T2-05 Characterization of Multidrug-resistant Salmonella Typhimurium and Salmonella Kentucky Strains Recovered from Chicken Carcasses Using Genotypic and Phenotypic Methods

Monday, July 10, 2017: 9:30 AM
Room 16 (Tampa Convention Center)
Salina Parveen , University of Maryland Eastern Shore , Princess Anne , MD
Rizwana Tasmin , University of Maryland Eastern Shore , Princess Anne , MD
Nur Hasan , CosmosID , Rockville , MD
Christopher Grim , U.S. Food and Drug Administration, CFSAN , Laurel , MD
Arquette Grant , Univerisity of Maryland Eastern Shore , Princess Anne , MD
Seon Choi , University of Maryland-College Park , College Park , MD
Mohammad Alam , U.S. Food and Drug Administration, CFSAN , Laurel , MD
Rebecca Bell , U.S. Food and Drug Administration , College Park , MD
Christopher Cavanaugh , U.S. Food and Drug Administration , Laurel , MD
Kannan Balan , U.S. Food and Drug Administration, CFSAN , Laurel , MD
Uma Badu , U.S. Food and Drug Administration , Laurel , MD
Introduction: Salmonella Typhimurium (ST) is the leading cause of human non-typhoidal gastroenteritis in the United States. Salmonella Kentucky (SK) is one the most commonly recovered serovars from processed poultry carcasses. Considerable knowledge gaps still exist regarding the biology of multidrug resistant (MDR) ST and SK.

Purpose:  The purpose of this study was to investigate the genotypic and phenotypic characteristics of ST and SK recovered from commercially processed chicken carcasses using whole genome sequencing, phenotype microarray, and intracellular killing assays.

Methods:  One MDR ST (ST221_31B) and one MDR SK (SK222_32B) strain were sequenced using an Illumina MiSeq and compared with 28 previously sequenced Salmonella genomes. For phenotypic variation, 980 metabolic conditions were tested using the Biolog phenotypic microarray. Intracellular killing assays were conducted using chicken and murine macrophages.

Results:  Phylogenetic analysis employing homologous alignment of a 1,185 non-duplicated protein-coding core genome demonstrated fully resolved, bifurcating patterns with varying levels of diversity and separated both ST and SK into distinct monophyletic serovar-specific clades. Single nucleotide polymorphism (SNP) analysis identified 1,911 SNPs within ST and 176 SNPs within SK strains. In addition to serovar-specific conserved coding sequences, the genomes of ST and SK harbor several genomic regions with significant genetic differences. These included phage and phage-like elements, carbon utilization or transport operons, fimbriae operons, putative membrane-associated protein-encoding genes, antibiotic resistance genes, siderophore operons, and numerous hypothetical protein-encoding genes. ST was capable of utilizing certain carbon compounds more efficiently than SK. ST survived for 48 h in macrophages, while SK was mostly eliminated. A three-fold growth of ST was observed in chicken granulosa cells, while SK was unable to replicate in these cells.

Significance: These results demonstrated that ST can survive host defenses better and is more invasive than SK and provided some insights into the genomic determinants responsible.