High Incidence of Escherichia coli Strains Coharboring mcr-1 and bla _NDM from Chickens

Abstract

This study investigated the characteristics of Escherichia coli isolates carrying mcr-1-bla NDM from a chicken farm in China. Of the 78 E. coli isolates, 21 clonally unrelated isolates carried mcr-1-bla NDM . Diverse IncI2 plasmids disseminated mcr-1, while the dissemination of bla NDM was mediated by diverse IncB/O plasmids. More striking was the colocalization of resistance genes mcr-1 and bla in an IncHI2/ST3 plasmid, which might pose a great challenge for public health.KEYWORDS high incidence, mcr-1, bla NDM , colocalization, Escherichia coli C arbapenems have been reliable and potent agents against Gram-negative bacteria. The rapid increase of carbapenem-resistant Enterobacteriaceae poses a great threat to public health and has prompted the reconsideration of colistin as a last-resort therapeutic option (1). Recently, a plasmid-borne colistin resistance gene (mcr-1) was identified in Escherichia coli and Klebsiella pneumoniae strains from animals and humans in China (2). This finding foreshadowed the inevitable dissemination of colistin resistance worldwide and was confirmed by the presence of mcr-1 in other countries (3-6).The mcr-1 gene is often associated with the extended-spectrum ␤-lactamase gene and has been found with bla CTX-M in the same plasmid (4,7,8). The mcr-1 gene has also emerged in carbapenem-resistant isolates (4, 9, 10), and the cotransfer of mcr-1 and carbapenem resistance genes is obviously of great clinical concern. Recently, mcr-1 was even found with bla NDM in the same IncX3-X4 hybrid plasmid in E. coli from pets in China (11). However, only a few isolates resistant to both carbapenem and colistin were characterized in those previous studies.Food-producing animals, especially chickens, serve as resistance gene "reservoirs," so it is crucial to identify the origins of multidrug-resistant plasmids in these animals. In this study, we investigated the genetically diverse E. coli isolates carrying mcr-1 and bla NDM from a chicken farm and characterized the plasmids harboring mcr-1 or bla NDM .Seventy-eight E. coli isolates were collected from diseased chickens in four separate barns on a large chicken farm (100,000 animals) in Shandong Province, China in October 2015. Feces from chickens that showed signs of diarrhea were randomly collected and streaked onto MacConkey agar. After incubating at 37°C for 20 h, one colony with typical E. coli morphology was selected from each chicken sample. Although detailed information on antibiotic usage was not available, ceftiofur and colistin were often used for prophylaxis and treatment of bacterial infections on this farm.Susceptibilities to 18 antimicrobials were determined for these 78 isolates by the agar dilution method using the recommended breakpoints (12, 13). The colistin breakpoint (Ն2 g/ml) was used according to recommendations by the European Committee for Antimicrobial Susceptibility Testing.

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

“…Different antibiotics usage may lead to various isolates selection. No resistant strains in this study co-harbored mcr-1 and bla NDM−1 gene, while in other studies from China, such strains were seen (Zheng et al, 2016;Liu et al, 2017b;Wang R. et al, 2018). For instances, in patients, different antibiotics treatment were adopted according to different illness and severity.…”

“…For livestock and poultry, antibiotics usage may also varied with breeding scales and farms. In addition to mcr-1 and bla NDM−1 gene, other genotype combination were also reported from China (Kong et al, 2017;Liu et al, 2017b;Chavda et al, 2018;Wang R. et al, 2018). The mcr and bla NDM genes co-harbored isolates from China are often E.…”

“…The rapid horizontal spread of drug-resistant genes by plasmids is one of the reasons for the increasing number of multidrug resistant bacteria, however, the transfer range of bacteria species is unknown. Studies have confirmed that many countries and regions have isolated Gram-negative bacteria with mcr-1 gene (Fernandes et al, 2016;Hadjadj et al, 2017;Liu et al, 2017a), the bla NDM−1 gene (Wang et al, 2014;Michael et al, 2015;Zenati et al, 2016;Abderrahim et al, 2017;Madec et al, 2017;Riazzo et al, 2017;Yu et al, 2017), or both (Zheng et al, 2016;Liu et al, 2017b;Wang R. et al, 2018), from humans, the environment and animals. Whether isolates from antibiotics-free and depopulated areas, wildlife, carried mcr or bla NDM genes is undiscovered.…”

Resistome Profiles, Plasmid Typing, and Whole-Genome Phylogenetic Tree Analyses of BlaNDM-9 and Mcr-1 Co-Harboring Escherichia coli ST617 from a Patient without a History of Farm Exposure in Korea

“…The first bla NDM-9 and mcr-1 co-harboring E. coli isolate belonged to a ST167 strain was followed by ST10 complexes, ST101, ST156, and ST297 [3,4]. The primary source was chicken meat.…”

“…Under the selective pressure of colistin, the first bla NDM-9 and mcr-1 co-harboring E. coli ST167 strain was identified from a retail chicken in 2016 [3]. Subsequent thereto, E. coli strains co-harboring bla NDM-9 and mcr-1 were reported from a chicken farm in China [4]. Since then, there have been concerns over the spread of this strain to humans.…”