Project description:Salmonella Heidelberg is currently the 9th common serovar and has more than twice the average incidence of blood infections in Salmonella. A recent Salmonella Heidelberg outbreak in chicken infected 634 people during 2013-2014, with a hospitalization rate of 38% and an invasive illness rate of 15%. While the company’s history suggested longstanding sanitation issues, the strains’ characteristics which may have contributed to the outbreak are unknown. We hypothesized that the outbreak strains of S. Heidelberg might possess enhanced stress tolerance or virulence capabilities. Consequently, we obtained nine food isolates collected during the outbreak investigation and several reference isolates and tested their tolerance to processing stresses, their ability to form biofilms, and their invasiveness in vitro. We further performed RNA-sequencing on three isolates with varying heat tolerance to determine the mechanism behind our isolates’ enhanced heat tolerance. Ultimately, we determined that (i) many Salmonella Heidelberg isolates associated with a foodborne outbreak have enhanced heat resistance (ii) Salmonella Heidelberg outbreak isolates have enhanced biofilm-forming ability under stressful conditions, compared to the reference strain (iii) exposure to heat stress may also increase Salmonella Heidelberg isolates’ antibiotic resistance and virulence capabilities and (iv) Salmonella Heidelberg outbreak-associated isolates are primed to better survive stress and cause illness. This data helps explain the severity and scope of the outbreak these isolates are associated with and can be used to inform regulatory decisions on Salmonella in poultry and to develop assays to screen isolates for stress tolerance and likelihood of causing severe illness.
Project description:Multidrug-resistant (MDR; resistance to >3 antimicrobial classes) Salmonella enterica serovar I 4,[5],12:i:- strains were linked to a 2015 foodborne outbreak from pork. Strain USDA15WA-1, associated with the outbreak, harbors an MDR module and the metal tolerance element Salmonella Genomic Island 4 (SGI-4). Characterization of SGI-4 revealed that conjugational transfer of SGI-4 resulted in the mobile genetic element (MGE) replicating as a plasmid or integrating into the chromosome. Tolerance to copper, arsenic, and antimony compounds was increased in Salmonella strains containing SGI-4 compared to strains lacking the MGE. Following Salmonella exposure to copper, RNA-seq transcriptional analysis demonstrated significant differential expression of diverse genes and pathways, including induction of numerous metal tolerance genes (copper, arsenic, silver, and mercury). Evaluation of swine administered elevated concentrations of zinc oxide (2,000 mg/kg) and copper sulfate (200 mg/kg) as an antimicrobial feed additive (Zn+Cu) in their diet for 4 weeks prior to and 3 weeks post-inoculation with serovar I 4,[5],12:i:- indicated that Salmonella shedding levels declined at a slower rate in pigs receiving in-feed Zn+Cu compared to control pigs (no Zn+Cu). The presence of metal tolerance genes in MDR Salmonella serovar I 4,[5],12:i:- may provide benefits for environmental survival or swine colonization in metal-containing settings.
Project description:The unprecedented magnitude of the 2013-2016 Makona Ebola virus (M-EBOV) epidemic likely resulted from multiple epidemiologic factors that set it apart from previous outbreaks. Nonetheless, genetic adaptations that distinguish M-EBOV from previous isolates may also have contributed to the scale of the epidemic. Of particular interest is a M-EBOV glycoprotein (GP) variant, GP-A82V, that was first detected at the inflection point of the 2013-2016 outbreak - when the number of cases increased exponentially - and which completely supplanted the earlier M-EBOV sequence. We found that, as compared with the earlier strain, GP-A82V increased the ability of M-EBOV to fuse with and infect cells of primate origin, including human blood dendritic cells, without altering innate immune signaling in target cells. Residue 82 is located at the NPC1-binding site on M-EBOV GP and the increased infectivity of GP-A82V was restricted to cells from species in which the NPC1 orthologue bears primate-defining residues at the critical interface. We utilized HIV-derived lentiviral vectors pseudotyped with founder and A82V containing M-EBOV GPs to explore the potential that this modification alters how human monocyte-derived dendritic cells (MDDCs) respond to EBOV GP stimulation.
Project description:Harris County, Texas experienced its largest outbreak of West Nile (WNV) disease in 2014. Characterization WNV isolates from the outbreak using next generation sequencing approaches, phylogeny, and animal studies revealed a novel genotype characterized by selection of an amino acid substitution, NS2A-R188K. Retrospective analysis of Genbank showed this genotype was first identified in New York and Connecticut in 2008 and then in Texas subsequently. Thus, we have termed this the Northeast 2008 (NE/WN08) genotype. Emergence of this genotype in Texas likely involved the displacement of the SW/WN03 genotype. Quasispecies diversity revealed significant variation occurred among viral isolates, but no phenotypic changes were observed in terms of temperature sensitivity and mouse virulence, suggesting that despite WNV being in North America for 15 years there are strong mutational robustness among naturally occurring WNV isolates. Examination of Genbank showed that convergent evolution of NS2A-R188K was also taking place worldwide.