Author(s): Dimarzio M, Shariat N, Kariyawasam S, Barrangou R, Dudley EG
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Abstract Salmonella enterica subspecies enterica serovar Typhimurium is a leading cause of foodborne salmonellosis in the United States. The number of antibiotic resistant isolates identified in humans is steadily increasing, suggesting that the spread of antibiotic resistant strains is a major threat to public health. S. Typhimurium is commonly identified in a wide range of animal hosts, food sources, and environments, but little is known about the factors mediating the spread of antibiotic resistance in this ecologically complex serovar. Previously, we developed a subtyping method, CRISPR-MVLST, which discriminates among strains of several common S. enterica serovars. Here, CRISPR-MVLST identified 22 sequence types within a collection of 76 S. Typhimurium isolates from a variety of animal sources throughout central Pennsylvania. Six of the sequence types were identified in more than one isolate, and we observed statistically significant differences in resistance among these sequence types to 7 antibiotics commonly used in veterinary and human medicine, such as ceftiofur and ampicillin (p<0.05). Importantly, five of these sequence types were subsequently identified in human clinical isolates, and a subset of these isolates had identical antibiotic resistance patterns, suggesting that these subpopulations are transmitting through the food system. Therefore, CRISPR-MVLST is a promising subtyping method for monitoring the farm to fork spread of antibiotic resistance in S. Typhimurium.
This article was published in Antimicrob Agents Chemother
and referenced in Journal of Phylogenetics & Evolutionary Biology