Avian-source mcr-1-positive Escherichia coli is phylogenetically diverse and shares virulence characteristics with E. coli causing human extra-intestinal infections

Phenotypic and genotypic characterization of Escherichia coli isolated from the chicken liver in relation to slaughterhouse conditions

Avian pathogenic Escherichia coli (APEC) has been identified as a sub-group of extraintestinal pathogenic E. coli (ExPEC). Recent studies indicate APEC as a potential foodborne zoonotic pathogen and a source or reservoir of human extraintestinal infections. The slaughtering and processing of poultry in low-income countries such as Jordan occurs in two distinct ways: in informal facilities known as Natafat and in formal slaughterhouses. This study compared E. coli phenotypes and genotypes according to slaughtering conditions (formal slaughterhouses vs. informal slaughter facilities). Therefore, liver samples (n = 242) were collected from formal (n = 121) and informal slaughter facilities (n = 121). Results revealed a high prevalence (94.2%) of E. coli among all isolates, with 59 (17 formal and 42 informal) isolates considered avian pathogenic E. coli (APEC) based on the virulence-associated genes. The prevalence of resistance among isolates was relatively high, reaching up to 99% against penicillin and 97% against nalidixic acid. However, the prevalence of resistance was the lowest (1.3%) against both meropenem and imipenem. Based on the MIC test findings, colistin resistance was 46.9% (107/228). The mcr -1 gene prevalence was 51.4% (55/107), of which 17.1 % were from formal plants (6/36) and 68.1% from informal facilities (49/72). Interestingly, only one isolate (0.9%) expressed mcr-10. Escherichia coli O157:H7 and associated virulence genes were found more in informal (n = 15 genes) than in formal slaughterhouses (n = 8). Phylogroups B1, C, and A were the most frequent in 228 E. coli isolates, while G, B2, and clade were the least frequent. In conclusion, these findings highlight the importance of implementing biosecurity measures in slaughterhouses to reduce antibiotic-resistant E. coli spread. Furthermore, this study provides valuable insights into the effects of wet market (Natafat) slaughter conditions on increasing bacterial resistance and virulence.

Emergence and Genomic Features of a mcr-1 Escherichia coli from Duck in Hungary

Plasmids carrying high-risk resistance mechanisms in pathogenic E. coli have gained particular attention in veterinary medicine, especially since the discovery of the colistin resistance gene, mcr-1. Here, we provide the first evidence of its emergence and describe the complete mcr-1 plasmid sequence of a multi-resistant avian pathogenic E. coli (APEC) strain from waterfowl in Hungary. Whole-genome sequencing analysis and core-genome MLST were performed to characterize the genome structure of the mcr-1 plasmid and to reveal the phylogenetic relation between the Hungarian duck strain Ec45-2020 and the internationally circulating mcr-1-positive E. coli strains from poultry and humans. Results showed that plasmid pEc45-2020-33kb displayed a high level of genome identity with mcr-1 plasmids of IncX4 type widespread among human, animal and food reservoirs of enteric bacteria of public health. The mcr-1-positive E. coli strain Ec45-2020 belongs to the ST162 genotype, considered as one of the globally disseminated zoonotic genotypes of MDR E. coli. In accordance with international findings, our results underline the importance of continuous surveillance of enteric bacteria with high-risk antimicrobial resistance genotypes, including neglected animals, such as waterfowls, as possible reservoirs for the colistin resistance gene mcr-1.

Complete genomic analysis of ST117 lineage extraintestinal pathogenic Escherichia coli (ExPEC) to reveal multiple genetic determinants to drive its global transmission: ST117 E. coli as an emerging multidrug-resistant foodborne ExPEC with zoonotic potential

