MEB participated in the phagocytosis assays and analysis of data and contributed to drafting the manuscript. All authors read and approved the final draft.”
“Background Plasmids have been indispensable tools in the development of molecular biology and much of our understanding of their biology has been based on a small number of model replicon transmissible elements. However, less is known about natural plasmids and in particular, the

interplay between plasmids and their host strains. Bacterial plasmids are widely recognised for their role in the expansion and dissemination of virulence and antibiotic resistance genes selleck kinase inhibitor both between members of the same species and to new bacterial hosts of different species [1, 2]. Their ability to acquire and spread either single or multiple antibiotic resistance genes to pathogens has become a considerable problem and an obstacle to successful therapeutic treatment [3]. This is compounded

by the lack of development of new effective antibiotics, particularly against infections caused by Gram negative bacteria with plasmid mediated antibiotic resistances, which are causing significant global clinical problems [4]. The recent emergence of genes including β-lactamases which confer resistance to the commonly used β-lactam class of antibiotics, can largely be attributed to the spread and persistence selleckchem of successful plasmids in a wide range of bacterial hosts [5–7]. However, despite their importance and the recently generated wealth of plasmid sequence data [8], our knowledge of the factors which allow plasmids to maintain antibiotic resistance genes, to remain stable in bacterial populations in the absence of selective pressure, and to successfully spread to different bacterial strains is very poor. In Loperamide elementary terms the evolutionary success of a plasmid is reliant on (1) the ability to transfer

vertically to daughter cells of the host bacterial strain, therefore remaining stable within this population; and/or (2) the ability to transfer horizontally to alternative bacterial hosts via conjugation [9]. Vertical stability can be ensured by the Cobimetinib presence of an addiction system such as toxin-antitoxin systems [10]; by lack of a fitness cost conferred by the plasmid [11]; by action of an active plasmid partitioning system [12]; and/or by providing beneficial attributes such as antibiotic resistance or adhesive properties to the host providing a competitive advantage [13]. Effective horizontal transmission is associated with the frequency with which a plasmid can pass between strains and become established in a host strain after conjugation under different environmental conditions [14]. Previously, we sequenced and characterised an IncK plasmid, denoted pCT, isolated from scouring calves [15–17]. Although it was initially identified in E. coli animal isolate, the ca.