Submitted to: Antimicrobial Agents and Chemotherapy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2009
Publication Date: 2/2/2010
Citation: Call, D.R., Singer, R.S., Meng, D., Broschat, S.L., Orfe, L.H., Anderson, J.M., Herndon, D.R., Kappmeyer, L.S., Daniels, J.B., Besser, T.E. 2010. blaCMY-2-positive IncA/C plasmids from escherichia coli and salmonella enterica are a distinct component of a larger lineage of plasmids. Antimicrobial Agents and Chemotherapy. 54(2):590-6. Interpretive Summary: The DNA sequence was determined and gene content analyzed for 3 plasmids carrying multidrug resistance genes originating from Escherichia coli and Salmonella enterica. Plasmids are extrachromosomal genetic elements that play key roles in the maintenance and dissemination of novel genetic traits in bacterial populations. Antibiotic resistance is one of the most important medicine-related traits that can be encoded by plasmids. Plasmids can be recovered from a range of meat products throughout the United States. The implication of this finding is that agricultural reservoirs have the potential to share these multidrug resistance plasmids with zoonotic agents of significant public health concern. The objective of the current study was to closely examine 3 sources of plasmids to better understand how these plasmids are changing over short periods of time. We report complete plasmid sequences for the blaCMY-2 antibiotic resistance gene-containing plasmid from a strain of S. enterica serovar Newport and from two geographically separated Escherichia coli strains recovered from cattle. We found that most changes in blaCMY-2 plasmids involved insertions and deletions of sequences related to antibiotic resistance, and that the plasmids from E. coli and S. enterica are genetically distinct from plasmid recovered from other pathogenic bacteria.
Technical Abstract: Large multidrug resistance plasmids of the A/C incompatibility complex (IncA/C) have been found in a diverse group of Gram-negative commensal and pathogenic bacteria. We present three completed sequences from IncA/C plasmids that originated from Escherichia coli (cattle) and Salmonella enterica serovar Newport (human) and that carry the cephamycinase gene blaCMY-2. These large plasmids (148 to 166 kbp) share extensive sequence identity and synteny. The most divergent plasmid, peH4H, has lost several conjugationrelated genes and has gained a kanamycin resistance region. Two of the plasmids (pAM04528 and peH4H) harbor two copies of blaCMY-2, while the third plasmid (pAR060302) harbors a single copy of the gene. The majority of single-nucleotide polymorphisms comprise nonsynonymous mutations in floR. A comparative analysis of these plasmids with five other published IncA/C plasmids showed that the blaCMY-2 plasmids from E. coli and S. enterica are genetically distinct from those originating from Yersinia pestis and Photobacterium damselae and distal to one originating from Yersinia ruckeri. While the overall similarity of these plasmids supports the likelihood of recent movements among E. coli and S. enterica hosts, their greater divergence from Y. pestis or Y. ruckeri suggests less recent plasmid transfer among these pathogen groups.