Avian pathogenic Escherichia coli (APEC) is recognized as a primary source of foodborne extraintestinal pathogenic E. coli (ExPEC), which poses a significant risk of extraintestinal infections in humans. The potential of human infection with ST117 lineage APEC/ExPEC from poultry is particularly concerning. However, relatively few whole-genome studies have focused on ST117 as an emerging ExPEC lineage. In this study, the complete genomes of 11 avian ST117 isolates and the draft genomes of 20 ST117 isolates in China were sequenced to reveal the genomic islands and large plasmid composition of ST117 APEC. With reference to the extensive E. coli genomes available in public databases, large-scale comprehensive genomic analysis of the ST117 lineage APEC/ExPEC was performed to reveal the features of the ST117 pan-genome and population. The high variability of the accessory genome emphasized the diversity and dynamic traits of the ST117 pan-genome. ST117 isolates recovered from different hosts and geographic sources were randomly located on a phylogeny tree, suggesting that ST117 E. coli lacked host specificity. A time-scaled phylogeny tree showed that ST117 was a recent E. coli lineage with a relatively short evolutionary period. Further characterization of a wide diversity of ExPEC-related virulence genes, pathogenicity islands (PAIs), and resistance genes of the ST117 pan-genome provided insights into the virulence and resistance of ST117 APEC/ExPEC. The results suggested zoonotic potential of ST117 APEC/ExPEC between birds and humans. Moreover, genomic analysis showed that a pool of diverse plasmids drove the virulence and multidrug resistance of ST117 APEC/ExPEC. Several types of large plasmids were scattered across the ST117 isolates, but there was no strong plasmid-clade adaptation. Combined with the pan-genome analysis, a double polymerase chain reaction (PCR) method was designed for rapid and cost-effective detection of ST117 isolates from various avian and human APEC/ExPEC isolates. Overall, this study addressed a gap in current knowledge about the ST117 APEC/ExPEC genome, with significant implications to understand the success and spread of ST117 APEC/ExPEC.

Reductions in bacterial viability stimulate the production of Extra-intestinal Pathogenic Escherichia coli (ExPEC) cytoplasm-carrying Extracellular Vesicles (EVs)

Extra-intestinal Pathogenic Escherichia coli (ExPEC) is defined as an extra-intestinal foodborne pathogen, and several dominant sequence types (STs) ExPEC isolates are highly virulent, with zoonotic potential. Bacteria extracellular vesicles (EVs) carry specific subsets of molecular cargo, which affect various biological processes in bacteria and host. The mechanisms of EVs formation in ExPEC remains to be elucidated. Here, the purified EVs of ExPEC strains of different STs were isolated with ultracentrifugation processes. A comparative analysis of the strain proteomes showed that cytoplasmic proteins accounted for a relatively high proportion of the proteins among ExPEC EVs. The proportion of cytoplasm-carrying vesicles in ExPEC EVs was calculated with a simple green fluorescent protein (GFP) expression method. The RecA/LexA-dependent SOS response is a critical mediator of generation of cytoplasm-carrying EVs. The SOS response activates the expression of prophage-associated endolysins, Epel1, Epel2.1, and Epel2.2, which triggered cell lysis, increasing the production of ExPEC cytoplasm-carrying EVs. The repressor LexA controlled directly the expression of these endolysins by binding to the SOS boxes in the endolysin promoter regions. Reducing bacterial viability stimulated the production of ExPEC EVs, especially cytoplasm-carrying EVs. The imbalance in cell division caused by exposure to H₂O₂, the deletion of ftsK genes, or t⁶A synthesis defects activated the RecA/LexA-dependent SOS response, inducing the expression of endolysins, and thus increasing the proportion of cytoplasm-carrying EVs in the total ExPEC EVs. Antibiotics, which decreased bacterial viability, also increase the production of ExPEC cytoplasm-carrying EVs through the SOS response. Changes in the proportion of cytoplasm-carrying EVs affected the total DNA content of ExPEC EVs. When macrophages are exposed to a higher proportion of cytoplasm-carrying vesicles, ExPEC EVs were more cytotoxic to macrophages, accompanied with more-severe mitochondrial disruption and a higher level of induced intrinsic apoptosis. In summary, we offered comprehensive insight into the proteome analysis of ExPEC EVs. This study demonstrated the novel formation mechanisms of E. coli cytoplasm-carrying EVs.

