New carbenicillin-hydrolyzing beta-lactamase (CARB-7) from Vibrio cholerae non-O1, non-O139 strains encoded by the VCR region of the V. cholerae genome.
In a previous study, an analysis of 77 ampicillin-nonsusceptible (resistant plus intermediate categories) strains of Vibrio cholerae non-O1, non-O139, isolated from aquatic environment and diarrheal stool, showed that all of them produced a beta-lactamase with a pI of 5.4. Hybridization or amplification by PCR with a probe for bla(TEM) or primers for bla(CARB) gene families was negative. In this work, an environmental ampicillin-resistant strain from this sample, ME11762, isolated from a waterway in the west region of Argentina, was studied. The nucleotide sequence of the structural gene of the beta-lactamase was determined by bidirectional sequencing of a Sau3AI fragment belonging to this isolate. The gene encodes a new 288-amino-acid protein, designated CARB-7, that shares 88.5% homology with the CARB-6 enzyme; an overall 83.2% homology with PSE-4, PSE-1, CARB-3, and the Proteus mirabilis N29 enzymes; and 79% homology with CARB-4 enzyme. The gene for this beta-lactamase could not be transferred to Escherichia coli by conjugation. The nucleotide sequence of the flanking regions of the bla(CARB-7) gene showed the occurrence of three 123-bp V. cholerae repeated sequences, all of which were found outside the predicted open reading frame. The upstream fragment of the bla(CARB-7) gene shared 93% identity with a locus situated inside V. cholerae's chromosome 2. These results strongly suggest the chromosomal location of the bla(CARB-7) gene, making this the first communication of a beta-lactamase gene located on the VCR island of the V. cholerae genome.
Melano
Roberto
R
Servicio Antimicrobianos, Departamento de Bacteriología, Instituto Nacional de Enfermedades Infecciosas-ANLIS Dr. Carlos G. Malbrán, Buenos Aires, Argentina.
Petroni
Alejandro
A
Garutti
Alicia
A
Saka
Héctor Alex
HA
Mange
Laura
L
Pasterán
Fernando
F
Rapoport
Melina
M
Rossi
Alicia
A
Galas
Marcelo
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D002228:Carbenicillin / Q000378:metabolism*; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D016680:Genome, Bacterial; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D014734:Vibrio cholerae / Q000187:drug effects / Q000235:genetics*; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics*
D001618:beta-Lactamases; D002228:Carbenicillin