Drug-resistant Salmonella serovar Enteritidis genome sequenced by experts

Scientists from North Carolina State University sequenced the genome of a virulent Salmonella Enteritidis strain that affected two poultry flocks in consecutive years and discovered that it was both antibiotic-resistant and could affect people.

Salmonella colonies. Image Credit: North Carolina State University.

Characterization of the strain, named SE_TAU19, will help public health agencies in tracking outbreaks and avoiding exposures.

Two species of Salmonella exist and one of these, Salmonella enterica, is involved in human disease. S. enterica has over 2,500 serovars, or groups of bacteria, most of which could cause disease in humans. Salmonella serovar Enteritidis (SE) is generally linked with poultry and is the major cause of human illness around the world.

The majority of the Salmonella infections in humans are foodborne, and several animals—like chickens—can harbor the pathogen without themselves getting sick. The ability of SE_TAU19 to induce clinical disease in poultry fascinated Grayson Walker, a combined DVM and Ph.D. student in Luke Borst’s laboratory at NC State’s College of Veterinary Medicine and first author of a paper describing the study.

We usually think of Salmonella as harbored by chickens without harming them; however, this strain was virulent and actually made them sick. We also know that Salmonella likes to stick around. This strain killed broiler chickens throughout the growing period and recurred one year later in a different flock. So, we decided to sequence the genome and see which resistance and virulence features made the strain unique.”

Grayson Walker, Study First Author and Student, College of Veterinary Medicine, North Carolina State University

The researchers sequenced the genome of the strain and discovered that the genome included seven antimicrobial resistance genes, 120 virulence genes, and a huge virulence plasmid. Plasmids are “swappable” genetic elements that can be transferred between strains to make them more infectious or antibiotic-resistant.

While we cannot say that it is a ‘new’ strain of Salmonella, we can say that not only is this strain deadly to poultry, antibiotic resistant and infectious but also that it could infect humans. The good news is that by sequencing the genome we now have data that could help pinpoint the origin of and contain any future outbreaks.”

Grayson Walker, Study First Author and Student, College of Veterinary Medicine, North Carolina State University

The study was published in Frontiers in Veterinary Science journal and is supported by the U.S. Department of Agriculture Animal Plant Health Inspection Service’s National Bio and Agro-defense Facility Scientist Training Program.

Whole-genome sequencing was accomplished by the FDA GenomeTrakr program funded under grant 1U18FD00678801 in the lab of co-author Sid Thakur, professor of population health and pathobiology and the director of NC State’s and the College of Veterinary Medicine’s Global Health programs. Borst, associate professor of veterinary anatomic pathology at NC State, is the corresponding author.