Transferable plasmids of Salmonella enterica associated with antibiotic resistance genes

Authors: McMillan, Elizabeth; Frye, Jonathan; Jackson, Charlene

Submitted to: Frontiers in Microbiology
Publication Type: Review Article
Publication Acceptance Date: 9/17/2020
Publication Date: 10/8/2020
Citation: Mcmillan, E.A., Frye, J.G., Jackson, C.R. 2020. Transferable plasmids of Salmonella enterica associated with antibiotic resistance genes. Frontiers in Microbiology. 11:e562181. https://doi.org/10.3389/fmicb.2020.562181.
DOI: https://doi.org/10.3389/fmicb.2020.562181

Interpretive Summary: Salmonella enterica is one of the most common causes of food-borne illness in the United States and around the world. An increasing number of these infections are resistant to antibiotics and many of the genes responsible for these resistances are carried by plasmids. Conjugative plasmids are independently mobile. Mobilizable plasmids can be transferred to a new cell by a helper plasmid. Thus, plamids can increase the spread of these genes whether they are conjugative or not. It is important to understand the differences in plasmids to determine the effect they have on the spread of antibiotic resistance genes. In this review, we cover the most common incompatibility groups associated with Salmonella enterica focusing on the transfer mechanisms and the associated antibiotic resistance genes. Incompatibility groups reviewed include IncA, IncC, IncF, IncI1, IncHI, IncX, IncN, IncQ1, IncR, and mosaic plasmids. Among these groups are many plasmids present in Salmonella that have caused outbreaks in humans and those that are frequently isolated from animals. These groups differ in their transfer mechanisms, essential genes for transfer, accessory genes, and antibiotic resistance genes. This review serves as a resource to those studying plasmids and the impact they have on the spread of antibiotic resistance.

Technical Abstract: Salmonella enterica is a common foodborne illness in the United States and globally. An increasing number of Salmonella infections are resistant to antibiotics and many of the genes responsible for those resistances are carried by plasmids. Plasmids are important mediators of horizontal gene exchange, which could potentially increase the spread of antibiotic resistance genes. Twenty-eight different incompatibility groups of plasmids have been described in Enterobacteriaceae. Incompatibility groups differ in their accessory gene content, replication mechanisms, and their associations with Salmonella serotypes and animal sources. Plasmids also differ in their ability to conjugate or be mobilized, essential genes, and conditions required for transfer. It is important to understand the differences in gene content and transfer mechanisms to accurately determine the impact of plasmids on the dissemination and persistence of antibiotic resistance genes. This review will cover the most common plasmid incompatibility groups associated with Salmonella enterica with a focus on the transfer mechanisms and associated antibiotic resistance genes.