Serotypes and Antimicrobial Resistance in Salmonella enterica Recovered from Clinical Samples from Cattle and Swine in Minnesota, 2006 to 2015

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.

Inferring source attribution from a multiyear multisource data set of Salmonella in Minnesota

“…Information on Salmonella isolates of food animal (cattle, swine, poultry) origin isolated by the Minnesota Veterinary Diagnostic Laboratory (MVDL) from diagnostic submissions between 2006 and 2015 was also collected. A detailed description of the MVDL database and cattle and swine isolates is available elsewhere (Hong et al., ). Finally, data on the relative frequency of Salmonella serotypes stratified per meat product (chicken, ground turkey, ground beef, pork chop) from various retail locations in Minnesota that were collected as part of the FoodNet/National Antimicrobial Resistance Monitoring System (NARMS) Retail Food Study between 2002 and 2013 were provided by MDH.…”

“…Information on Salmonella isolates of food animal (cattle, swine, poultry) origin isolated by the Minnesota Veterinary Diagnostic Laboratory (MVDL) from diagnostic submissions between 2006 and 2015 was also collected. A detailed description of the MVDL database and cattle and swine isolates is available elsewhere (Hong et al, 2016).…”

Pathogenicity and Competitive Fitness of Salmonella enterica Serovar 4,[5],12:i:- Compared to Salmonella Typhimurium and Salmonella Derby in Swine

“…More recently, however, S. 4, [5],12:i:-has been increasingly identified worldwide in humans, swine, cattle, and poultry (4,6,7). In fact, S. 4, [5],12:i:-has been documented to be more common than S. Typhimurium in the U.S. swine population based on data from the National Veterinary Services Laboratory (NVSL) and the Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL) since 2014 (6)(7)(8). Although S. 4, [5],12:i:has been reported more frequently, additional research is needed to evaluate the specifics of its pathogenicity in swine.…”

“…The rise in prevalence of Salmonella 4, [5],12:i:-in livestock and humans also raises the question of why the serovar has recently emerged and become increasingly prevalent. Salmonella 4, [5],12:i:-has repeatedly been reported to be more highly resistant to antimicrobials relative to S. Typhimurium (6,31,32), which may provide a significant advantage to its survival in swine operations with extensive antimicrobial drug use. Likewise, S. 4, [5],12:i:-is commonly resistant to heavy metals such as zinc and copper, which can be added to livestock feeds as an alternative to antibiotics to reduce bacterial infections (16,33).…”

Muramyl endopeptidase Spr contributes to intrinsic vancomycin resistance inSalmonella entericaserovar Typhimurium

“…Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gramnegative enterobacterium with an increasing antibiotic resistance development in its genus (Klemm et al 2018;Hong et al 2016;Angelo et al 2016). As the S. Typhimurium genome includes genes with high sequence similarity to the mepS, mepM and mepH genes of E. coli, and given the potential importance of mepS and mepM for viability of E. coli (Singh et al 2012), we studied the phenotypes of S. Typhimurium mutants in which these genes were deleted, either singly or in combination.…”