Plasmid-borne Colistin Resistance Research Articles

Outer membrane permeability of mcr-positive bacteria reveals potent synergy of colistin and macromolecular antibiotics against colistin-resistant Acinetobacter baumannii.

Colistin (CT) is the last-resort of antibiotic against multidrug-resistance (MDR) Acinetobacter baumannii (A. baumannii) infection. However, colistin resistance is increasingly reported in A. baumannii isolates partially due to the global emergence and dissemination of plasmid-borne mobile colistin resistance (mcr) gene and is a threat to human health. Thus, available treatment strategies urgently required in the fight against colistin-resistant A. baumannii. Here, we showed that mcr confers damaged outer membrane (OM) permeability in A. baumannii, which could compromise the viability of A. baumannii. Consistently, A. baumannii with colistin resistance exhibits increased susceptibility to macromolecular antibiotics such as rifampicin (RIF) and erythromycin (ERY). Moreover, the combination therapy of colistin and rifampicin demonstrates efficacy against colistin-resistant A. baumannii, regardless of the presence of mcr. Altogether, our data suggest that the synergy of colistin in combination with macromolecular hydrophobic antibiotics poses a promising therapeutic alternative for colistin-resistant A. baumannii.

Emergence of the mobile colistin resistance gene mcr-1 in a Leclercia adecarboxylata strain isolated from wastewater in Seoul

Colistin is considered the last resort for treating infections caused by multidrug-resistant bacteria. However, the spread of the plasmid-borne colistin-resistance gene mcr-1 has become a public health threat. In this study, we identified mcr-1-harboring Leclercia adecarboxylata strain (WWCOL-134) isolated from wastewater in Seoul. The strain had a colistin MIC value of 2 µg/ml and was resistant to cefotaxime, gentamicin, tetracycline, trimethoprim and sulfamethoxazole. The mcr-1 gene, along with an array of resistance genes, was located on a 236-kb plasmid (pCOL134-1), which contained the typical IncHI2 backbone of reported mcr-1-carrying plasmids, and was transferred to an Escherichia coli strain by conjugation. To the best of our knowledge, this is the first study to report the emergence of mcr-1-harboring Leclercia sp. isolate. Our findings demonstrate the ongoing spread of colistin resistance among Enterobacterales species, emphasizing the need for surveillance of antimicrobial resistance in wastewater environments.

First report of mobile colistin resistance gene mcr-1 in avian pathogenic Escherichia coli isolated from turkeys in the Gaza Strip, Palestine.

Colistin is used to treat avian pathogenic Escherichia coli (APEC), a microorganism that affects turkey meat production in the Gaza Strip and worldwide. However, the recent emergence of plasmid-borne mobile colistin resistance (mcr) genes in pathogenic E. coli strains is a serious antimicrobial resistance (AMR) challenge for both human and animal health. In December 2018, colistin was banned as a veterinary antimicrobial in the Gaza Strip. This study aimed to detect and track the prevalence of colistin-resistant APEC isolated from turkey flocks in the Gaza Strip. This study investigated 239 APEC isolates from turkey flocks in the Gaza Strip between October 2018 and December 2021 (at 6-month intervals). The colistin-resistant APEC strains were detected using the broth microdilution method. The mcr-1 gene was identified using a polymerase chain reaction. The overall colistin resistance among the isolated APECs was 32.2% during the study period. The average resistance in the first interval was 37.5%, which significantly decreased to 9.3% in the last interval. Among the 77 phenotypically resistant isolates, 32.4% were positive for mcr-1. The average abundance of mcr-1 in the first interval was 66.6%, which decreased to 25% in the last interval. To the best of our knowledge, this is the first study reporting the presence of the mcr-1 gene among the APEC isolates from turkeys in the Gaza Strip. Banned veterinary use of colistin significantly decreased the percentage of resistant APEC isolates from turkeys in Gaza Strip. Further studies are needed to investigate other colistin resistance genes and track the emergence of AMR.

Inhibiting fatty acid synthesis overcomes colistin resistance.

