Evaluation of Incompatibility Group I1 (IncI1) Plasmid-Containing Salmonella enterica and Assessment of the Plasmids in Bacteriocin Production and Biofilm Development

Abstract

Mobile genetic elements, such as plasmids, can potentially increase the ability of bacteria to infect and persist in vertebrate host cells. IncI1 plasmids are widely distributed in Salmonella from food animal sources and associated with clinically important strains. These plasmids often encode antimicrobial resistance; however, little is known about their impact on the virulence of Salmonella strains. To assess the potential impact of the plasmids on virulence, 43 IncI1-positive Salmonella isolates from human and animal sources were subjected to whole genome sequence (WGS) analyses and evaluated for their abilities to invade and persist for 48 h in Caco-2 human intestinal epithelial cells, form biofilms and encode bacteriocins. Draft WGS data were submitted to predict the presence of virulence and antimicrobial resistance genes, plasmid replicon types present, conduct plasmid multilocus sequence typing (pMLST), and core genome MLST (cgMLST) in the isolates. Caco-2 cells were infected with Salmonella strains and incubated for both one and 48 h for the invasion and persistence assays, respectively. Additionally, Salmonella isolates and IncI1 plasmid carrying transconjugants (n = 12) generated in Escherichia coli were assessed for their ability to produce biofilms and bacteriocin inhibition of growth of other bacteria. All Salmonella isolates infected Caco-2 cells and persisted in the cells at 48 hrs. Persistent cell counts were observed to be significantly higher than invasion assay cell counts in 26% of the isolates. Among the IncI1 plasmids, there were 18 pMLST types. Nearly 35% (n = 15) of Salmonella isolates produced biofilms; however, none of the IncI1-positive transconjugants produced increased biofilms compared to the recipient. Approximately 65% (n = 28) of isolates and 67% (n = 8) of IncI1-positive transconjugants were able to inhibit growth of at least one E. coli strain; however, none inhibited the growth of strains from species other than E. coli. The study characterized IncI1 positive Salmonella isolates and provided evidence about the potential contributions of IncI1 plasmids virulence phenotypes and areas where they do not. These findings should allow for more focused efforts to assess the impact of plasmids on bacterial pathophysiology and human health.

Evaluation of Live Bacterial Prophylactics to Decrease IncF Plasmid Transfer and Association With Intestinal Small RNAs

“…Uniquely, a single IncI1 plasmid and salmochelin receptor iroN remained highly conserved in P + V fecal E. coli , and IncI1 in vitro plasmid transfer by isolate IA-EC-001 was largely unaffected by smRNA concentration. The salmochelin operon is commonly found on IncI1 plasmids ( Kaldhone et al, 2019 ), which suggests this conserved IncI1 plasmid may be responsible for this observed- iroN maintenance in P + V isolates. This suggests that intestinal smRNAs specifically target genes on IncF plasmids and do not affect the transfer of IncI1 plasmids.…”

Elucidation of global and local genomic epidemiology ofSalmonella entericaserovar Enteritidis through multilevel genome typing

“…Because plasmids are known to play a key role in the acquisition of drug resistance genes [31, 32], we identified Inc plasmid groups that are likely present in the S. Enteritidis population. Several of these putative plasmids were MDR associated.…”

“…Moreover, we identified multiple plasmids that were MDR associated. Plasmids are known to play a key role in the acquisition of drug resistance genes [28,29]. MDR of African isolates in MGT3-ST10…”

Current knowledge and perspectives of potential impacts of Salmonella enterica on the profile of the gut microbiota

“…The SPI-2 T3SS genes are expressed inside the SCV, resulting in the rapid induction of intestinal inflammation [54]. In addition to SPIs, plasmids, carrying virulence genes, are essential for the infection process to host cells in order to ensure nutrient supply [55], compete against commensal bacteria [56], avoid killing by innate immune system, and manipulate the host to establish infection [57].…”