Emergence of plasmid-mediated high-level tigecycline resistance genes in animals and humans. - Related Documents




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158501.0000Emergence of plasmid-mediated high-level tigecycline resistance genes in animals and humans. Tigecycline is a last-resort antibiotic that is used to treat severe infections caused by extensively drug-resistant bacteria. tet(X) has been shown to encode a flavin-dependent monooxygenase that modifies tigecycline(1,2). Here, we report two unique mobile tigecycline-resistance genes, tet(X3) and tet(X4), in numerous Enterobacteriaceae and Acinetobacter that were isolated from animals, meat for consumption and humans. Tet(X3) and Tet(X4) inactivate all tetracyclines, including tigecycline and the newly FDA-approved eravacycline and omadacycline. Both tet(X3) and tet(X4) increase (by 64-128-fold) the tigecycline minimal inhibitory concentration values for Escherichia coli, Klebsiella pneumoniae and Acinetobacter baumannii. In addition, both Tet(X3) (A. baumannii) and Tet(X4) (E. coli) significantly compromise tigecycline in in vivo infection models. Both tet(X3) and tet(X4) are adjacent to insertion sequence ISVsa3 on their respective conjugative plasmids and confer a mild fitness cost (relative fitness of >0.704). Database mining and retrospective screening analyses confirm that tet(X3) and tet(X4) are globally present in clinical bacteria-even in the same bacteria as bla(NDM-1), resulting in resistance to both tigecycline and carbapenems. Our findings suggest that both the surveillance of tet(X) variants in clinical and animal sectors and the use of tetracyclines in food production require urgent global attention.201931133751
158410.9998Molecular mechanisms and genomic basis of tigecycline-resistant Enterobacterales from swine slaughterhouses. The continuous emergence of tigecycline-resistant bacteria is undermining the effectiveness of clinical tigecycline. Environmental tigecycline-resistant bacteria have the potential to infect humans through human-environment interactions. Furthermore, the mechanisms of tigecycline resistance in Enterobacterales are complicated. In this study, we aimed to investigate the additional pathways of tigecycline resistance in environmental Enterobacterales besides tet(X) and tmexCD-toprJ. During the years 2019-2020, tigecycline-resistant Enterobacterales (n = 45) negative for tet(X) and tmexCD-toprJ were recovered from 328 different samples from two slaughterhouses. Five distinct bacteria species were identified, of which Klebsiella pneumoniae (n = 37) was the most common, with K. pneumoniae ST45 and ST35 being the predominant clones. Tigecycline resistance determinants analysis showed that tet(A) mutations and ramR inactivation were the most prevalent mechanisms for tigecycline resistance in the 45 strains. Two known tet(A) variants (type 1 and tet(A)-v) and one novel tet(A) variant (type 3) were identified. Cloning experiments confirmed that the novel type 3 tet(A) could enhance the 4-fold MIC for tigecycline. Inactivation of ramR was induced by either point mutations or indels of sequences, which could result in the overexpression of AcrAB pump genes leading to tigecycline resistance. In addition, all isolates were resistant to a wide range of antimicrobials and carried various resistance genes. These findings enriched the epidemiological and genomic characterizations of tigecycline-resistant Enterobacterales from slaughterhouses and contributed to a better understanding of the complex mechanisms of tigecycline resistance in environmental bacteria.202235985220
158220.9998Integrated Genomic and Phenotypic Characterization of an Mcr-10.1-Harboring Multidrug Resistant Escherichia coli Strain From Migratory Birds in China. Background: The global rise in antibiotic resistance among multidrug resistant (MDR) Gram-negative (GN) bacteria has posed significant health challenges, leading to the resurgence of colistin as a key defense against these bacteria. However, the widespread use of colistin has resulted in the rapid emergence of colistin resistance on a global scale. Ten members of the (mobile colistin resistance) mcr gene family, mcr-1 through mcr-10, have been reported and documented. Currently, bacteria reported to carry the mcr-10.1 gene are sensitive to colistin, but the mechanism underlying the low-level resistance phenomenon mediated by mcr-10.1 remains unclear. Methods: In this study, antimicrobial susceptibility testing (AST) was conducted on Escherichia coli (E.coli) isolated from Chinese migratory birds, resulting in the selection of 87 strains exhibiting MDR phenotypes. Whole-genome sequencing (draft) was performed on these 87 MDR E. coli strains, and for one of the E. coli strains carrying the mcr-10.1 gene, whole-genome sequencing, phenotypic characterization, AST and conjugation experiments were conducted to identify its resistance phenotypes and genetic characteristics. Results: Whole-genome sequencing (draft) of 87 MDR E. coli isolates revealed a diverse array of resistance genes, predominantly including aminoglycoside, β-lactam, tetracycline, and sulfonamide resistance genes. Remarkably, one isolate, despite being sensitive to