ARS | Publication request: Detection of Plasmids and Class 1 Integrons in Salmonella enterica serovar Agona Isolated from NARMS Slaughter Samples Collected in Years 1997 through 2003

Submitted to: Microbial Drug Resistance
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 31, 2007
Publication Date: September 1, 2007
Citation: Douris, A., Cray, P.J., Jackson, C.R. 2007. Detection of Plasmids and Class 1 Integrons in Salmonella enterica serovar Agona Isolated from NARMS Slaughter Samples Collected in Years 1997 through 2003. Microbial Drug Resistance.13(3):212-219.

Interpretive Summary: Currently, there is a lack of published data that examines mobile genetic elements, such as plasmids and integrons, responsible for dissemination of antimicrobial resistance in S. Agona isolates recovered from U.S. food animals. A total of 60 Salmonella enterica serovar Agona isolates from cattle, turkey, chicken and swine submitted to the National Antimicrobial Resistance Monitoring System –Enteric Bacteria (NARMS) from 1997 through 2003 were examined for plasmids and class 1 integrons. Large plasmids (33 kb – 291 kb) were present in 83% of the isolates resistant to five or more antimicrobials; however, 16% of the pan-susceptible isolates also had large plasmids. Presence of large plasmids did not correspond to isolate source or year isolate was recovered but did appear to correspond to XbaI pulsed-field gel electrophoresis (PFGE) patterns. Two sizes of large plasmids appeared most often: 145.4 kb and 97 kb. A type of mobile genetic element, Class 1 integrons, were not detected on plasmids but were detected on the chromosome of 8% (2/25) of the susceptible isolates and 49% (17/35) of the isolates with multiple drug resistance. These data will be useful for researchers for study of dissemination of antimicrobial resistance among Salmonella specifically S. Agona.

Technical Abstract: A total of 60 Salmonella enterica serovar Agona isolates (25 pan-susceptible isolates and 35 isolates resistant to five or more antimicrobials) submitted to the National Antimicrobial Resistance Monitoring System –Enteric Bacteria (NARMS) from 1997 through 2003 were examined for plasmids and class 1 integrons. Samples originated from cattle, turkey, chicken and swine presented at federally inspected slaughter and processing plants. Large plasmids (33 kb – 291 kb) were present in 83% of the isolates resistant to five or more antimicrobials; however, 16% of the pan-susceptible isolates also had large plasmids. Presence of large plasmids did not correspond to isolate source or year isolate was recovered but did appear to correspond to XbaI PFGE patterns. Two sizes of large plasmids appeared most often: 145.4 kb and 97 kb. Class 1 integrons were not detected on plasmids but were detected on the chromosome of 8% (2/25) of the pan-susceptible isolates and 49% (17/35) of the isolates with multiple drug resistance. Expression of multiple drug resistance among S. Agona isolates occurred regardless of the presence of a class 1 integrons suggesting that plasmids play an equally important role in the development of resistant S. Agona. More research is needed to better understand the mechanisms by which S. Agona acquires, harbors and transfers resistance determinants.