Detection of colistin resistance mcr-1 gene in Salmonella enterica serovar Rissen isolated from mussels, Spain, 2012- to 2016.

Nineteen Salmonella strains were isolated from 5,907 randomly selected mussel samples during a monitoring programme for the presence of Salmonella in shellfish in Galicia, north-west Spain (2012-16). Serovars, sequence type and antimicrobial resistance genes were determined through genome sequencing. Presence of the mcr-1 gene in one strain belonging to serovar Rissen and ST-469 was identified. The mcr-1 gene had not been isolated previously in environmental Salmonella isolated from mussels in Spain.

An Evaluation of the Pathogenic Potential, and the Antimicrobial Resistance, of Salmonella Strains Isolated from Mussels.

Salmonella spp. and antimicrobial resistant microorganisms are two of the most important health issues worldwide. In the present study, strains naturally isolated from mussels harvested in Galicia (one of the main production areas in the world), were genetically characterized attending to the presence of virulence and antimicrobial resistance genes. Additionally, the antimicrobial profile was also determined phenotypically. Strains presenting several virulence genes were isolated but lacked all the antimicrobial resistance genes analyzed. The fact that some of these strains presented multidrug resistance, highlighted the possibility of bearing different genes than those analyzed, or resistance based on completely different mechanisms. The current study highlights the importance of constant surveillance in order to improve the safety of foods.