colistin, harbored the mcr-10.1 gene. Further sequencing showed that mcr-10.1 was located in the conserved region of xerC-mcr-10.1, a hotspot for movable elements with various insertion sequences (ISs) or transposons nearby. Phenotypic characterization indicated that the MDR plasmid pGN25-mcr10.1 had no significant effect on the growth of GN25 and its derivatives but reduced the number of bacterial flagella. Conclusions: It is particularly important to note that bacteria harboring the mcr-10.1 gene may exhibit low minimum inhibitory concentration (MIC) values, but that the MIC values under colistin selective pressure can become progressively higher and exacerbate the difficulty of treating infections caused by mcr-10.1-associated bacteria. Therefore, vigilance for such "silent transmission" is warranted, and continuous monitoring of the spread of mcr-10.1 is necessary in the future.202540343190
495230.9998Plasmid-encoded tet(X) genes that confer high-level tigecycline resistance in Escherichia coli. Tigecycline is one of the last-resort antibiotics to treat complicated infections caused by both multidrug-resistant Gram-negative and Gram-positive bacteria(1). Tigecycline resistance has sporadically occurred in recent years, primarily due to chromosome-encoding mechanisms, such as overexpression of efflux pumps and ribosome protection(2,3). Here, we report the emergence of the plasmid-mediated mobile tigecycline resistance mechanism Tet(X4) in Escherichia coli isolates from China, which is capable of degrading all tetracyclines, including tigecycline and the US FDA newly approved eravacycline. The tet(X4)-harbouring IncQ1 plasmid is highly transferable, and can be successfully mobilized and stabilized in recipient clinical and laboratory strains of Enterobacteriaceae bacteria. It is noteworthy that tet(X4)-positive E. coli strains, including isolates co-harbouring mcr-1, have been widely detected in pigs, chickens, soil and dust samples in China. In vivo murine models demonstrated that the presence of Tet(X4) led to tigecycline treatment failure. Consequently, the emergence of plasmid-mediated Tet(X4) challenges the clinical efficacy of the entire family of tetracycline antibiotics. Importantly, our study raises concern that the plasmid-mediated tigecycline resistance may further spread into various ecological niches and into clinical high-risk pathogens. Collective efforts are in urgent need to preserve the potency of these essential antibiotics.201931235960
157340.9998Genomic Analysis of a Pan-Resistant Isolate of Klebsiella pneumoniae, United States 2016. Antimicrobial resistance is a threat to public health globally and leads to an estimated 23,000 deaths annually in the United States alone. Here, we report the genomic characterization of an unusual Klebsiella pneumoniae, nonsusceptible to all 26 antibiotics tested, that was isolated from a U.S. PATIENT: The isolate harbored four known beta-lactamase genes, including plasmid-mediated bla(NDM-1) and bla(CMY-6), as well as chromosomal bla(CTX-M-15) and bla(SHV-28), which accounted for resistance to all beta-lactams tested. In addition, sequence analysis identified mechanisms that could explain all other reported nonsusceptibility results, including nonsusceptibility to colistin, tigecycline, and chloramphenicol. Two plasmids, IncA/C2 and IncFIB, were closely related to mobile elements described previously and isolated from Gram-negative bacteria from China, Nepal, India, the United States, and Kenya, suggesting possible origins of the isolate and plasmids. This is one of the first K. pneumoniae isolates in the United States to have been reported to the Centers for Disease Control and Prevention (CDC) as nonsusceptible to all drugs tested, including all beta-lactams, colistin, and tigecycline.IMPORTANCE Antimicrobial resistance is a major public health threat worldwide. Bacteria that are nonsusceptible or resistant to all antimicrobials available are of major concern to patients and the public because of lack of treatment options and potential for spread. A Klebsiella pneumoniae strain that was nonsusceptible to all tested antibiotics was isolated from a U.S. PATIENT: Mechanisms that could explain all observed phenotypic antimicrobial resistance phenotypes, including resistance to colistin and beta-lactams, were identified through whole-genome sequencing. The large variety of resistance determinants identified demonstrates the usefulness of whole-genome sequencing for detecting these genes in an outbreak response. Sequencing of isolates with rare and unusual phenotypes can provide information on how these extremely resistant isolates develop, including whether resistance is acquired on mobile elements or accumulated through chromosomal mutations. Moreover, this provides further insight into not only detecting these highly resistant organisms but also preventing their spread.201829615503