Treating multidrug-resistant infections has increasingly relied on last-resort antibiotics, including polymyxins, for example colistin. As polymyxins are given routinely, the prevalence of their resistance is on the rise and increases mortality rates of sepsis patients. The global dissemination of plasmid-borne colistin resistance, driven by the emergence of mcr-1, threatens to diminish the therapeutic utility of polymyxins from an already shrinking antibiotic arsenal. Restoring sensitivity to polymyxins using combination therapy with sensitizing drugs is a promising approach to reviving its clinical utility. Here we describe the ability of the biotin biosynthesis inhibitor, MAC13772, to synergize with colistin exclusively against colistin-resistant bacteria. MAC13772 indirectly disrupts fatty acid synthesis (FAS) and restores sensitivity to the last-resort antibiotic, colistin. Accordingly, we found that combinations of colistin and other FAS inhibitors, cerulenin, triclosan and Debio1452-NH3, had broad potential against both chromosomal and plasmid-mediated colistin resistance in chequerboard and lysis assays. Furthermore, combination therapy with colistin and the clinically relevant FabI inhibitor, Debio1452-NH3, showed efficacy against mcr-1 positive Klebsiella pneumoniae and colistin-resistant Escherichia coli systemic infections in mice. Using chemical genomics, lipidomics and transcriptomics, we explored the mechanism of the interaction. We propose that inhibiting FAS restores colistin sensitivity by depleting lipid synthesis, leading to changes in phospholipid composition. In all, this work reveals a surprising link between FAS and colistin resistance.

Exploring the epidemiology of mcr genes, genetic context and plasmids in Enterobacteriaceae originating from pigs and humans on farms in Thailand.

In veterinary medicine, colistin has been widely used as therapeutic and prophylactic agent, and for growth promotion. However, colistin has been re-introduced into treatment of human MDR bacterial infections. We assessed the characteristics and spread of plasmid-borne colistin resistance among healthy pigs, workers with animal-contact and their household members in Thailand. WGS and MIC data of 146 mcr-positive isolates from a cross-sectional One Health study were analysed. Long-read sequencing and conjugation were performed for selected isolates. mcr-carrying isolates were detected in 38% of pooled-pig samples and 16% of human faecal samples. Of 143 Escherichia coli and three Escherichia fergusonii, mcr-1, mcr-3, and mcr-9 variants were identified in 96 (65.8%), 61 (41.8%) and one (0.7%) isolate, respectively. Twelve E. coli co-harboured two mcr variants (mcr-1 and mcr-3). Clonal transmission was detected in five out of 164 farms. mcr-1 was mostly harboured by epidemic IncX4 and IncHI1 plasmids (89.9%). Conversely, mcr-3 was harboured by a range of different plasmids. Comparative plasmid studies suggested IncP and IncFII plasmids as possible endemic mcr-3 plasmids in Asian countries. Moreover, mcr-3 was associated with different mobile genetic elements including TnAs2, ISKpn40 and IS26/15DI. Detected genetic signatures (DRs) indicated recent mcr-3 transpositions, underlining the mobilizable nature of the mcr-3 cassette. The epidemiology of mcr and the possible evolution of successful plasmids and transposition modules should be carefully monitored. Of special concern is the growing number of different horizontal gene transferring pathways encompassing various transposable modules the mcr genes can be shared between bacteria.

First Detection of mcr-9 in a Multidrug-Resistant Escherichia coli of Animal Origin in Italy Is Not Related to Colistin Usage on a Pig Farm.