Bacteria can release extracellular vesicles (EVs) into the extracellular environment. Bacterial EVs are primarily composed of protein, DNA, RNA, lipopolysaccharide (LPS), and diverse metabolite molecules. The molecular cargoes of EVs are critical for the interaction between microbes and their hosts, and affected various host biological processes. However, the mechanisms underlying the biogenesis of bacterial EVs had not been fully clarified in extra-intestinal pathogenic Escherichia coli (ExPEC). In this study, we demonstrated ExPEC EVs contained at least three types of vesicles, including outer membrane vesicles (OMVs), outer-inner membrane vesicles (OIMVs), and explosive outer membrane vesicles (EOMVs). Our results systematically identified important factors affecting the production of ExPEC cytoplasm-carrying EVs, especially EOMVs. A reduction in bacterial viability activated the RecA/LexA-dependent SOS response, inducing the expression of endolysins, which increased the production of ExPEC cytoplasm-carrying EVs. This increase in the proportion of cytoplasm-carrying EVs increased the cytotoxicity of EVs. It was noteworthy that antibiotics increased the production of ExPEC EVs, especially the numbers of cytoplasm-carrying EVs, which in turn increased EV cytotoxicity, suggesting that the treatment of infections of multidrug-resistant strains infection with antibiotics might cause greater host damage. Our study should improve the prevention and treatment of ExPEC infections.

High diversity of pathogenic Escherichia coli clones carrying mcr-1 among gulls underlines the need for strategies at the environment-livestock-human interface

The expansion of mcr-carrying bacteria is a well-recognized public health problem. Measures to contain mcr spread have mainly been focused on the food-animal production sector. Nevertheless, the spread of MCR-producers at the environmental interface particularly driven by the increasing population of gulls in coastal cities has been less explored. Occurrence of mcr-carrying Escherichia coli in gull's colonies faeces on a Portuguese beach was screened over 7-months. Cultural, molecular, and genomic approaches were used to characterize their diversity, mcr plasmids and adaptive features. Multidrug-resistant mcr-1-carrying E. coli were detected for three consecutive months. Over time, multiple strains were recovered, including zoonotic-related pathogenic E. coli clones (e.g., B2-ST131-H22, A-ST10, and B1-ST162). Diverse mcr-1.1 genetic environments were mainly associated with ST2/ST4-HI2 (ST10, ST131, ST162, ST354 and ST4204) but also IncI2 (ST12990) plasmids or in the chromosome (ST656). Whole-genome sequencing revealed enrichment of these strains on antibiotic resistance, virulence, and metal tolerance genes. Our results underscore gulls as important spreaders of high priority bacteria and genes that may affect the environment, food-animals and/or humans, potentially undermining One-Health strategies to reduce colistin resistance. This article is protected by copyright. All rights reserved.

Worldwide Prevalence of mcr-mediated Colistin-Resistance Escherichia coli in Isolates of Clinical Samples, Healthy Humans, and Livestock-A Systematic Review and Meta-Analysis

Background: Antimicrobial resistance is a serious public-health problem throughout the world. Escherichia coli, the most common Gram-negative microorganism, has developed different resistance mechanisms, making treating infections difficult. Colistin is considered a last-resort drug in the treatment of infections caused by E. coli. Plasmid-mediated mobile-colistin-resistant (mcr) genes in E. coli, now disseminated globally, are considered a major public-health threat. Humans, chickens, and pigs are the main reservoirs for E. coli and the sources of antibiotic resistance. Hence, an up-to-date and precise estimate of the global prevalence of mcr resistance genes in these reservoirs is necessary to understand more precisely the worldwide spread and to more effectively implement control and prevention strategies. Methodology: Publications were identified in the PubMed database on the basis of the PRISMA guidelines. English full-text articles were selected from December 2014 to March 2021. Descriptive statistics and a meta-analysis were performed in Excel and R software, respectively. Colistin resistance was defined as the molecular-genetic detection of the mcr genes. The crude and estimated prevalence were calculated for each host and continent. The studies were divided into two groups; community-based when they involved isolates from healthy humans, chickens, or pigs, and clinical studies when they involved only hospital, outpatient, or laboratory isolates. Results: A total of 1278 studies were identified and 218 were included in this systematic review and meta-analysis, divided into community studies (159 studies) and clinical studies (59 studies). The general prevalence of mcr-mediated colistin-resistant E. coli (mcrMCRE) was 6.51% (n = 11,583/177,720), reported in 54 countries and on five continents; Asia with 119 studies followed by Europe with 61 studies registered the most articles. Asia reported the major diversity of mcr-variants (eight of nine, except mcr-2). Worldwide, chickens and pigs proved to be the principal reservoir of mcr with an estimated prevalence of 15.8% and 14.9%, respectively. Healthy humans and clinical isolates showed a lower prevalence with 7.4% and 4.2% respectively. Conclusions: In this systematic review and meta-analysis, the worldwide prevalence of mcr in E. coli isolated from healthy humans, chickens, and pigs was investigated. A wide prevalence and distribution of mcr genes was demonstrated on all continents in E. coli isolates from the selected reservoirs. Understanding the epidemiology and occurrence in the reservoirs of mcr in E. coli on different continents of the world facilitates tracing how mcr genes are transmitted and determining the infection risks for humans. This knowledge can be used to reduce the incidence of zoonotic transmission by implementing the appropriate control programs.

