Characterization of Epidemic IncI1-Iγ Plasmids Harboring Ambler Class A and C Genes in Escherichia coli and Salmonella enterica from Animals and Humans

Abstract

The aim of the study was to identify the plasmid-encoded factors contributing to the emergence and spread of epidemic IncI1-I␥ plasmids obtained from Escherichia coli and Salmonella enterica isolates from animal and human reservoirs. For this, 251 IncI1-I␥ plasmids carrying various extended-spectrum ␤-lactamase (ESBL) or AmpC ␤-lactamase genes were compared using plasmid multilocus sequence typing (pMLST). Thirty-two of these plasmids belonging to different pMLST types were sequenced using Roche 454 and Illumina platforms. Epidemic IncI1-I␥ plasmids could be assigned to various dominant clades, whereas rarely detected plasmids clustered together as a distinct clade. Similar phylogenetic trees were obtained using only the plasmid backbone sequences, showing that the differences observed between the plasmids belonging to distinct clades resulted mainly from differences between their backbone sequences. Plasmids belonging to the various clades differed particularly in the presence/absence of genes encoding partitioning and addiction systems, which contribute to stable inheritance during cell division and plasmid maintenance. Despite this, plasmids belonging to the various phylogenetic clades also showed marked resistance gene associations, indicating the circulation of successful plasmid-gene combinations. The variation in traY and excA genes found in IncI1-I␥ plasmids is conserved within pMLST sequence types and plays a role in incompatibility, although functional study is needed to elucidate the role of these genes in plasmid epidemiology.

IncI1 Plasmids Carrying Various bla CTX-M Genes Contribute to Ceftriaxone Resistance in Salmonella enterica Serovar Enteritidis in China

“…Our data revealed that resistance to ceftriaxone in S. Enteritidis is mainly due to the transmission of various IncI1 conjugative plasmids carrying various bla CTX-M genes. Our data corroborate the results of recent studies that these types of plasmids have the potential to be spread in Salmonella and other bacterial species (15,16). Future studies should focus on monitoring the transmission routes and assessing …”

Contemporary IncI1 plasmids involved in the transmission and spread of antimicrobial resistance in Enterobacteriaceae

“…For instance, ST7, ST31, ST37 plasmids show the traY-excA genes of R621a but the inc sequences are 100% identical to that of R64. ST7 has the parAB genes of R64; ST37 has the parAB of R621a; and ST31, instead of parAB genes, has the soj-yfhA genes, previously described as a partitioning system (Smith et al, 2015) (Smet et al, 2010).…”

“…In recent years, plasmids of the IncI1 and IncIγ families have been recognized in clinically relevant bacteria from human, animal and environmental sources (Carattoli, 2009) (Carattoli, 2011). Comparative analysis of fully sequenced plasmids has shown that contemporary IncI1 and IncIγ plasmids have structures consistent with those of historical reference plasmids, including conserved replication, stability, leading and transfer regions (Takahashi et al, 2011) (Smith et al, 2015) (Johnson et al, 2011). Beyond the conserved backbone, most IncI1 and IncIγ plasmids also contain variable regions such as AMR.…”

“…IncI1 was recognized as one of the most pervasive plasmid type in ESBL producers of animal origin (Smith et al, 2015).…”

Use of antibiotics in animals and people

“…A recent study of E coli and Salmonella enterica from the same national collections as used in the study by Wu and others examined epidemic IncI1-Iγ plasmids and found similar plasmid-gene combinations from different animal sources and from humans, which the authors said ‘suggests transmission between animal and human isolates, as was previously assumed’ (Smith and others 2015). Similarly, research in the Netherlands using whole-genome sequencing methods found that genetically unrelated human and animal E coli carried nearly identical plasmids (IncI1- and IncK- types) conferring cephalosporin resistance (de Been and others 2014).…”