The emergence of colistin resistance raises growing concerns because of its use as a last-resort antimicrobial for the treatment of severe gram-negative bacterial infections in humans. Plasmid-borne mobile colistin resistance genes (mcr) are particularly worrisome due to their high propensity to spread. An mcr-9-positive Escherichia coli was isolated from a piglet in Italy, representing the first isolation of this gene from an E. coli of animal origin in the country. Whole genome sequencing (WGS) revealed that mcr-9 was borne by an IncHI2 plasmid carrying several other resistance genes. The strain was indeed phenotypically resistant to six different antimicrobial classes, including 3rd and 4th generation cephalosporins. Despite the presence of mcr-9, the isolate was susceptible to colistin, probably because of a genetic background unfavourable to mcr-9 expression. The lack of colistin resistance, coupled with the fact that the farm of origin had not used colistin in years, suggests that mcr-9 in such a multidrug-resistant strain can be maintained thanks to the co-selection of neighbouring resistance genes, following usage of different antimicrobials. Our findings highlight how a comprehensive approach, integrating phenotypical testing, targeted PCR, WGS-based techniques, and information on antimicrobial usage is crucial to shed light on antimicrobial resistance.

Plasmid-borne mobile colistin resistance (MCR-1) in healthy humans and poultry

Background and aim: The emergence of antimicrobial-resistant bacteria has become a menace to global public health and socio-economic development. Colistin is used as the last resort antibiotic in refractory infections. However, resistant isolates are reported frequently. The aim of this study was to find mcr genes in healthy people poultry farms in Sanandaj, west of Iran. Methods and materials: In this study, faecal samples were collected from two groups of humans and poultry. Colistin-containing screening media as well as colistin-EDTA-containing medium to screen plasmid-mediated colistin resistance. PCR for prevalent mcr genes was performed. Antimicrobial susceptibility testing was done for MCR-harboring isolates. Results: In this study, no colistin-resistant bacteria were isolated from poultry samples (0%) while two human E. coli isolates showed resistance to colistin (0.59%). Of which, one isolate was inhibited by EDTA and harboured the MCR-1 variant. The MIC for colistin was 16 mg/L. Conclusion: The results indicated the low prevalence of this gene in healthy individuals and the poultry industry. To the best of our knowledge, this is the first report of MCR in healthy individuals from Iran.

Complete Genome Sequence of an mcr-10-Carrying Enterobacter roggenkampii Strain Isolated from a Human Blood Culture.

The mcr-10 gene is a plasmid-borne colistin resistance gene. The complete genome sequence of an mcr-10-carrying Enterobacter roggenkampii clinical strain that had been isolated from a blood culture was obtained. The genome consists of a 4.95-Mbp chromosome and six plasmids, including a 195-kb plasmid harboring mcr-10 and two replicons, IncFIB(K) and IncFII(Yp).

MgrB Mutations and Altered Cell Permeability in Colistin Resistance in Klebsiella pneumoniae.

There has been a resurgence in the clinical use of polymyxin antibiotics such as colistin due to the limited treatment options for infections caused by carbapenem-resistant Enterobacterales (CRE). However, this last-resort antibiotic is currently confronted with challenges which include the emergence of chromosomal and plasmid-borne colistin resistance. Colistin resistance in Klebsiella pneumoniae is commonly caused by the mutations in the chromosomal gene mgrB. MgrB spans the inner membrane and negatively regulates PhoP phosphorylation, which is essential for bacterial outer membrane lipid biosynthesis. The present review intends to draw attention to the role of mgrB chromosomal mutations in membrane permeability in K. pneumoniae that confer colistin resistance. With growing concern regarding the global emergence of colistin resistance, deciphering physical changes of the resistant membrane mediated by mgrB inactivation may provide new insights for the discovery of novel antimicrobials that are highly effective at membrane penetration, in addition to finding out how this can help in alleviating the resistance situation.

Emergence of a novel hybrid mcr-1-bearing plasmid in an NDM-7-producing ST167 Escherichia coli strain of clinical origin.

