to those of other <prot>AmpR</prot> proteins and with an amino-terminal DNA-binding domain typical of transcriptional activators of the Lys-R family. The deduced amino acid sequences of the <prot>ampC</prot> genes of the six reference strains were 96 to 99% identical to the sequence of the clinical strain. The <prot>beta-lactamase</prot> characterized from strain SLO74 was named <prot>OCH-1</prot> (gene, <prot>bla</prot>(<prot>OCH-I</prot>)).</AbstractText>