Comparison of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Isolates From Rooks (Corvus frugilegus) and Contemporary Human-Derived Strains: A One Health Perspective

During winter, a large number of rooks gather and defecate at the park of a university clinic. We investigated the prevalence of extended-spectrum beta-lactamase (ESBL)–producing Escherichia coli in these birds and compared recovered isolates with contemporary human isolates. In 2016, fecal samples were collected from 112 trap-captured rooks and investigated for presence of ESBL producers using eosin methylene blue agar supplemented by 2 mg/L cefotaxime; 2,455 contemporary human fecal samples of patients of the clinics sent for routine culturing were tested similarly. In addition, 42 ESBL-producing E. coli isolates collected during the same period from inpatients were also studied. ESBL genes were sought for by PCR and were characterized by sequencing; E. coli ST131 clones were identified. Epidemiological relatedness was determined by pulsed-field gel electrophoresis and confirmed using whole genome sequencing in selected cases. Thirty-seven (33%) of sampled rooks and 42 (1.7%) of human stools yielded ESBL-producing E coli. Dominant genes were blaCTX–M–55 and blaCTX–M–27 in corvid, blaCTX–M–15 and blaCTX–M–27 in human isolates. ST162 was common among rooks. Two rook-derived E. coli belonged to ST131 C1-M27, which was also predominant (10/42) among human fecal and (15/42) human clinical isolates. Another potential link between rooks and humans was a single ST744 rook isolate grouped with one human fecal and three clinical isolates. Despite possible contact, genotypes shared between rooks and humans were rare. Thus, rooks are important as long-distance vectors and reservoirs of ESBL-producing E. coli rather than direct sources of infections to humans in our setting.

Antibiotic resistance and phylogenetic profiling of Escherichia coli from dairy farm soils; organic versus conventional systems

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First known comparison of antimicrobial resistance traits in E. coli strains from new zealand farms practicing organic and conventional husbandry.

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Potential extended spectrum β-lactamase producing strains isolated from dairy farm environments.

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Organic dairy farms tended to harbour fewer resistant isolates than those recovered from conventionally farmed counterparts.

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Evidence for anthroponotic transmission of resistant strains of human origin to farm environments.

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Implications for the spread of antimicrobial resistance traits from farm environments discussed.

The prevalence and spread of antimicrobial resistance (AMR) as a result of the persistent use and/or abuse of antimicrobials is a key health problem for health authorities and governments worldwide. A study of contrasting farming systems such as organic versus conventional dairy farming may help to authenticate some factors that may contribute to the prevalence and spread of AMR in their soils. A case study was conducted in organic and conventional dairy farms in the South Canterbury region of New Zealand.

A total of 814 dairy farm soil E. coli (DfSEC) isolates recovered over two years were studied. Isolates were recovered from each of two farms practicing organic, and another two practicing conventional husbandries. The E. coli isolates were examined for their antimicrobial resistance (AMR) against cefoxitin, cefpodoxime, chloramphenicol, ciprofloxacin, gentamicin, meropenem, nalidixic acid, and tetracycline. Phylogenetic relationships were assessed using an established multiplex PCR method. The AMR results indicated 3.7% of the DfSEC isolates were resistant to at least one of the eight selected antimicrobials. Of the resistant isolates, DfSEC from the organic dairy farms showed a lower prevalence of resistance to the antimicrobials tested, compared to their counterparts from the conventional farms. Phylogenetic analysis placed the majority (73.7%) of isolates recovered in group B1, itself dominated by isolates of bovine origin. The tendency for higher rates of resistance among strains from conventional farming may be important for future decision-making around farming practices Current husbandry practices may contribute to the prevalence and spread of AMR in the industry.

