Submitted to: Plasmid Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 21, 2009
Publication Date: January 25, 2010
Citation: Chen, C., Strobaugh Jr, T.P., Frye, J.G. 2010. Characterization of Small ColE1-Like Plasmids Conferring Kanamycin Resistance in Salmonella enterica subsp. enterica serovars Typhimurium and Newport. Plasmid Journal. 63:150-154. Interpretive Summary: Bacterial foodborne pathogens that are resistant to multiple antibiotics pose serious public and animal health concerns. The antibiotic resistance genes are often transferred among bacteria, through mobile genetic elements such as plasmids (extrachromosomal circular DNA molecules), bacteriophages (viruses that infect bacteria), and transposable elements (DNA fragments that are able to move from one DNA site to another). Three different Salmonella strains were found to harbor small (3-6 kilobase pairs) plasmids carrying genes responsible for kanamycin resistance, Kanamycin is a broad-spectrum aminoglycoside antibiotic that is used to treat various bacterial infections. DNA sequences of the resistant plasmids were determined and analyzed, revealing that they belong to the same plasmid family. Molecular methods employing PCR (polymerase chain reaction) are being developed to detect these plasmids. This study will increase our understanding of antibiotic resistance gene transfer mechanisms, thus enabling us to design effective strategies to prevent the dissemination of the resistance genes and plasmids
Technical Abstract: Multi-antibiotic resistant (MR) Salmonella enterica serovars Typhimurium and Newport are an increasing concern in human and animal health. Many strains are known to carry antibiotic resistance determinants on multiple plasmids, yet detailed information is scarce. Three plasmids conferring kanamycin (Kan) resistance were isolated and sequences were determined. Two Kan-resistant plasmids from S. Newport strains, pSN11/00Kan and pSN02/01Kan, were found to be identical and were 5,698 bp in length. Plasmid pG7601Kan from S. Typhimurium phage type U302 strain G7601 was 3,208 bp, and was the same as the previously reported pU302S from another U302 strain G8430. All three plasmids carried identical aph(3')-I genes. The plasmids were ColE1-like, containing RNA I/RNA II and the rom gene. Plasmids pSN11/00Kan and pSN02/01Kan also carried mobilization genes, mobC and mobABD, similar to those of the pColK-K235 and pColD157 plasmids from the colicinogenic E. coli strains. All three plasmids were stable without kanamycin selection for ~100 generations.