Colistin is considered as an antibiotic of ‘last resort’ for the treatment of lethal infections caused by carbapenem-resistant Enterobacterales (CRE), dissemination of plasmid-borne colistin resistance gene mcr-1, particularly into CRE, resulting in the emergence of strains that approach pan-resistance. A wide variety of plasmid types have been reported for carrying mcr-1. Among which, large IncHI2-type plasmids were multidrug-resistant (MDR) plasmids harbored multiple resistance determinants in addition to mcr-1. Herein, we characterized a novel hybrid IncHI2-like mcr-1-bearing plasmid in an NDM-7-producing ST167 Escherichia coli strain EC15-50 of clinical origin. Antimicrobial susceptibility testing showed E. coli EC15-50 exhibited an extensively drug-resistant (XDR) profile that only susceptible to amikacin and tigecycline. S1-PFGE, Southern hybridization and Whole-genome Sequencing (WGS) analysis identified a 46,161 bp blaNDM-7-harboring IncX3 plasmid pEC50-NDM7 and a 350,179 bp mcr-1-bearing IncHI2/HI2A/N/FII/FIA plasmid pEC15-MCR-50 in E. coli EC15-50. Sequence detail analysis revealed the type IV coupling protein (T4CP) gene was absent on pEC15-MCR-50, explaining that pEC15-MCR-50 was a non-conjugative plasmid. Comparative genetic analysis indicated the hybrid plasmid pEC15-MCR-50 was probably originated from pXGE1mcr-like IncHI2/HI2A/N plasmid and pSJ_94-like IncFII/FIA plasmid, and generated as a result of a replicative transposition process mediated by IS26. Currently, the prevalent mcr-1-carrying IncHI2 plasmids were rarely reported to be fused with other plasmids. The identification of the novel hybrid plasmid pEC15-MCR-50 in this study highlighted the importance of close surveillance for the emergence and dissemination of such fusion MDR plasmids, particularly in NDM-producing Enterobacterales.

First report from supermarket chicken meat and genomic characterization of colistin resistance mediated by mcr-1.1 in ESBL-producing, multidrug-resistant Salmonella Minnesota

Plasmid-borne colistin resistance is considered one of the most complex public health concerns worldwide. Several studies reported the presence of the mcr-1.1 harboring Salmonella from the foodstuffs worldwide; still, there is a knowledge gap about the occurrence of these isolates in the Middle East. In this study, we report an mcr-1.1-mediated colistin resistance in two multidrug-resistant (MDR) S. Minnesota (denoted as Sal_2 and Sal_10), with both being also extended-spectrum β-lactamase (ESBL) producing. These isolates have been recovered from two independent samples out of 315 chilled chicken meat tested from retail supermarkets in the United Arab Emirates (UAE). Based on whole-genome sequencing (WGS) analysis, both isolates belonged to the same Sequence Type (ST) ST548. They shared the same genes encoding resistance to the following antimicrobials: polymyxin (mcr-1.1), phenicol (floR), quinolone (qnrB19), aminoglycoside (aac(6′)-Iaa), tetracycline (tet(A)), and sulfonamide (sul2). However, the isolates featured different patterns of β-lactamase resistance genes, which included blaCTX-M-55 (ESBL-β-lactamase) and blaCMY-2 (AmpC-β-lactamase) in the isolate Sal_2, and blaTEM-215 (ESBL-β-lactamase) in the isolate Sal_10. WGS analysis inferred that both S. Minnesota isolates in this study carry an IncX4 plasmid harboring the mcr-1.1 variant. To understand the possible origin of the two mcr-1.1 carrying S. Minnesota isolated from retail chicken meat in this study, we conducted a phylogenomic analysis using available genomes of S. enterica, which harbored mcr-1.1 gene (n = 240, from the Middle East and Asian countries) deposited in the NCBI database. We found that Sal_2 and Sal_10 independently clustered together with other isolates detected in China, mainly from the chicken origin and to a lesser extent from human clinical origin. The finding of mcr-producing colistin-resistant strains in retail chicken meat warrants a more comprehensive One Health investigations involving strains from animals, retail food chains, and human clinical isolates at the national level in the UAE.

Letter to the Editor: First Report of the Detection of the Plasmid-Borne Colistin Resistance Gene, mcr-1.26, in Multidrug-Resistant Escherichia coli Isolated from a Domesticated Pigeon.

