Don't overlook the little guy: An evaluation of the frequency of small plasmids co-conjugating with larger carbapenemase gene containing plasmids

Katie E Barry,Alexander M Wailan,Anna E Sheppard,Derrick Crook,Kasi Vegesana,Nicole Stoesser,Hardik I Parikh,Robert Sebra,Amy J Mathers

doi:10.1016/j.plasmid.2019.03.005

Abstract

As the spread of antimicrobial resistance (AMR) genes becomes an increasing global threat, improved understanding of mobile genetic elements which contribute to the spread of antimicrobial resistance genes, becomes more critical. We created transconjugants from the mating of three chromosomally isogenic Klebsiella pneumoniae carbapenemase (blaKPC) positive Citrobacter freundii isolates with a laboratory strain of Escherichia coli and evaluated the movement of small cryptic plasmids (SCPs), p3223 and p1916, when larger blaKPC-plasmids were transferred. In all of the 143 transconjugants, multiple plasmids, both large and small, transferred with each mating. When two blaKPC-plasmids were present in the host, frequently (87%; 98/113) both would be transferred during mating. p3223 is found in a wide range of bacterial hosts that harbor AMR genes; p1916 has been identified in only a limited number of publicly available sequences to date. From our evaluation, there is still much to learn about SCPs, and the high rate of co-transfer of multiple plasmids from real-world carbapenemase-producing Enterobacteriales.

Highlights

Carbapenemase-producing Enterobacteriales (CPE) are considered an urgent threat to modern medicine because of increased mortality in infected patients due to the lack of therapeutic options and their rapid emergence globally over the last decade (Center of Disease Control, 2013)
Carbapenemase genes in Enterobacteriales most often reside on mobile genetic elements (MGE), such as plasmids, which can be shared across many species (Sheppard et al, 2016a)
Three C. freundii isolates with closed assemblies were selected for conjugation experiments because they had highly related chromosomes (< 100 single nucleotide variants (SNVs)) and harbored the two same small cryptic plasmids (SCPs), but varied with their remaining plasmid content and organization (Fig. 1 and Supplement Table S1)

Summary

Introduction

Carbapenemase-producing Enterobacteriales (CPE) are considered an urgent threat to modern medicine because of increased mortality in infected patients due to the lack of therapeutic options and their rapid emergence globally over the last decade (Center of Disease Control, 2013). Tn4401 is capable of mobilization at a high frequency (Cuzon et al, 2011), and is almost always located on a plasmid which increases the likelihood of spread of blaKPC. After the introduction of KPC-Enterobacteriales (KPCE) to our institution in 2007, and in the context of on-going transmission, the screening of high-risk patients for asymptomatic carriage of KPCE was implemented in 2009 to try and reduce colonization and infection rates (Mathers et al, 2014). In 2013, there was recognition that wastewater premise plumbing was colonized with KPCE and we began environmental surveillance and mitigation strategies (Mathers et al, 2018). Hospital wastewater premise plumbing is increasingly recognized as a reservoir for CPE (Decraene et al, 2018; Kizny Gordon, 2014), and an ideal niche for the horizontal gene transfer of antimicrobial resistance (AMR) genes (Conlan et al, 2014)

Methods

Results

Conclusion