Title: Characterization and distribution of ColE1-like kanamycin-resistance plasmids in Salmonella enterica from food animals Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 21, 2014
Publication Date: May 17, 2014
Citation: Chen, C., Strobaugh Jr, T.P., Nguyen, L.T., Abley, M., Lindsey, R.L., Cray, P.J. 2014. Characterization and distribution of ColE1-like kanamycin-resistance plasmids in Salmonella enterica from food animals. Meeting Abstract. Technical Abstract: Background: Antimicrobial resistant foodborne pathogens cause public health concerns and multi-drug resistant (MDR) pathogens present difficulties when treatment is warranted. Large plasmids are responsible for the majority of the MDR and subsequently, the focus of most research. Previous studies showed that some Salmonella isolates harbor small ColE1-like plasmids that carry a single aph gene responsible for kanamycin resistance (KANR). However, little is known on the distribution and persistence of these plasmids. Materials: KANR Salmonella isolates (n=224) from food animals collected at slaughter through the 2010-2011 National Antimicrobial Resistance Monitoring System (NARMS) were screened by PCR using ColE1 typing primers. DNA from ColE+ isolates was transformed into Escherichia coli and KANR clones were selected. The resulting plasmids were characterized by restriction mapping and sequencing. Results: Of the 224 KANR Salmonella isolates 29.5% (n=66) tested PCR positive for the ColE1 replicon, and 22 of these plasmids were able to propagate in E. coli. All KANR ColE plasmids carried the aph(3’)-I gene encoding an aminoglycoside phosphotransferase. Restriction mapping showed the three previously characterized major plasmid groups A (n=7), B (n=6), and C/C3 (n=3), plus two new plasmid groups: X (n=3) and Y/Y2/Y3 (n=3). Sixteen (72.7%) of the plasmid-carrying isolates were from turkey and included all the X and Y plasmid groups. Serotype Hadar (n=6) comprised of >27% of the strains carrying KANR ColE plasmids; all group X plasmids were in serotype Hadar. Serotype Senftenberg carried all of the group Y and one group B plasmid. Typhimurium (n=4) isolates carried group A plasmids. Newport (n=3) isolates each carried a different plasmid group (A, B, or C). Other plasmid-containing serotypes include Schwarzengrund (2), Brandenburg (1), Orion (1), and I 4,12:I,v: (1). Conclusion: KANR ColE1-like plasmids are widely distributed among different Salmonella serotypes. Turkey was the most common animal source for Salmonella strains carrying KANR ColE1-like plasmids in the 2010-2011 NARMS samples. This underscores the importance of monitoring small plasmids carrying antimicrobial resistance genes in addition to the large MDR plasmids.