Microbial Drug ResistanceVol. 28, No. 7 Veterinary MicrobiologyLetter to the Editor: First Report of the Detection of the Plasmid-Borne Colistin Resistance Gene, mcr-1.26, in Multidrug-Resistant Escherichia coli Isolated from a Domesticated PigeonIssmat I. Kassem, Ali Assi, Marwan Osman, David Mann, Shaoting Li, and Xiangyu DengIssmat I. KassemAddress correspondence to: Issmat I. Kassem, PhD, Food Science and Technology, Center for Food Safety, University of Georgia, 1109 Experiment Street, Griffin, GA 30223, USA E-mail Address: issmat.kassem@uga.eduFood Science and Technology, Center for Food Safety, University of Georgia, Athens, Georgia, USA.Search for more papers by this author, Ali AssiNutrition and Food Sciences, Faculty of Agricultural and Food Sciences, American University of Beirut (AUB), Beirut, Lebanon.Search for more papers by this author, Marwan OsmanDepartment of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.Search for more papers by this author, David MannFood Science and Technology, Center for Food Safety, University of Georgia, Athens, Georgia, USA.Search for more papers by this author, Shaoting LiFood Science and Technology, Center for Food Safety, University of Georgia, Athens, Georgia, USA.Search for more papers by this author, and Xiangyu DengFood Science and Technology, Center for Food Safety, University of Georgia, Athens, Georgia, USA.Search for more papers by this authorPublished Online:13 Jul 2022https://doi.org/10.1089/mdr.2021.0359AboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View articleFiguresReferencesRelatedDetailsCited byEditorial: Antimicrobial resistance and antimicrobial alternatives6 March 2023 | Frontiers in Medicine, Vol. 10 Volume 28Issue 7Jul 2022 InformationCopyright 2022, Mary Ann Liebert, Inc., publishersTo cite this article:Issmat I. Kassem, Ali Assi, Marwan Osman, David Mann, Shaoting Li, and Xiangyu Deng.Letter to the Editor: First Report of the Detection of the Plasmid-Borne Colistin Resistance Gene, mcr-1.26, in Multidrug-Resistant Escherichia coli Isolated from a Domesticated Pigeon.Microbial Drug Resistance.Jul 2022.821-823.http://doi.org/10.1089/mdr.2021.0359Published in Volume: 28 Issue 7: July 13, 2022Online Ahead of Print:May 30, 2022PDF download

Pharmacokinetics and Pharmacodynamics of Colistin Combined With Isopropoxy Benzene Guanidine Against mcr-1-Positive Salmonella in an Intestinal Infection Model.

Plasmid-borne colistin resistance mediated by mcr-1 is a growing problem, which poses a serious challenge to the clinical application of colistin for Gram-negative bacterial infections. Drug combination is one of the effective strategies to treat colistin-resistant bacteria. Here, we found a guanidine compound, namely, isopropoxy benzene guanidine (IBG), which boosted the efficacy of colistin against mcr-1-positive Salmonella. This study aimed to develop a pharmacokinetics/pharmacodynamics (PK/PD) model by combining colistin with IBG against mcr-1-positive Salmonella in an intestinal infection model. Antibiotic susceptibility testing, checkerboard assays and time-kill curves were used to investigate the antibacterial activity of the synergistic activity of the combination. PK studies of colistin in the intestine were determined through oral gavage of single dose of 2, 4, 8, and 16 mg/kg of body weight in broilers with intestinal infection. On the contrary, PD studies were conducted over 24 h based on a single dose ranging from 2 to 16 mg/kg. The inhibitory effect Imax model was used for PK/PD modeling. The combination of colistin and IBG showed significant synergistic activity. The AUC0−24h/MIC index was used to evaluate the relationship between PK and PD, and the correlation was >0.9085. The AUC0−24h /MIC targets in combination required to achieve the bacteriostatic action, 3-log10 kill, and 4-log10 kill of bacterial counts were 47.55, 865.87, and 1894.39, respectively. These results can facilitate the evaluation of the use of IBG as a potential colistin adjuvant in the treatment of intestinal diseases in broilers caused by colistin-resistant Salmonella.