Updates on the global dissemination of colistin-resistant Escherichia coli: An emerging threat to public health

Colistin drug resistance is an emerging public health threat worldwide. The adaptability, existence and spread of colistin drug resistance in multiple reservoirs and ecological environmental settings is significantly increasing the rate of occurrence of multidrug resistant (MDR) bacteria such as Escherichia coli (E. coli). Here, we summarized the reports regarding molecular and biological characterization of mobile colistin resistance gene (mcr)-positive E. coli (MCRPEC), originating from diverse reservoirs, including but not limited to humans, environment, waste water treatment plants, wild, pets, and food producing animals. The MCRPEC revealed the abundance of clinically important resistance genes, which are responsible for MDR profile. A number of plasmid replicon types such as IncI2, IncX4, IncP, IncX, and IncFII with a predominance of IncI2 were facilitating the spread of colistin resistance. This study concludes the distribution of multiple sequence types of E. coli carrying mcr gene variants, which are possible threat to "One Health" perspective. In addition, we have briefly explained the newly known mechanisms of colistin resistance i.e. plasmid-encoded resistance determinant as well as presented the chromosomally-encoded resistance mechanisms. The transposition of ISApl1 into the chromosome and existence of intact Tn6330 are important for transmission and stability for mcr gene. Further, genetic environment of co-localized mcr gene with carbapenem-resistance or extended-spectrum β-lactamases genes has also been elaborated, which is limiting human beings to choose last resort antibiotics. Finally, environmental health and safety control measures along with spread mechanisms of mcr genes are discussed to avoid further propagation and environmental hazards of colistin resistance.

The role of potentiating mutations in the evolution of pandemic Escherichia coli clones

The Escherichia coli species exhibits a vast array of variable lifestyles, including environmental, commensal, and pathogenic organisms. Many of these E. coli contribute significantly to the global threat of antimicrobial resistance (AMR). Multidrug-resistant (MDR) clones of E. coli have arisen multiple times over varying timescales. The repeated emergence of successful pandemic clones, including the notorious ST131 lineage, highlights a desperate need to further study the evolutionary processes underlying their emergence and success. Here, we review the evolutionary emergence of E. coli ST131 pandemic clones and draw parallels between their evolutionary trajectories and those of other lineages. From colonization and expansion to the acquisition of multidrug resistance plasmids, potentiating mutations are present at each stage, leading to a proposed sequence of events that may result in the formation of an antimicrobial-resistant pandemic clone.

Emergence of Plasmid-Mediated Resistance Genes tet(X) and mcr-1 in Escherichia coli Clinical Isolates from Pakistan

The emergence of tet(X) represents a significant threat to human health. In this study, we aimed to investigate the genomic characterizations of tet(X)-positive clinical Escherichia coli isolates and provide genomic insight into the dissemination of antibiotic-resistant bacteria in clinical settings. Four tet(X)-positive E. coli isolates, PK5074, PK5086, PK5095, and PK5097, from 100 human clinical isolates were identified by PCR and were resistant to tigecycline. tet(X) genes were in IncFII plasmids in 4 E. coli isolates. Worryingly, PK5074 also carried an mcr-1-bearing IncHI2 plasmid. Notably, a relatively high cotransfer frequency of tet(X) and mcr-1 in PK5074 was found. PK5086, PK5095, and PK5097 were categorized into sequence type 410 (ST410) and indicated clonal dissemination of tet(X)-positive strains in hospitals, but tet(X)-bearing plasmids in PK5086, PK5095, and PK5097 were nontransferable. We present the first report of clinical E. coli isolates harboring tet(X) in South Asia. Our results support the implication of humans as a potential reservoir for tet(X)-harboring E. coli. We provide insight into the dissemination of tet(X) and mcr-1 in a clinical setting and highlight the current transmission of both critical resistance genes globally.

IMPORTANCE Global transmission of plasmid-mediated tigecycline resistance gene tet(X)-bearing Escherichia coli strains incurs a public health concern. However, the research focusing on the prevalence of tet(X)-positive isolates in clinical specimens is still rare, and to our knowledge, there is no such report from South Asia. Here, we characterized four E. coli clinical isolates harboring tet(X) of human origin in Pakistan and demonstrated clonal dissemination of tet(X)-positive isolates in hospitals. We report the emergence of an mcr-1-bearing IncHI2 plasmid together with a tet(X)-positive IncFII plasmid in one clinical isolate. Cotransfer of tet(X)- and mcr-1-carrying plasmids is worrying and warrants further investigations.

