Antimicrobial resistant plasmid effects on Salmonella enterica serotype Heidelberg

Thumbnail Image
Friesen-Enns, Jayelle
Journal Title
Journal ISSN
Volume Title
Salmonella enterica serotype Heidelberg is the third most frequently isolated serotype in Canada and is of particular interest due to its resistance to cephalosporin-class antimicrobials. Through national surveillance of Canadian S. Heidelberg strains isolated from poultry sources and human infections, we previously demonstrated that human and animal-derived isolates were genetically similar (ST15) and that structurally similar IncI1 plasmids harbouring the blaCMY-2 gene were predominantly responsible for cephalosporin-resistance. Here, we focus on the impact of two variants (pCMYN13-02944A and pCMY12-2460C) of a well-characterized and widely disseminated IncI1plasmid on the core physiology of an S. Heidelberg strain isolated from Canadian national surveillance. The plasmids were transferred via conjugation to a susceptible and previously whole-genome sequenced (WGS) S. Heidelberg isolate (N13-01291) to form isogenic strain pairs. Illumina WGS was performed on the parent and transconjugants to monitor genetic alteration introduced during conjugation. Plasmid maintenance and viability were assessed using the PMAxx™ (Biotum, Inc., Hayward, CA, USA) photoreactive viability dye followed by quantitative polymerase chain reaction (PCR). Growth curves and Biolog Omnilog (Biolog, Hayward, CA, USA) phenotypic microarrays were performed to analyze the effects of the plasmids of interest on fitness and growth kinetics. The presence of either plasmid resulted in observable changes in growth kinetics compared to N13-01291. Biofilm assays were performed using 0.1% (w/v) crystal violet staining which determined that N13-01291, N13-01291/pCMYN13-02944A, and N13-01291/pCMY12-2460C are poor biofilm producers. Phylogenomic analysis of the isogenic strain pairs indicated the presence of a shared single nucleotide variant (SNV) and a unique SNV in the presence of either plasmid which affected various changes in growth kinetics. Proteomics were analysed using tandem mass tags and LC- MS/MS analysis. In the presence of one plasmid (pCMYN13-02944A), there were 341 significantly detected proteins that had a log2-fold change ≥ 1 and 72 that had a log2-fold change ≥ 2. In the presence of plasmid (pCMY12-2460C), there were 415 significantly detected proteins that had a log2-fold change ≥ 1 and 96 proteins that had a log2-fold change ≥ 2. In conclusion, the presence of either IncI1 plasmid influenced changes in growth and proteomic expression when present in the host isolate N13-01291.
Antimicrobial resistance, Salmonella, Plasmid, Enterobacterales, Heidelberg, Proteomics, Whole-genome sequencing, Growth assays