Plasmid Mediated mcr-1.1 Colistin-Resistance in Clinical Extraintestinal Escherichia coli Strains Isolated in Poland.

Objectives: The growing incidence of multidrug-resistant (MDR) bacteria is an inexorable and fatal challenge in modern medicine. Colistin is a cationic polypeptide considered a “last-resort” antimicrobial for treating infections caused by MDR Gram-negative bacterial pathogens. Plasmid-borne mcr colistin resistance emerged recently, and could potentially lead to essentially untreatable infections, particularly in hospital and veterinary (livestock farming) settings. In this study, we sought to establish the molecular basis of colistin-resistance in six extraintestinal Escherichia coli strains.Methods: Molecular investigation of colistin-resistance was performed in six extraintestinal E. coli strains isolated from patients hospitalized in Medical University Hospital, Bialystok, Poland. Complete structures of bacterial chromosomes and plasmids were recovered with use of both short- and long-read sequencing technologies and Unicycler hybrid assembly. Moreover, an electrotransformation assay was performed in order to confirm IncX4 plasmid influence on colistin-resistance phenotype in clinical E. coli strains.Results: Here we report on the emergence of six mcr-1.1-producing extraintestinal E. coli isolates with a number of virulence factors. Mobile pEtN transferase-encoding gene, mcr-1.1, has been proved to be encoded within a type IV secretion system (T4SS)-containing 33.3 kbp IncX4 plasmid pMUB-MCR, next to the PAP2-like membrane-associated lipid phosphatase gene.Conclusion: IncX4 mcr-containing plasmids are reported as increasingly disseminated among E. coli isolates, making it an “epidemic” plasmid, responsible for (i) dissemination of colistin-resistance determinants between different E. coli clones, and (ii) circulation between environmental, industrial, and clinical settings. Great effort needs to be taken to avoid further dissemination of plasmid-mediated colistin resistance among clinically relevant Gram-negative bacterial pathogens.

Destination shapes antibiotic resistance gene acquisitions, abundance increases, and diversity changes in Dutch travelers

BackgroundAntimicrobial-resistant bacteria and their antimicrobial resistance (AMR) genes can spread by hitchhiking in human guts. International travel can exacerbate this public health threat when travelers acquire AMR genes endemic to their destinations and bring them back to their home countries. Prior studies have demonstrated travel-related acquisition of specific opportunistic pathogens and AMR genes, but the extent and magnitude of travel’s effects on the gut resistome remain largely unknown.MethodsUsing whole metagenomic shotgun sequencing, functional metagenomics, and Dirichlet multinomial mixture models, we investigated the abundance, diversity, function, resistome architecture, and context of AMR genes in the fecal microbiomes of 190 Dutch individuals, before and after travel to diverse international locations.ResultsTravel markedly increased the abundance and α-diversity of AMR genes in the travelers’ gut resistome, and we determined that 56 unique AMR genes showed significant acquisition following international travel. These acquisition events were biased towards AMR genes with efflux, inactivation, and target replacement resistance mechanisms. Travel-induced shaping of the gut resistome had distinct correlations with geographical destination, so individuals returning to The Netherlands from the same destination country were more likely to have similar resistome features. Finally, we identified and detailed specific acquisition events of high-risk, mobile genetic element-associated AMR genes including qnr fluoroquinolone resistance genes, blaCTX-M family extended-spectrum β-lactamases, and the plasmid-borne mcr-1 colistin resistance gene.ConclusionsOur results show that travel shapes the architecture of the human gut resistome and results in AMR gene acquisition against a variety of antimicrobial drug classes. These broad acquisitions highlight the putative risks that international travel poses to public health by gut resistome perturbation and the global spread of locally endemic AMR genes.

Prevalence and Antibiotic Resistance Characteristics of Extraintestinal Pathogenic Escherichia coli among Healthy Chickens from Farms and Live Poultry Markets in China.

