Molecular characterization of chromosomal class C beta-lactamase and its regulatory gene in Ochrobactrum anthropi.
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, ampR and ampC, 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 AmpC beta-lactamase (pI, 8.9) was only 41 to 52% identical to the sequence of other chromosomally encoded and plasmid-encoded class C beta-lactamases. The kinetic properties of this beta-lactamase were typical for this class of beta-lactamases. Upstream from the ampC gene, the ampR gene encodes a protein with a sequence that is 46 to 62% identical to those of other AmpR 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 ampC genes of the six reference strains were 96 to 99% identical to the sequence of the clinical strain. The beta-lactamase characterized from strain SLO74 was named OCH-1 (gene, bla(OCH-I)).
Nadjar
D
D
Laboratoire de Bactériologie, Hôpital Tenon, UFR Saint-Antoine, Paris, France.
Labia
R
R
Cerceau
C
C
Bizet
C
C
Philippon
A
A
Arlet
G
G
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002875:Chromosomes; D002876:Chromosomes, Bacterial / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D018432:Drug Resistance, Multiple / Q000235:genetics; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D020621:Ochrobactrum anthropi / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D017931:DNA Primers; D047090:beta-Lactams; D001618:beta-Lactamases