cThis study reported and analyzed the complete sequences of two oqxAB-bearing IncHI2 plasmids harbored by a clinical Salmonella enterica serovar Typhimurium strain and an S. Indiana strain of animal origin, respectively. In particular, pA3T recovered from S. Indiana comprised the resistance determinants oqxAB, aac(6=)Ib-cr, fosA3, and bla CTX-M-14 . Further genetic screening of 63 oqxAB-positive Salmonella isolates revealed that the majority carried IncHI2 plasmids, confirming that such plasmids play a pivotal role in dissemination of oqxAB in Salmonella spp.

This study reports the complete sequence of pE80, a conjugative IncFII plasmid recovered from an Escherichia coli strain isolated from chicken meat. This plasmid harbors multiple resistance determinants including oqxAB, fosA3, blaCTX-M-55, and blaTEM-1, and is a close variant of the recently reported p42-2 element, which was recovered from E. coli of veterinary source. Recovery of pE80 constitutes evidence that evolution or genetic re-arrangement of IncFII type plasmids residing in animal-borne organisms is an active event, which involves acquisition and integration of foreign resistance elements into the plasmid backbone. Dissemination of these plasmids may further compromise the effectiveness of current antimicrobial strategies.