Simple SummaryChicken meat has been proved to be a suspected source of extraintestinal pathogenic Escherichia coli (ExPEC), causing several diseases in humans, and bacteria in healthy chickens can contaminate chicken carcasses at the slaughter; however, reports about the prevalence and molecular characteristics of ExPEC in healthy chickens are still rare. In this study, among 926 E. coli isolates from healthy chickens in China, 22 (2.4%) were qualified as ExPEC and these ExPEC isolates were clonally unrelated. A total of six serogroups were identified in this study, with O78 being the most predominant type, and all the six serogroups had been frequently reported in human ExPEC isolates in many countries. All the 22 ExPEC isolates were multidrug-resistant and most isolates carried both blaCTX-M and fosA3 resistance genes. Notably, plasmid-borne colistin resistance gene mcr-1 was identified in six ExPEC isolates, among which two carried additional carbapenemase gene blaNDM, compromising both the efficacies of the two critically important drugs for humans, carbapenems and colistin. These results highlight that healthy chickens can serve as a potential reservoir for multidrug resistant ExPEC isolates, including mcr-1-containing ExPEC.Chicken products and chickens with colibacillosis are often reported to be a suspected source of extraintestinal pathogenic Escherichia coli (ExPEC) causing several diseases in humans. Such pathogens in healthy chickens can also contaminate chicken carcasses at the slaughter and then are transmitted to humans via food supply; however, reports about the ExPEC in healthy chickens are still rare. In this study, we determined the prevalence and characteristics of ExPEC isolates in healthy chickens in China. A total of 926 E. coli isolates from seven layer farms (371 isolates), one white-feather broiler farm (78 isolates) and 17 live poultry markets (477 isolates from yellow-feather broilers) in 10 cities in China, were isolated and analyzed for antibiotic resistance phenotypes and genotypes. The molecular detection of ExPEC among these healthy chicken E. coli isolates was performed by PCRs, and the serogroups and antibiotic resistance characteristics of ExPEC were also analyzed. Pulsed-field gel electrophoresis (PFGE) and Multilocus sequence typing (MLST) were used to analyze the genetic relatedness of these ExPEC isolates. We found that the resistance rate for each of the 15 antimicrobials tested among E. coli from white-feather broilers was significantly higher than that from brown-egg layers and that from yellow-feather broilers in live poultry markets (p < 0.05). A total of 22 of the 926 E. coli isolates (2.4%) from healthy chickens were qualified as ExPEC, and the detection rate (7.7%, 6/78) of ExPEC among white-feather broilers was significantly higher than that (1.6%, 6/371) from brown-egg layers and that (2.1%, 10/477) from yellow-feather broilers (p < 0.05). PFGE and MLST analysis indicated that clonal dissemination of these ExPEC isolates was unlikely. Serogroup O78 was the most predominant type among the six serogroups identified in this study, and all the six serogroups had been frequently reported in human ExPEC isolates in many countries. All the 22 ExPEC isolates were multidrug-resistant (MDR) and the resistance rates to ampicillin (100%) and sulfamethoxazole-trimethoprim (100%) were the highest, followed by tetracycline (95.5%) and doxycycline (90.9%). blaCTX-M was found in 15 of the 22 ExPEC isolates including 10 harboring additional fosfomycin resistance gene fosA3. Notably, plasmid-borne colistin resistance gene mcr-1 was identified in six ExPEC isolates in this study. Worryingly, two ExPEC isolates were found to carry both mcr-1 and blaNDM, compromising both the efficacies of carbapenems and colistin. The presence of ExPEC isolates in healthy chickens, especially those carrying mcr-1 and/or blaNDM, is alarming and will pose a threat to the health of consumers. To our knowledge, this is the first report of mcr-1-positive ExPEC isolates harboring blaNDM from healthy chickens.

The Intestinal Carriage of Plasmid-Mediated Colistin-Resistant Enterobacteriaceae in Tertiary Care Settings.

