Determination of the prevalence of resistance to biocides in Salmonella and identification of the genetic mechanisms of resistance

Description

The project goal is to determine if food animal isolates of the top ten Salmonella serovars associated with human infections are resistant to chemical antimicrobial interventions used in processing. The resistance elements found in serovars associated with human infections will be compared to those found in serovars associated with animals to determine if some chemical interventions used during processing may be selecting for the serovars that most often cause human infections.

Objectives:

Objective 1: Screen isolates of Salmonella serovars most often associated with human infection for resistance to antimicrobials, sanitizers, and biocides used as interventions.

Objective 2: Compare genome sequences of resistant isolates to susceptible isolates to identify resistance mechanisms. Determine if these resistance mechanisms are linked to antibiotic resistance, or virulence genes, or if they are associated to outbreak strains.

Objective 3: Determine if genetic elements encoding the resistance could be used as markers to identify biocide resistant strains of Salmonella.
 

800 isolates of Salmonella will be screened for resistance to compounds used as interventions. These isolates will be from the top ten serovars found in human infections and the top ten most often associated with beef, chicken, swine, and turkeys. The isolates will be chosen from our National Antimicrobial Resistance Monitoring System (NARMS) collection of over 50,000 Salmonella. Researchers will use a broth micro-dilution assay to detect increased levels of resistance. From the isolates found to be biocide resistant, 36 will be chosen for whole genome sequencing followed by bioinformatics analyses to identify genes encoding known resistance mechanisms or identify sequence mutations that may lead to resistance. Any linkage to other genetic elements such as antibiotic resistance or virulence will then be determined. Unique sequences will be used as markers of resistance.