A European-wide dataset to uncover adaptive traits of Listeria monocytogenes to diverse ecological niches.

Listeria monocytogenes (Lm) is a ubiquitous bacterium that causes listeriosis, a serious foodborne illness. In the nature-to-human transmission route, Lm can prosper in various ecological niches. Soil and decaying organic matter are its primary reservoirs. Certain clonal complexes (CCs) are over-represented in food production and represent a challenge to food safety. To gain new understanding of Lm adaptation mechanisms in food, the genetic background of strains found in animals and environment should be investigated in comparison to that of food strains. Twenty-one partners, including food, environment, veterinary and public health laboratories, constructed a dataset of 1484 genomes originating from Lm strains collected in 19 European countries. This dataset encompasses a large number of CCs occurring worldwide, covers many diverse habitats and is balanced between ecological compartments and geographic regions. The dataset presented here will contribute to improve our understanding of Lm ecology and should aid in the surveillance of Lm. This dataset provides a basis for the discovery of the genetic traits underlying Lm adaptation to different ecological niches.

Prevalence and Serotype Diversity of Salmonella enterica in the Estonian Meat Production Chain in 2016-2020.

BACKGROUND: Salmonella enterica represents a considerable public concern worldwide, with farm animals often recognised as an important reservoir. This study gives an overview of the prevalence and serotype diversity of Salmonella over a 5-year period in the meat production chain in Estonia. Data on human salmonellosis over the same period are provided. METHODS: Salmonella surveillance data from 2016 to 2020 were analysed. RESULTS: The prevalence of Salmonella at the farm level was 27.7%, 3.3% and 0.1% for fattening pigs, cattle and poultry, respectively. S. Derby was the most prevalent serotype at the farm level for fattening pigs and S. Dublin for cattle. The top three serotypes isolated at the slaughterhouse and meat cutting levels were S. Derby, monophasic S. Typhimurium and S. Typhimurium with proportions of 64.7%, 9.4% and 7.0%, respectively. These serotypes were the top five most common Salmonella serotypes responsible for human infections in Estonia. S. Enteritidis is the main cause (46.9%) of human salmonellosis cases in Estonia, but in recent years, Enteritidis has not been detected at the slaughterhouse or meat cutting level. CONCLUSION: In recent years, monophasic S. Typhimurium has become epidemiologically more important in Estonia, with the second-highest cause in human cases and third-highest among the most prevalent serotypes of Salmonella enterica in the meat chain.

Prevalence and Numbers of Listeria monocytogenes in Various Ready-to-Eat Foods over a 5-Year Period in Estonia.

HIGHLIGHTS: This study is a significant contribution to L. monocytogenes risk analysis. L. monocytogenes was found in 3.6% of 30,016 analyzed RTE food samples. A food safety criterion of 100 CFU/g was exceeded for 0.3% of the RTE food samples. Salted and cold-smoked fish products were found to be potentially high-risk foods.

Phenogenotypic Characterization of Escherichia coli O157:H7 Strains Isolated from Cattle at Slaughter.

Shiga toxin-producing Escherichia coli (STEC) O157:H7 was isolated from 30 (4%) of 744 cattle hide swab samples collected at Estonian slaughterhouses within a 3-year monitoring program of zoonotic pathogens. The isolates were characterized by determining the presence of STEC main virulence factors, the antimicrobial resistance profiles, and the genetic relatedness by pulsed-field gel electrophoresis (PFGE). Thirteen strains carried the stx2 gene alone and 17 both the stx1 and stx2 genes. The most frequently detected stx subtype was stx2c, occurring alone (n = 12) or in combination with subtype stx1a (n = 13). All isolates harbored the intimin-coding eae gene and produced enterohemolysin. Twelve isolates (40%) showed resistance to at least one of the 14 antimicrobials and the isolates were predominantly resistant to streptomycin, sulfamethoxazole, and ampicillin. No extended-spectrum beta-lactamase-producing isolates were detected. PFGE characterization of the isolates showed an overall similarity higher than 75%, and four clusters based on 100% similarity were revealed.