DNA sequence analysis of regions surrounding blaCMY-2 from multiple Salmonella plasmid backbones.
The emergence in the United States of resistance to expanded-spectrum cephalosporin (e.g., ceftriaxone) within the salmonellae has been associated primarily with three large (>100-kb) plasmids (designated types A, B, and C) and one 10.1-kb plasmid (type D) that carry the blaCMY-2 gene. In the present study, the distribution of these four known blaCMY-2-carrying plasmids among 35 ceftriaxone-resistant Salmonella isolates obtained from 1998 to 2001 was examined. Twenty-three of these isolates were Salmonella enterica serotype Newport, 10 were Salmonella enterica serotype Typhimurium, 1 was Salmonella enterica serotype Agona, and 1 was Salmonella enterica serotype Reading. All 23 serotype Newport isolates carried a type C plasmid, and 5, 4, and 1 serovar Typhimurium isolate carried type B, A, and C plasmids, respectively. Both the serotype Agona and serotype Reading isolates carried type A plasmids. None of the isolates carried a type D plasmid. Hybridization data suggested that plasmid types A and C were highly related replicons. DNA sequencing revealed that the region surrounding blaCMY-2 was highly conserved in all three plasmid types analyzed (types B, C, and D) and was related to a region surrounding blaCMY-5 from the Klebsiella oxytoca plasmid pTKH11. These findings are consistent with a model in which blaCMY-2 has been disseminated primarily through plasmid transfer, and not by mobilization of the gene itself, to multiple Salmonella chromosomal backbones.
Department of Biology, University of Nebraska--Lincoln, Nebraska, USA.
W P
WP
Giles
A K
AK
Benson
M E
ME
Olson
R W
RW
Hutkins
J M
JM
Whichard
P L
PL
Winokur
P D
PD
Fey
D015373:Bacterial Typing Techniques; D001483:Base Sequence; D015139:Blotting, Southern; D017931:DNA Primers; D004269:DNA, Bacterial / Q000032:analysis* / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D022761:Gene Transfer, Horizontal; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D012093:Replicon / Q000235:genetics; D012475:Salmonella / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
D017931:DNA Primers; D004269:DNA, Bacterial; C103022:beta-lactamase CMY-2; D001618:beta-Lactamases