188950.9997Widespread Dissemination of Plasmid-Mediated Tigecycline Resistance Gene tet(X4) in Enterobacterales of Porcine Origin. The emergence of the plasmid-mediated high levels of the tigecycline resistance gene has drawn worldwide attention and has posed a major threat to public health. In this study, we investigated the prevalence of the tet(X4)-positive Enterobacterales isolates collected from a pig slaughterhouse and farms. A total of 101 tigecycline resistance strains were isolated from 353 samples via a medium with tigecycline, of which 33 carried tet(X4) (9.35%, 33/353) and 2 carried tet(X6) (0.57%, 2/353). These strains belong to seven different species, with Escherichia coli being the main host bacteria. Importantly, this report is the first one to demonstrate that tet(X4) was observed in Morganella morganii. Whole-genome sequencing results revealed that tet(X4)-positive bacteria can coexist with other resistance genes, such as bla(NDM-1) and cfr. Additionally, we were the first to report that tet(X4) and bla(NDM-1) coexist in a Klebsiella quasipneumoniae strain. The phylogenetic tree of 533 tet(X4)-positive E. coli strains was constructed using 509 strains from the NCBI genome assembly database and 24 strains from this study, which arose from 8 sources and belonged to 135 sequence types (STs) worldwide. We used Nanopore sequencing to interpret the selected 21 nonclonal and representative strains and observed that 19 tet(X4)-harboring plasmids were classified into 8 replicon types, and 2 tet(X6) genes were located on integrating conjugative elements. A total of 68.42% of plasmids carrying tet(X4) were transferred successfully with a conjugation frequency of 10(-2) to 10(-7). These findings highlight that diverse plasmids drive the widespread dissemination of the tigecycline resistance gene tet(X4) in Enterobacterales of porcine origin. IMPORTANCE Tigecycline is considered to be the last resort of defense against diseases caused by broad-spectrum resistant Gram-negative bacteria. In this study, we systematically analyzed the prevalence and genetic environments of the resistance gene tet(X4) in a pig slaughterhouse and farms and the evolutionary relationship of 533 tet(X4)-positive Escherichia coli strains, including 509 tet(X4)-positive E. coli strains selected from the 27,802 assembled genomes of E. coli from the NCBI between 2002 and 2022. The drug resistance of tigecycline is widely prevalent in pig farms where tetracycline is used as a veterinary drug. This prevalence suggests that pigs are a large reservoir of tet(X4) and that tet(X4) can spread horizontally through the food chain via mobile genetic elements. Furthermore, tetracycline resistance may drive tigecycline resistance through some mechanisms. Therefore, it is important to monitor tigecycline resistance, develop effective control measures, and focus on tetracycline use in the pig farms.202236125305
158360.9997Identification of Novel Mobilized Colistin Resistance Gene mcr-9 in a Multidrug-Resistant, Colistin-Susceptible Salmonella enterica Serotype Typhimurium Isolate. Mobilized colistin resistance (mcr) genes are plasmid-borne genes that confer resistance to colistin, an antibiotic used to treat severe bacterial infections. To date, eight known mcr homologues have been described (mcr-1 to -8). Here, we describe mcr-9, a novel mcr homologue detected during routine in silico screening of sequenced Salmonella genomes for antimicrobial resistance genes. The amino acid sequence of mcr-9, detected in a multidrug-resistant (MDR) Salmonella enterica serotype Typhimurium (S Typhimurium) strain isolated from a human patient in Washington State in 2010, most closely resembled mcr-3, aligning with 64.5% amino acid identity and 99.5% coverage using Translated Nucleotide BLAST (tblastn). The S. Typhimurium strain was tested for phenotypic resistance to colistin and was found to be sensitive at the 2-mg/liter European Committee on Antimicrobial Susceptibility Testing breakpoint under the tested conditions. mcr-9 was cloned in colistin-susceptible Escherichia coli NEB5α under an IPTG (isopropyl-β-d-thiogalactopyranoside)-induced promoter to determine whether it was capable of conferring resistance to colistin when expressed in a heterologous host. Expression of mcr-9 conferred resistance to colistin in E. coli NEB5α at 1, 2, and 2.5 mg/liter colistin, albeit at a lower level than mcr-3 Pairwise comparisons of the predicted protein structures associated with all nine mcr homologues (Mcr-1 to -9) revealed that Mcr-9, Mcr-3, Mcr-4, and Mcr-7 share a high degree of similarity at the structural level. Our results indicate that mcr-9 is capable of conferring phenotypic resistance to colistin in Enterobacteriaceae and should be immediately considered when monitoring plasmid-mediated colistin resistance.IMPORTANCE Colistin is a last-resort antibiotic that is used to treat severe infections caused by MDR and extensively drug-resistant (XDR) bacteria. The World Health Organization (WHO) has designated colistin as a "highest priority critically important antimicrobial for human medicine" (WHO, Critically Important Antimicrobials for Human Medicine, 5th revision, 2017, https://www.who.int/foodsafety/publications/antimicrobials-fifth/en/), as it is often one of the only therapies available for treating serious bacterial infections in critically ill patients. Plasmid-borne mcr genes that confer resistance to colistin pose a threat to public health at an international scale, as they can be transmitted via horizontal gene transfer and have the potential to spread globally. Therefore, the establishment of a complete reference of mcr genes that can be used to screen for plasmid-mediated colistin resistance is essential for developing effective control strategies.201931064835