From farm to fork: Colistin voluntary withdrawal in Portuguese farms reflected in decreasing occurrence of mcr-1-carrying Enterobacteriaceae from chicken meat

Expansion of mcr-carrying Enterobacteriaceae (MCR-E) is a well-recognized problem affecting animals, humans and the environment. Ongoing global control actions involve colistin restrictions among food-animal production, but their impact on poultry-derived products is largely unknown, justifying comprehensive farm-to-fork studies. Occurrence of MCR-E among 53 chicken-meat batches supplied from 29 Portuguese farms shortly after colistin withdrawal was evaluated. Strains (FT-IR/MLST/WGS), mcr plasmids and their adaptive features were characterized by cultural, molecular and genomic approaches. We found high rates of chicken-meat batches (80%-100% - 4 months; 12% - the last month) with multiple MDR + mcr-1-carrying Escherichia coli (Ec-including ST117 and ST648-Cplx) and Klebsiella pneumoniae (Kp-ST147-O5:K35) clones, some of them persisting over time. The mcr-1 was located in the chromosome (Ec-ST297/16-farms) or dispersed IncX4 (Ec-ST602/ST6469/5-farms), IncHI2-ST2/ST4 (Ec-ST533/ST6469/5 farms and Kp-ST147/6-farms) or IncI2 (Ec-ST117/1-farm) plasmids. WGS revealed high load and diversity in virulence, antibiotic resistance and metal tolerance genes. This study supports colistin withdrawal potential efficacy in poultry production and highlights both poultry-production chain as a source of mcr-1 and the risk of foodborne transmission to poultry-meat consumers. Finally, in the antibiotic reduction/replacement context, other potential co-selective pressures (e.g., metals-Cu as feed additives) need to be further understood to guide concerted, effective and durable actions under 'One Health' perspective.

Avian Pathogenic Escherichia coli (APEC): An Overview of Virulence and Pathogenesis Factors, Zoonotic Potential, and Control Strategies

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in avian species, and recent reports have suggested APEC as a potential foodborne zoonotic pathogen. Herein, we discuss the virulence and pathogenesis factors of APEC, review the zoonotic potential, provide the current status of antibiotic resistance and progress in vaccine development, and summarize the alternative control measures being investigated. In addition to the known virulence factors, several other factors including quorum sensing system, secretion systems, two-component systems, transcriptional regulators, and genes associated with metabolism also contribute to APEC pathogenesis. The clear understanding of these factors will help in developing new effective treatments. The APEC isolates (particularly belonging to ST95 and ST131 or O1, O2, and O18) have genetic similarities and commonalities in virulence genes with human uropathogenic E. coli (UPEC) and neonatal meningitis E. coli (NMEC) and abilities to cause urinary tract infections and meningitis in humans. Therefore, the zoonotic potential of APEC cannot be undervalued. APEC resistance to almost all classes of antibiotics, including carbapenems, has been already reported. There is a need for an effective APEC vaccine that can provide protection against diverse APEC serotypes. Alternative therapies, especially the virulence inhibitors, can provide a novel solution with less likelihood of developing resistance.

Virulence Properties of mcr-1-Positive Escherichia coli Isolated from Retail Poultry Meat

The great plasticity and diversity of the Escherichia coli genome, together with the ubiquitous occurrence, make E. coli a bacterium of world-wide concern. Of particular interest are pathogenic strains and strains harboring antimicrobial resistance genes. Overlapping virulence-associated traits between avian-source E. coli and human extraintestinal pathogenic E. coli (ExPEC) suggest zoonotic potential and safety threat of poultry food products. We analyzed whole-genome sequencing (WGS) data of 46 mcr-1-positive E. coli strains isolated from retail raw meat purchased in the Czech Republic. The investigated strains were characterized by their phylogroup-B1 (43%), A (30%), D (11%), E (7%), F (4%), B2 (2%), C (2%), MLST type, and serotype. A total of 30 multilocus sequence types (STs), of which ST744 was the most common (11%), were identified, with O8 and O89 as the most prevalent serogroups. Using the VirulenceFinder tool, 3 to 26 virulence genes were detected in the examined strains and a total of 7 (15%) strains met the pathogenic criteria for ExPEC. Four strains were defined as UPEC (9%) and 18 (39%) E. coli strains could be classified as APEC. The WGS methods and available on-line tools for their evaluation enable a comprehensive approach to the diagnosis of virulent properties of E. coli strains and represent a suitable and comfortable platform for their detection. Our results show that poultry meat may serve as an important reservoir of strains carrying both virulence and antibiotic resistance genes for animal and human populations.

