Various Sequence Types of Escherichia coli Isolates Coharboring bla _NDM-5 and mcr-1 Genes from a Commercial Swine Farm in China

Abstract

Sixteen different sequence types (STs) of Escherichia coli isolates from a commercial swine farm in China were confirmed to coharbor the carbapenem resistance gene bla and the colistin resistance gene mcr-1. Whole-genome sequencing revealed that bla NDM-5 and mcr-1 were located on a 46-kb IncX3 plasmid and a 32-kb IncX4 plasmid, respectively. The two plasmids can transfer together with a low fitness cost, which might explain the presence of various STs of E. coli coharboring bla NDM-5 and mcr-1.KEYWORDS Escherichia coli, carbapenems, bla NDM-5 , colistin, mcr-1, fitness cost C arbapenemase-producing Enterobacteriaceae has become a major public health threat around the world (1). The recently identified carbapenemase New Delhi metallo-␤-lactamase confers resistance to all ␤-lactam antimicrobials except monobactam (2). The NDM-5-encoding gene bla NDM-5 was first identified in an Escherichia coli strain recovered from a patient in the United Kingdom in 2011 (3). Since then, bla was identified in many countries, such as Algeria (4-6), the United States (7), Australia (8), China (9-12), Denmark (13), Japan (14), India (15), and the United Kingdom (3). The widespread occurrence of NDM-5 in recent years should arouse our attention. Colistin is a critically important medication for humans in the treatment of carbapenemaseproducing Enterobacteriaceae, and it has been widely used in veterinary medicine in China (16,17). The first plasmid-mediated colistin resistance gene, mcr-1, was reported in E. coli in 2015 (18). In a short period, colistin-resistant E. coli carrying the mcr-1 gene were reported worldwide (19,20). Recently, mcr-1 was reported to coexist with bla NDM (21-23) and bla CTX-M (24), which brought great challenges for the treatment of bacterial infection. In the present study, we are the first to report the presence of isolates of various sequence types of E. coli coharboring bla NDM-5 and mcr-1 genes from a commercial pig farm in China.A total of 105 anal swabs samples from swine were collected from a commercial pig farm on 1 October 2015 in Sichuan province. E. coli strains were selected by eosinmethylene blue agar, and only 1 isolate was picked up from each sample. All 105 isolates were identified by BD Phoenix 100 diagnostic systems (Sparks, MD). Sixty-four strains were nonsusceptible to imipenem and polymyxin B, identified by the agar dilution method according to Clinical and Laboratory Standards Institute guidelines (25). Isolates were divided into 16 different clones by pulsed-field gel electrophoresis after XbaI digestion according to the standard PulseNet conditions (26) (Fig. 1). Phy-

Retrospective Screening and Analysis of mcr-1 and blaNDM in Gram-Negative Bacteria in China, 2010–2019

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Bacteria from Animals as a Pool of Antimicrobial Resistance Genes

“…Based on Delgado-Blas et al [194], Di Pilato et al [195], Jeannot et al [168], Kong et al [196], Liu et al [192] and Mediavilla et al [197]. A, animal origin; E, environmental origin; F, food origin; H, human origin; W, wildlife origin.…”

Antimicrobial Resistance on Farms: A Review Including Biosecurity and the Potential Role of Disinfectants in Resistance Selection

“…Resistance to this class of critically important human drugs has been detected among Enterobacteriaceae on pig farms in Germany, the United States, and China, plus in farmed and wild birds (Fischer et al., ; Köck et al., ; Kong et al., ; Mollenkopf et al., ; Roschanski et al., ). Carbapenems have never been licensed for veterinary use and resistance is a growing problem in human hospital and community medicine.…”