191870.9997Molecular Detection of Class 1 Integron-Associated Gene Cassettes in KPC-2-Producing Klebsiella pneumoniae Clones by Whole-Genome Sequencing. The dissemination of antimicrobial resistance genes and the bacterium that harbor them have increasingly become a public concern, especially in low- and middle-income countries. The present study used whole-genome sequencing to analyze 10 KPC-2-producing Klebsiella pneumoniae isolates obtained from clinical specimens originated from Brazilian hospitals. The study documents a relevant "snapshot" of the presence of class 1 integrons in 90% of the strains presenting different gene cassettes (dfrA30, dfrA15, dfrA12, dfrA14, aadA1, aadA2, and aac(6')Iq), associated or not with transposons. Two strains presented nonclassical integron (lacking the normal 3'conserved segment). In general, most strains showed a complex resistome, characterizing them as highly resistant. Integrons, a genetically stable and efficient system, confer to bacteria as highly adaptive and low cost evolution potential to bacteria, even more serious when associated with high-risk clones, indicating an urgent need for control and prevention strategies to avoid the spread of resistance determinants in Brazil. Despite this, although the class 1 integron identified in the KPC-2-producing K. pneumoniae clones is important, our findings suggest that other elements probably have a greater impact on the spread of antimicrobial resistance, since many of these important genes were not related to this cassette.201931074706
177380.9997Detection of SXT/R391 integrative conjugative elements carrying tigecycline resistance genes in Shewanella spp. isolated from retail seafood. Tigecycline is a last resort antibiotic that is used to treat serious infections; however, some bacteria have developed tigecycline resistance by producing a tigecycline-inactivating enzyme or tigecycline resistance efflux pump, encoded by tet(X) and tmexCD-toprJ genes, respectively. Tons of seafood are consumed annually in China; however, whether seafood harbors tigecycline-resistant bacteria is not known. In this study, we isolated various tigecycline-resistant bacteria from retail seafood; among these, Shewanella was the predominant tigecycline-resistant genus (33/76, 43.4%). Genomic sequencing revealed that two Shewanella strains carried the tet(X4) gene, while one Shewanella chilikensis strain co-harbored tmexCD2-toprJ2 and bla(NDM-1) genes. The tet(X4) and tmexCD2-toprJ2 were found to be located on novel members of the SXT/R391 family of integrated conjugative elements (ICEs). As per our knowledge, this is the first report on the emergence of SXT/R391 ICEs carrying tet(X4) or tmexCD2-toprJ2 gene in Shewanella strains. The SXT/R391 family ICEs could mediate the spread of tigecycline resistance genes among aquatic bacteria, and contact between seafood and consumers may lead to the dissemination of tigecycline-resistant bacteria. Our study revealed that Shewanella spp. may act as potential reservoirs of tigecycline resistance genes.202540569748
189890.9997Multiple-Replicon Resistance Plasmids of Klebsiella Mediate Extensive Dissemination of Antimicrobial Genes. Multiple-replicon resistance plasmids have become important carriers of resistance genes in Gram-negative bacteria, and the evolution of multiple-replicon plasmids is still not clear. Here, 56 isolates of Klebsiella isolated from different wild animals and environments between 2018 and 2020 were identified by phenotyping via the micro-broth dilution method and were sequenced and analyzed for bacterial genome-wide association study. Our results revealed that the isolates from non-human sources showed more extensive drug resistance and especially strong resistance to ampicillin (up to 80.36%). The isolates from Malayan pangolin were particularly highly resistant to cephalosporins, chloramphenicol, levofloxacin, and sulfamethoxazole. Genomic analysis showed that the resistance plasmids in these isolates carried many antibiotic resistance genes. Further analysis of 69 plasmids demonstrated that 28 plasmids were multiple-replicon plasmids, mainly carrying beta-lactamase genes such as bla (CTX-M-) (15), bla (CTX-M-) (14), bla (CTX-M-) (55), bla (OXA-) (1), and bla (TEM-) (1). The analysis of plasmids carried by different isolates showed that Klebsiella pneumoniae might be an important multiple-replicon plasmid host. Plasmid skeleton and structure analyses showed that a multiple-replicon plasmid was formed by the fusion of two or more single plasmids, conferring strong adaptability to the antibiotic environment and continuously increasing the ability of drug-resistant isolates to spread around the world. In conclusion, multiple-replicon plasmids are better able to carry resistance genes than non-multiple-replicon plasmids, which may be an important mechanism underlying bacterial responses to environments with high-antibiotic pressure. This phenomenon will be highly significant for exploring bacterial resistance gene transmission and diffusion mechanisms in the future.202134777312
