Evaluation of the Genetics and Functionality of Plasmids in Incompatibility Group I1-PositiveSalmonella enterica

Abstract

Salmonella is a predominant foodborne pathogen in the United States and other countries. Mobile genetic elements such as plasmids allow Salmonella to adapt to external stress factors such as nutrient deprivation and host factors. Incompatibility group I1 (IncI1) plasmid-carrying Salmonella enterica strains were examined to determine the presence of plasmid-associated genes and their influence on phenotypic characteristics. The objective of this study was to understand the genetic determinants on IncI1 plasmids and their impact on antimicrobial susceptibility, competitive growth inhibition of Escherichia coli, and plasmid transfer. Primers were designed for genes that play a role in virulence, antimicrobial resistance, and plasmid transfer based on previously sequenced IncI1 plasmids. Polymerase chain reaction assays were conducted on 92 incompatibility group I1 (IncI1)-positive S. enterica strains. Phenotypic characterization included conjugation assays, antimicrobial susceptibility testing, and bacteriocin production based on the inhibition of growth of colicin-negative E. coli J53. The antimicrobial resistance genes aadA1, tetA, sul1, and bla were detected in 88%, 87%, 80%, and 48% of the strains, respectively. Over half of the strains were resistant or intermediately resistant to streptomycin (85%), sulfonamides (76%), tetracycline (74%), and ampicillin (68%) and 57% of the strains inhibited growth of E. coli J53 strain. Among putative virulence genes, colicin-associated colI and cib were detected in 23% and 35% of strains and imm and ccdA were present in 58% and 54% of strains, respectively. Approximately 61% of strains contained plasmids that conjugally transferred antimicrobial resistance, including 83% where the recipient received IncI1 plasmids. Most of the strains carried an assortment of transfer associated (pil and tra) genes with between 63% and 99% of strains being positive for individual genes. Taken together the study affirms that IncI1 plasmids likely play roles in the dissemination of antimicrobial resistance and virulence-associated factors among enteric organisms.

Pathogenicity and Competitive Fitness of Salmonella enterica Serovar 4,[5],12:i:- Compared to Salmonella Typhimurium and Salmonella Derby in Swine

“…Resistance to ceftiofur in the S. Typhimurium isolate was likely mediated by bla CMY , which has been previously associated with the IncI1 plasmid which was also identified via whole genome sequencing in this isolate (58). In theory it is possible that transfer of these AMR genes may have occurred between our isolates in vivo, however, further investigation would be necessary to definitively prove that the bla CMY gene was indeed located on this plasmid and determine if conjugative transfer genes such as tra or pil were present on same plasmid which would make the possibility of transfer more likely (58). Of the two resistance genotypes utilized for differentiation in this study, it is much more likely that exchange of plasmidassociated genes such as bla CMY could have occurred rather than exchange of genes believed to be chromosomally-located.…”

“…Further investigation of the genotypic antimicrobial resistance genes present in the isolates suggests that the resistance to gentamicin in the S. 4, [5],12:i:-isolate was likely mediated through the strA/strB genes which have been shown to be frequently inserted into the chromosome in S. 4, [5],12:i:-ASSuT resistant isolates (48,49). Resistance to ceftiofur in the S. Typhimurium isolate was likely mediated by bla CMY , which has been previously associated with the IncI1 plasmid which was also identified via whole genome sequencing in this isolate (58). In theory it is possible that transfer of these AMR genes may have occurred between our isolates in vivo, however, further investigation would be necessary to definitively prove that the bla CMY gene was indeed located on this plasmid and determine if conjugative transfer genes such as tra or pil were present on same plasmid which would make the possibility of transfer more likely (58).…”

Identification of Genes Involved in Antifungal Activity of Burkholderia seminalis Against Rhizoctonia solani Using Tn5 Transposon Mutation Method

“…In agreement with the results of this study, Coplin et al (1989) reported that the plasmid was able to encode an antagonistic protein [ 31 ]. In addition, it has been reported that with the help of the plasmid, bacteria were able to obtain new phenotypes such as antibiotic resistance, pathogenicity and metabolic capacity [ 32 , 33 ].…”

The Salmonella enterica Plasmidome as a Reservoir of Antibiotic Resistance

“…The three most frequent ORIs identified in Salmonella isolates, excluding the 851 putative ORIs, were the transferable IncFII (n isolate = 533), IncFIB (n isolate = 371), and IncI (n isolate = 142) ( Table 1). All three Inc group plasmids have been shown to carry virulence-associated and AMR genes within Enterobacteriaceae [14,[27][28][29][30]. The majority of the IncFII and IncFIB ORIs were identified from S. Enteritidis and S. Typhimurium (Table 1) (at 33% and 28% for IncFII and at 47% and 39% for IncFIB, respectively).…”