Monitoring Salmonella resistance to antimicrobials in Minnesota during the past 9 years

The STEMMA laboratory at the University of Minnesota and more particularly Dr. Alvarez’s team is aiming at monitoring of antimicrobial resistance in animal and human bacteria. Therefore, the research they present in this article published this month, focused on Salmonella species both in swine and cattle. Records from the Veterinary Diagnostic Laboratory between 2006 and 2015 were compiled to study the evolution of the proportion of resistant strains of Salmonella in Minnesota.

Dr Hong, in collaboration with researchers from the U of MN, captured the number and the type of antimicrobials each strain was resistant to. He also monitored the evolution of the resistances over the nine-year period.

Evolution in antimicrobial resistant Salmonella isolates
recovered from swine at the MVDL in 2006–2015.

Explanation of the figure: Proportion of Salmonella isolates recovered from swine samples that were resistant to ampicillin (A), ceftiofur (C), enrofloxacin (E), florfenicol (F), gentamicin (G), neomycin (N), oxytetracycline (O), sulfadimethoxine (Sul), spectomycin (Sp) and trimethorpim/ sulfamethoxazole (Ts)

Abstract: Salmonellosis remains one of the leading causes of foodborne disease worldwide despite preventive efforts at various stages of the food production chain. The emergence of multi-drug resistant (MDR) non-typhoidal Salmonella enterica represents an additional challenge for public health authorities. Food animals are considered a major reservoir and potential source of foodborne salmonellosis; thus, monitoring of Salmonella strains in livestock may help to detect emergence of new serotypes/MDR phenotypes and to gain a better understanding of Salmonella epidemiology. For this reason, we analyzed trends over a nine-year period in serotypes, and antimicrobial resistance, of Salmonella isolates recovered at the Minnesota Veterinary Diagnostic Laboratory (MVDL) from swine (n = 2,537) and cattle (n = 1,028) samples. Prevalence of predominant serotypes changed over time; in swine, S. Typhimurium and S. Derby decreased and S. Agona and S. 4,5,12:i:- increased throughout the study period. In cattle, S. Dublin, S. Montevideo and S. Cerro increased and S. Muenster became less frequent. Median minimum inhibitory concentration (MIC) values and proportion of antibiotic resistant isolates were higher for those recovered from swine compared with cattle, and were particularly high for certain antibiotic-serotype combinations. The proportion of resistant swine isolates was also higher than observed in the NARMS data, probably due to the different cohort of animals represented in each dataset. Results provide insight into the dynamics of antimicrobial resistant Salmonella in livestock in Minnesota, and can help to monitor emerging trends in antimicrobial resistance.

Link to the full article

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