1644100.9997Emergence of plasmid-mediated tigecycline resistance tet(X4) gene in Enterobacterales isolated from wild animals in captivity. BACKGROUND: Over the past few decades, antimicrobial resistance (AMR) has emerged as a global health challenge in human and veterinary medicine. Research on AMR genes in captive wild animals has increased. However, the presence and molecular characteristics of tet(X)-carrying bacteria in these animals remain unknown. METHODS: Eighty-four samples were collected from captive wild animals. tet(X) variants were detected using polymerase chain reaction and the isolates were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. All isolated strains were subjected to antimicrobial susceptibility testing and whole-genome sequencing. The virulence of an Escherichia coli strain carrying enterotoxin genes was assessed using a Galleria mellonella larval model. RESULTS: We isolated two tet(X4)-positive E. coli strains and one tet(X4)-positive Raoultella ornithinolytica strain. Antimicrobial susceptibility tests revealed that all three tet(X4)-carrying bacteria were sensitive to the 13 tested antimicrobial agents, but exhibited resistance to tigecycline. Notably, one tet(X4)-carrying E. coli strain producing an enterotoxin had a toxic effect on G. mellonella larvae. Whole-genome sequencing analysis showed that the two tet(X4)-carrying E. coli strains had more than 95% similarity to tet(X4)-containing E. coli strains isolated from pigs and humans in China. CONCLUSION: The genetic environment of tet(X4) closely resembled that of the plasmid described in previous studies. Our study identified tet(X4)-positive strains in wildlife and provided valuable epidemiological data for monitoring drug resistance. The identification of enterotoxin-producing E. coli strains also highlights the potential risks posed by virulence genes.202439077391
1890110.9997Emergence and Characterization of Tigecycline Resistance Gene tet(X4) in ST609 Escherichia coli Isolates from Wastewater in Turkey. Emergence of pathogens harboring tigecycline resistance genes incurs great concerns. Wastewater is recognized as the important reservoir of antimicrobial resistance genes. Here we characterized the phenotypes and genotypes of bacteria carrying tet(X4) from wastewater in Turkey for the first time. Four tet(X4)-positive Escherichia coli isolates were identified and characterized by PCR, Sanger sequencing, antimicrobial susceptibility testing, conjugation assays, Illumina sequencing, nanopore sequencing and bioinformatic analysis. Four tet(X4)-harboring isolates were multidrug-resistant (MDR) bacteria and the tet(X4) gene was nontransferable in four isolates. Genetic analysis revealed that tet(X4) genes in four isolates were located on plasmids co-harboring two replicons IncFIA(HI1) and IncFIB(K). However, none of the four plasmids carried genes associated with horizontal transfer of plasmids. The coexistence of bla(SHV-12)-bearing IncX3-type plasmid and tet(X4)-harboring plasmid was also found in one isolate. These findings indicate that continuous surveillance of the tet(X4)-bearing isolates in different environments worldwide should be strengthened. IMPORTANCE The emergence of tigecycline resistance genes in humans and animals in China seriously threatens the clinical utility of tigecycline, but the molecular epidemiology of tigecycline-resistant bacteria in other countries remained largely unknown. Therefore, it is necessary to learn the prevalence and molecular characteristics of bacteria carrying tigecycline resistance genes, particularly the mobilizable tet(X4), in other countries. In the study, we first described the presence and molecular characteristics of the tet(X4)-positive E. coli isolates from wastewater in Turkey. Four tet(X4)-bearing isolates belonged to ST609, an E. coli clone commonly found from humans, animals and the environment. These findings highlight the importance of monitoring the tet(X4) gene in different settings globally.202235863037
1894120.9997Phenotypic and Genotypic Characterization of Multidrug-Resistant Enterobacter hormaechei Carrying qnrS Gene Isolated from Chicken Feed in China. Multidrug resistance (MDR) in Enterobacteriaceae including resistance to quinolones is rising worldwide. The plasmid-mediated quinolone resistance (PMQR) gene qnrS is prevalent in Enterobacteriaceae. However, the qnrS gene is rarely found in Enterobacter hormaechei (E. hormaechei). Here, we reported one multidrug resistant E. hormaechei strain M1 carrying the qnrS1 and bla(TEM-1) genes. This study was to analyze the characteristics of MDR E. hormaechei strain M1. The E. hormaechei strain M1 was identified as Enterobacter cloacae complex by biochemical assay and 16S rRNA sequencing. The whole genome was sequenced by the Oxford Nanopore method. Taxonomy of the E. hormaechei was based on multilocus sequence typing (MLST). The qnrS with the other antibiotic resistance genes were coexisted on IncF plasmid (pM1). Besides, the virulence factors associated with pathogenicity were also located on pM1. The qnrS1 gene was located between insertion