Role of Plasmids in the Ecology and Evolution of "High-Risk" Extraintestinal Pathogenic Escherichia coli Clones

Bacterial plasmids have been linked to virulence in Escherichia coli and Salmonella since their initial discovery. Though the plasmid repertoire of these bacterial species is extremely diverse, virulence-associated attributes tend to be limited to a small subset of plasmid types. This is particularly true for extraintestinal pathogenic E. coli, or ExPEC, where a handful of plasmids have been recognized to confer virulence- and fitness-associated traits. The purpose of this review is to highlight the biological and genomic attributes of ExPEC virulence-associated plasmids, with an emphasis on high-risk dominant ExPEC clones. Two specific plasmid types are highlighted to illustrate the independently evolved commonalities of these clones relative to plasmid content. Furthermore, the dissemination of these plasmids within and between bacterial species is examined. These examples demonstrate the evolution of high-risk clones toward common goals, and they show that rare transfer events can shape the ecological landscape of dominant clones within a pathotype.

First Report of an Escherichia coli Strain Carrying the Colistin Resistance Determinant mcr-1 from a Dog in South Korea

We studied the presence of the mobile colistin resistance gene mcr-1 in Escherichia coli isolates recovered from fecal and urine samples of companion animals, that were collected from South Korea in 2018 and 2019. The mcr-1 gene was detected in one colistin-resistant E. coli isolated from a diarrheic dog. The isolate exhibited additional resistance to multiple antimicrobials, including fluoroquinolones and third-generation cephalosporins. The mcr-1 carrying isolate belonged to ST160. The pulsed-field gel electrophoresis pattern of our strain differed from those ST160 E. coli strains previously identified from chickens in Korea. The mcr-1 gene was identified in the IncI2 plasmid. It was also transferred to E. coli J53 recipient strain, with a conjugation efficiency of 2.8 × 10-4. Average nucleotide identity analysis demonstrated that the mcr-1-carrying plasmid in this study was closely related to those from patients in Korea. To the best of our knowledge, this is the first report of mcr-1 carrying E. coli from a companion animal in South Korea. Our findings support One Health approach is necessary to prevent the dissemination of this high-risk gene.

Coexistence of blaKPC-2-IncN and mcr-1-IncX4 plasmids in a ST48 Escherichia coli strain in China

OBJECTIVES

The aim of this study was to explore the genomic content of a bla_KPC-2- and mcr-1-harbouring Escherichia coli strain and to clarify the molecular mechanism for the transmission of multidrug resistance.

METHODS

Antimicrobial susceptibility testing was conducted by the broth microdilution method to determine the resistance profile. Filter-mating conjugation assays were performed to confirm the plasmid transfer ability. Whole-genome sequence data were acquired by a combination of Illumina paired-end reads and Nanopore long-read sequencing.

RESULTS

Escherichia coli strain QE11-421 was an mcr-1-positive colistin-resistant isolate that co-harboured the bla_KPC-2 gene conferring carbapenem resistance. Genome sequence data confirmed QE11-421 as a sequence type 48 (ST48) E. coli that harboured five large conjugative plasmids encoding several multidrug resistance genes. The bla_KPC-2 gene was located on a Tn3-Tn4401 composite transposon, which is part of a 65-kb multidrug-resistant IncN plasmid. The mcr-1 gene was harboured on another 33-kb IncX4 plasmid that was more conserved and presented few antimicrobial resistance determinants. No copies of insertion sequence ISApl1 were found flanking the mcr-1 gene, decreasing the mobility of mcr-1 based on its original Tn6330 transposon.

CONCLUSIONS

Horizontal transfer of multidrug resistance plasmids or resistance-related transposon units was responsible for the emergence of this notorious superbug. The coexistence of bla_KPC-2-IncN and mcr-1-IncX4 plasmids in a ST48 E. coli strain in humans poses a great threat.