Background: In order to estimate the prevalence of plasmid borne colistin resistance and to characterize in detail the mcr-positive isolates, we carried out a sentinel testing survey on the intestinal carriage of plasmid-mediated colistin-resistant Enterobacteriaceae in hospitalized patients. Methods: Between June 2018 and September 2019, 1922 faecal samples from hospitalised patients were analysed by selective culture in presence of colistin (3.5 mg/L), and in parallel by direct detection of the mcr-1 to mcr-8 genes by qPCR. The mcr-positive isolates were characterised by whole-genome sequencing. Results: The prevalence of the mcr-1 gene was 0.21% (n = 4/1922); the mcr-2 to 8 genes were not detected. The mcr-1 gene was found to be localised in the IncX4 (n = 3) and IncHI2 (n = 1) plasmid type. One Escherichia coli isolate was susceptible to colistin due to the inactivation of the mcr-1 gene through the insertion of the IS2 element; however, the colistin resistance was inducible by culture in low concentrations of colistin. One human mcr-1 positive E. coli isolate was related genetically to the mcr-1 E. coli isolate derived from turkey meat of Czech origin. Conclusions: mcr-mediated colistin resistance currently poses little threat to patients hospitalised in Czech healthcare settings. The presence of the mcr-1 gene in the human population has a possible link to domestically produced, retail meat.

Potential Mobilization of mcr-10 by an Integrative Mobile Element via Site-Specific Recombination in Cronobacter sakazakii.

mcr-10 is a newly identified plasmid-borne colistin resistance gene, but its mobilization mechanism remains unclear. In this study, mcr-10 was found on an IncFIB plasmid carrying virulence genes mrkABCDFJ, iucABCD/iutA, and eitCBAD in a Cronobacter sakazakii isolate. By comparison with closely related plasmids, two recombination sites were identified flanking the genetic element containing mcr-10 and an integrase-encoding gene, suggesting that site-specific recombination mediated by an integrase of an integrative mobile element is a potential mechanism for mobilizing mcr-10.

Draft Genome Sequences of Multidrug-Resistant and mcr-1.1-Harboring Escherichia coli Isolated from Drinking and Well Waters Used in Syrian Refugee Camps.

Resistance to colistin, a last-resort antibiotic, threatens the treatment of complicated infections, especially in susceptible populations such as Syrian refugees who live in makeshift camps. Two multidrug-resistant Escherichia coli strains with the plasmid-borne colistin resistance gene (mcr-1.1) were isolated from the waters used by refugees and sequenced to analyze antibiotic resistance determinants.

Acquisition of Plasmid-Mediated Colistin Resistance Gene mcr-1 in Escherichia coli of Livestock Origin in Bangladesh.

Aims: To investigate plasmid-borne colistin resistance mechanism (plasmid-mediated colistin resistance [mcr-1]) in Escherichia coli of human, veterinary, and environmental origin in Bangladesh. Materials and methods: A total of 810 samples were collected from different sources. Isolation and identification of E. coli was performed using classical bacteriology and then tested for antimicrobial susceptibility. Colistin-resistant isolates were further analyzed for mcr-1 gene using PCR. Minimum inhibitory concentration (MIC) was determined using microbroth dilution technique. After sequencing of mcr-1 gene, phylogenetics was conducted to see the relationship with other mcr-1 gene sequences. Results: A total of 358 E. coli were isolated from 810 samples of humans, animals, environment, and food in Bangladesh. Of them 49 (15.9%) isolates were phenotypically resistant to colistin and 254 (70.9%) were resistant to multiple antimicrobials. mcr-1 gene was detected in three E. coli isolates of poultry source. For the three mcr-1 positive isolates the MIC of colistin sulfate was 4, 8, and 128 μg/mL. Gene sequencing of two of the three mcr-1 positive isolates and phylogenetic analysis showed close similarities of one isolate to other mcr-1 sequences available at GenBank while the other appeared to have evolved locally. Conclusion: First-ever report on circulation of mcr-1 E. coli of livestock origin in Bangladesh.