element IS2A (upstream) and transposition element ISKra4 (downstream). The comparison result of IncF plasmids revealed that they had a common plasmid backbone. Susceptibility experiment revealed that the E. hormaechei M1 showed extensive resistance to the clinical antimicrobials. The conjugation transfer was performed by filter membrane incubation method. The competition and plasmid stability assays suggested the host bacteria carrying qnrS had an energy burden. As far as we know, this is the first report that E. hormaechei carrying qnrS was isolated from chicken feed. The chicken feed and poultry products could serve as a vehicle for these MDR bacteria, which could transfer between animals and humans through the food chain. We need to pay close attention to the epidemiology of E. hormaechei and prevent their further dissemination. IMPORTANCE Enterobacter hormaechei is an opportunistic pathogen. It can cause infections in humans and animals. Plasmid-mediated quinolone resistance (PMQR) gene qnrS can be transferred intergenus, which is leading to increase the quinolone resistance levels in Enterobacteriaceae. Chicken feed could serve as a vehicle for the MDR E. hormaechei. Therefore, antibiotic-resistance genes (ARGs) might be transferred to the intestinal flora after entering the gastrointestinal tract with the feed. Furthermore, antibiotic-resistant bacteria (ARB) were also excreted into environment with feces, posing a huge threat to public health. This requires us to monitor the ARB and antibiotic-resistant plasmids in the feed. Here, we demonstrated the characteristics of one MDR E. hormaechei isolate from chicken feed. The plasmid carrying the qnrS gene is a conjugative plasmid with transferability. The presence of plasmid carrying antibiotic-resistance genes requires the maintenance of antibiotic pressure. In addition, the E. hormaechei M1 belonged to new sequence type (ST). These data show the MDR E. hormaechei M1 is a novel strain that requires our further research.202235467399
1893130.9997Genetic analysis of the first mcr-1 positive Escherichia coli isolate collected from an outpatient in Chile. Global dissemination of mcr-like genes represents a serious threat to public health since it jeopardizes the effectiveness of colistin, an antibiotic used as a last-resort treatment against highly antibiotic-resistant bacteria. In 2017, a mcr-1-positive isolate of Escherichia coli was found in Chile for the first time. Herein we report the genetic features of this strain (UCO-457) by whole-genome sequencing (WGS) and conjugation experiments. The UCO-457 strain belonged to ST4204 and carried a 285 kb IncI2-type plasmid containing the mcr-1 gene. Moreover, this plasmid was transferred by conjugation to an E. coli J53 strain at high frequency. The isolate harbored the cma, iroN, and iss virulence genes and did carry resistance genes to trimethoprim/sulfamethoxazole and fluoroquinolones. Other antibiotic resistance determinants such as β-lactamases-encoding genes were not detected, making the isolate highly susceptible to these antibiotics. Our results revealed that such susceptible isolates could be acting as platforms to disseminate plasmid-mediated colistin resistance. Based on this evidence, we consider that mcr-like prevalence deserves urgent attention and should be examined not only in highly resistant bacteria but also in susceptible isolates.201931228460
1892140.9997Colistin Resistance Mediated by Mcr-3-Related Phosphoethanolamine Transferase Genes in Aeromonas Species Isolated from Aquatic Environments in Avaga and Pakro Communities in the Eastern Region of Ghana. PURPOSE: Colistin is classified by the World Health Organization (WHO) as a critically important and last-resort antibiotic for the treatment of infections caused by carbapenem-resistant bacteria. However, colistin resistance mediated by chromosomal mutations or plasmid-linked mobilized colistin resistance (mcr) genes has emerged. METHODS: Thirteen mcr-positive Aeromonas species isolated from water samples collected in Eastern Ghana were analyzed using whole-genome sequencing (WGS). Antimicrobial susceptibility was tested using the broth microdilution method. Resistome analysis was performed in silico using a web-based platform. RESULTS: The minimum inhibitory concentration (MIC) of colistin for all except three isolates was >4 µg/mL. Nine new sequence types were identified and whole-genome analysis revealed that the isolates harbored genes (mcr-3-related genes) that code for Lipid A phosphoethanolamine transferases on their chromosomes. BLAST analysis indicated that the amino acid sequences of the mcr-3-related genes detected varied from those previously reported and shared 79.04-99.86% nucleotide sequence identity with publicly available mcr-3 variants and mcr-3-related phosphoethanolamine transferases. Analysis of the genetic context of mcr-3-related genes revealed that the genetic environment surrounding mcr-3-related genes was diverse among the different species of Aeromonas but conserved among isolates of the same species. Mcr-3-related-gene-IS-mcr-3-related-gene segment was identified in three Aeromonas caviae strains. CONCLUSION: The presence of mcr-3-related genes close to insertion elements is important for continuous monitoring to better understand how to control the mobilization and dissemination of antibiotic resistance genes.202439050833
