Plasmid penicillin resistance in Vibrio cholerae: identification of new beta-lactamase SAR-1

Two strains of Vibrio cholerae biotype El Tor, isolated in Tanzania, possessed a single IncC resistance plasmid of 113 kilobases. Both plasmids encoded the production of a novel beta-lactamase, SAR-1, which was 33,700 daltons in size and was able to hydrolyze carbenicillin as well as penicillin G. The SAR-1 beta-lactamase was quite distinct from all other plasmid beta-lactamases by virtue of its unusually low isoelectric point and a combination of its size, substrate profile, and inhibition properties. This enzyme is only the second beta-lactamase identified in V. cholerae species and the first to be reported in V. cholerae strains isolated in Southern Africa.