1599150.9997Colistin Resistance Genes in Broiler Chickens in Tunisia. Colistin is a polymyxin antibiotic that has been used in veterinary medicine for decades, as a treatment for enterobacterial digestive infections as well as a prophylactic treatment and growth promoter in livestock animals, leading to the emergence and spread of colistin-resistant Gram-negative bacteria and to a great public health concern, considering that colistin is one of the last-resort antibiotics against multidrug-resistant deadly infections in clinical practice. Previous studies performed on livestock animals in Tunisia using culture-dependent methods highlighted the presence of colistin-resistant Gram-negative bacteria. In the present survey, DNA extracted from cloacal swabs from 195 broiler chickens from six farms in Tunisia was tested via molecular methods for the ten mobilized colistin resistance (mcr) genes known so far. Of the 195 animals tested, 81 (41.5%) were mcr-1 positive. All the farms tested were positive, with a prevalence ranging from 13% to 93%. These results confirm the spread of colistin resistance in livestock animals in Tunisia and suggest that the investigation of antibiotic resistance genes by culture-independent methods could be a useful means of conducting epidemiological studies on the spread of antimicrobial resistance.202337106971
1846160.9997Epidemiology and Traits of Mobile Colistin Resistance (mcr) Gene-Bearing Organisms from Horses. Mobile colistin resistance (mcr) genes (mcr-1 to mcr-10) threaten the efficacy of colistin (COL), a polymyxin antibiotic that is used as a last-line agent for the treatment of deadly infections caused by multidrug-resistant and extensively drug-resistant bacteria in humans and animals. COL has been used for more than 60 years for the prophylactic control and treatment of infections in livestock husbandry but not in horses. Polymyxin B is used for the prophylactic control and empirical treatment of infections in horses without conducting sensitivity tests. The lack of sensitivity testing exerts selection pressure for the acquisition of the mcr gene. By horizontal transfer, mcr-1, mcr-5, and mcr-9 have disseminated among horse populations globally and are harbored by Escherichia coli, Klebsiella, Enterobacter, Citrobacter, and Salmonella species. Conjugative plasmids, insertion sequences, and transposons are the backbone of mcr genes in the isolates, which co-express genes conferring multi- to extensive-drug resistance, including genes encoding extended-spectrum β-lactamase, ampicillinase C, fosfomycin, and fluoroquinolone resistance, and virulence genes. The transmission of mcr genes to/among bacterial strains of equine origin is non-clonal. Contact with horses, horse manure, feed/drinking water, farmers, farmers' clothing/farm equipment, the consumption of contaminated horse meat and its associated products, and the trading of horses, horse meat, and their associated products are routes for the transmission of mcr-gene-bearing bacteria in, to, and from the equine industry.202235893557
1689170.9997Occurrence and Characteristics of Mcrs among Gram-Negative Bacteria Causing Bloodstream Infections of Infant Inpatients between 2006 and 2019 in China. The aim of this study was to determine the occurrence of mobilized colistin resistance (mcr) genes in Gram-negative bacteria causing bloodstream infections of child inpatients in China. Bacteria were collected between 2006 and 2019 in a maternal and child health hospital, and mcr genes were screened by PCR. Five of 252 isolates were mcr-positive, including one mcr-1-positive colistin-resistant Escherichia coli isolate, two mcr-9-positive colistin-susceptible Salmonella enterica isolates, and two mcr-9-positive colistin-susceptible Enterobacter hormaechei isolates. These were obtained from two neonate and three infant patients admitted between 2009 and 2018. The E. coli isolate was obtained from a neonate aged 20 min, suggestive of a possible mother-to-neonate transmission. The five mcr-positive isolates were multidrug resistant, and two S. enterica and one E. hormaechei isolate showed a hypervirulent phenotype compared to a hypervirulent Klebsiella pneumoniae type strain in a Galleria mellonella infection model. The mcr-1 gene was carried by an IncX4-type pA1-like epidemic plasmid, and the mcr-9 gene was detected on IncHI2/2A-type novel plasmids co-carrying multiple resistance genes. The four IncHI2/2A-type plasmids shared a backbone and a high similarity (≥77% coverage and ≥ 90% nucleotide identity), suggesting that they were derived from a common ancestor with cross-species transmission and have circulated locally over a long period. The conjugation assay showed that the mcr-1-encoding plasmid and one mcr-9-encoding plasmid were self-transmissible to E. coli with high conjugation frequencies. Our findings demonstrate that mcr genes have disseminated in the community and/or hospitals, mediated by epidemic/endemic plasmids over a long period. The study shows that continuous monitoring of mcr genes is imperative for understanding and tackling their dissemination. IMPORTANCE Antimicrobial resistance, especially the spread of carbapenemase-producing Enterobacteriaceae (CPE), represents one of the largest challenges to One Health coverage of environmental, animal, and human sectors. Colistin is one of the last-line antibiotics for clinical treatment of CPE. However, the emergence of the mobilized colistin resistance (mcr) gene largely threatens the usage of colistin in the clinical setting. In this study, we investigated the existence of mcr genes in 252 Gram-negative bacteria collected between 2006 and 2019 which caused bloodstream infections of child inpatients in China. We found a high prevalence of mcr carriage among children inpatients in the absence of professional exposure, and mcr might have widely disseminated in the community via different routes. This study emphasizes the importance of rational use of colistin in the One Health frame, and highlights both the urgent need for understanding the prevalence and dissemination of mcr genes in different populations and the importance of effective measures to control their spread.202235138190
4951180.9997Aeromonas and mcr-3: A Critical Juncture for Transferable Polymyxin Resistance in Gram-Negative Bacteria. Polymyxin antibiotics B and colistin are considered drugs of last resort for the treatment of multi-drug and carbapenem-resistant Gram-negative bacteria. With the emergence and dissemination of multi-drug resistance, monitoring the use and resistance to polymyxins imparted by mobilised colistin resistance genes (mcr) is becoming increasingly important. The Aeromonas genus is widely disseminated throughout the environment and serves as a reservoir of mcr-3, posing a significant risk for the spread of resistance to polymyxins. Recent phylogenetic studies and the identification of insertion elements associated with mcr-3 support the notion that Aeromonas spp. may be the evolutionary origin of the resistance gene. Furthermore, mcr-3-related genes have been shown to impart resistance in naïve E. coli and can increase the polymyxin MIC by up to 64-fold (with an MIC of 64 mg/L) in members of Aeromonas spp. This review will describe the genetic background of the mcr gene, the epidemiology of mcr-positive isolates, and the relationship between intrinsic and transferable mcr resistance genes, focusing on mcr-3 and mcr-3-related genes.202439599474
2075190.9997Identification and Genetic Characterization of Conjugative Plasmids Encoding Coresistance to Ciprofloxacin and Cephalosporin in Foodborne Vibrio spp. Plasmid-mediated quinolone resistance (PMQR) determinants, such as qnrVC genes, have been widely reported in Vibrio spp. while other types of PMQR genes were rarely reported in these bacteria. This study characterized the phenotypic and genotypic features of foodborne Vibrio spp. carrying qnrS, a key PMQR gene in Enterobacteriaceae. Among a total of 1,811 foodborne Vibrio isolates tested, 34 (1.88%) were found to harbor the qnrS gene. The allele qnrS2 was the most prevalent, but coexistence with other qnr alleles was common. Missense mutations in the quinolone resistance-determining region (QRDR) of the gyrA and parC genes were only found in 11 of the 34 qnrS-bearing isolates. Antimicrobial susceptibility tests showed that all 34 qnrS-bearing isolates were resistant to ampicillin and that a high percentage also exhibited resistance to cefotaxime, ceftriaxone, and trimethoprim-sulfamethoxazole. Genetic analysis showed that these phenotypes were attributed to a diverse range of resistance elements that the qnrS-bearing isolates harbored. The qnrS2 gene could be found in both the chromosome and plasmids; the plasmid-borne qnrS2 genes could be found on both conjugative and nonconjugative plasmids. pAQU-type qnrS2-bearing conjugative plasmids were able to mediate expression of phenotypic resistance to both ciprofloxacin and cephalosporins. Transmission of this plasmid among Vibrio spp. would speed up the emergence of multidrug-resistant (MDR) pathogens that are resistant to the most important antibiotics used in treatment of Vibrio infections, suggesting that close monitoring of emergence and dissemination of MDR Vibrio spp. in both food samples and clinical settings is necessary. IMPORTANCE Vibrio spp. used to be very susceptible to antibiotics. However, resistance to clinically important antibiotics, such as cephalosporins and fluoroquinolones, among clinically isolated Vibrio strains is increasingly common. In this study, we found that plasmid-mediated quinolone resistance (PMQR) genes, such as qnrS, that have not been previously reported in Vibrio spp. can now be detected in food isolates. The qnrS2 gene alone could mediate expression of ciprofloxacin resistance in Vibrio spp.; importantly, this gene could be found in both the chromosome and plasmids. The plasmids that harbor the qnrS2 gene could be both conjugative and nonconjugative, among which the pAQU-type qnrS2-bearing conjugative plasmids were able to mediate expression of resistance to both ciprofloxacin and cephalosporins. Transmission of this plasmid among Vibrio spp. would accelerate the emergence of multidrug-resistant pathogens.202337395663