Mobile Colistin Resistance Gene Research Articles

Farm animals and aquaculture: significant reservoirs of mobile colistin resistance genes.

Colistin resistance has attracted substantial attention after colistin was considered as a last-resort drug for the treatment of infections caused by carbapenem-resistant and/or multidrug-resistant (MDR) Gram-negative bacteria in clinical settings. However, with the discovery of highly mobile colistin resistance (mcr) genes, colistin resistance has become an increasingly urgent issue worldwide. Despite many reviews, which summarized the prevalence, mechanisms, and structures of these genes in bacteria of human and animal origin, studies on the prevalence of mobile colistin resistance genes in aquaculture and their transmission between animals and humans remain scarce. Herein, we review recent reports on the prevalence of colistin resistance genes in animals, especially wildlife and aquaculture, and their possibility of transmission to humans via the food chain. This review also gives some insights into the routine surveillance, changing policy and replacement of polymyxins by polymyxin derivatives, molecular inhibitors, and traditional Chinese medicine to tackle colistin resistance.

Prevalence and Molecular Characteristics of Avian-Origin mcr-1-Harboring Escherichia coli in Shandong Province, China.

The objective of this study was to evaluate the prevalence and characteristics of avian-origin mcr-1-harbouring Escherichia coli in Shandong Province, China. During 2017—2018, a total of 668 non-duplicate E. coli isolates were separately collected from 8eight large intensive poultry farms in Shandong Province. Antimicrobial susceptibility testing for 10 antimicrobial agents commonly used in farms was performed on all E. coli isolates by the agar dilution method; the mobile colistin resistance gene (mcr-1) gene was screened by PCR, and mcr-1 positive isolates were PCR-screened for antimicrobial resistance genes and typed by multi-locus sequence typing (MLST). Among the 668 E. coli, 102 (15.3%) harbored the mcr-1 gene; high antimicrobial resistance rates were observed for ampicillin (100/102, 98.0%), followed by amoxicillin (99/102, 97.1%) and florfenicol (97/102, 95.1%), and a low level of resistance was found for amoxicillin/clavulanic acid (24/102, 23.5%). Five ESBL genes were detected, and all isolates carried blaTEM (102/102, 100%), followed by blaCTX–M (90/102, 88.2%). Four PMQR genes were detected; aac(6)-Ib-cr (40/102, 39.2%) was the most commonly isolated PMQR gene, followed by qnrA (10/102, 9.8%). Thirty-eight different kinds of STs were identified, and the dominant ST was ST93 (19/102, 18.6%), followed by ST48 (9/102, 8.8%). In summary, E. coli from poultry in Shandong could be a reservoir for the mcr-1 gene, which could pose serious risks to human public health.

Carriage of Distinct mcr-1-Harboring Plasmids by Unusual Serotypes of Salmonella.

Colistin acts as a last-resort antibiotic against lethal infections by carbapenem-resistant Enterobacterial pathogens. Enterobacteriaceae carrying mobile colistin resistance (MCR) genes are rapidly emerging and threatening human health and food safety. Despite mcr-1 being prevalent in Escherichia coli, its dissemination in Salmonella is not well characterized. Herein, two unusual serotypes of colistin-resistant Salmonella isolates are reported first, namely serotype Ngor (ST5399) and Goldcoast (ST2529). Using whole genome sequencing, it is shown that mcr-1 is located on the IncHI2-like plasmid pTB501 (188,527 bp) of strain SSDFZ54 and the IncX4-type plasmid pTB602 (33,303 bp) in strain SSDFZ69, respectively. Furthermore, the backbone, tra- and antimicrobial resistance genes relative variable regions in the mcr-1-bearing IncHI2 plasmids are systematically characterized. Phylogenetic analysis shows that all IncHI2-type plasmids from non-Chinese regions are clustered together, suggesting a possible Chinese origin. Taken together, these findings extend the understanding of Salmonella as a vehicle of mcr-1 carriage and distribution.

Development of a Novel mcr-6 to mcr-9 Multiplex PCR and Assessment of mcr-1 to mcr-9 Occurrence in Colistin-Resistant Salmonella enterica Isolates From Environment, Feed, Animals and Food (2011-2018) in Germany.

The polymyxin antibiotic colistin has been used in decades for treatment and prevention of infectious diseases in livestock. Nowadays, it is even considered as last-line treatment option for severe human infections caused by multidrug- and carbapenem-resistant Gram-negative bacteria. Therefore, the discovery of plasmid-mediated mobile colistin resistance (mcr) genes raised major public health concern. The aim of our study was to analyze colistin-resistant Salmonella enterica strains from animals, food, feed and the environment collected at the National Reference Laboratory for Salmonella in Germany on the presence of mcr-1 to mcr-9 genes. Altogether 407 colistin-resistant (MIC >2 mg/L) Salmonella isolates received between 2011 and 2018 were selected and screened by PCR using a published mcr-1 to mcr-5 as well as a newly developed mcr-6 to mcr-9 multiplex PCR protocol. 254 of 407 (62.4%) isolates harbored either mcr-1 (n = 175), mcr-4 (n = 53), mcr-5 (n = 18) or mcr-1 and mcr-9 (n = 8). The number of mcr-positive isolates ranged from 19 (2017) to 64 (2012) per year. WGS revealed that none of our isolates harbored the mcr-9.1 gene. Instead, two novel mcr-9 variants were observed, which both were affected by frameshift mutations and are probably non-functional. The mcr-harboring isolates were mainly derived from animals (77.2%) or food (20.1%) and could be assigned to ten different Salmonella serovars. Many of the isolates were multidrug-resistant. Co-occurrence of mcr-1 and AmpC or ESBL genes was observed in eight isolates. Our findings suggest that mcr genes are widely spread among colistin-resistant Salmonella isolates from livestock and food in Germany. Potential transfer of mcr-harboring isolates along the food chain has to be considered critically.

Occurrence and Characteristics of Mobile Colistin Resistance (mcr) Gene-Containing Isolates from the Environment: A Review.

The emergence and spread of mobile colistin (COL) resistance (mcr) genes jeopardize the efficacy of COL, a last resort antibiotic for treating deadly infections. COL has been used in livestock for decades globally. Bacteria have mobilized mcr genes (mcr-1 to mcr-9). Mcr-gene-containing bacteria (MGCB) have disseminated by horizontal/lateral transfer into diverse ecosystems, including aquatic, soil, botanical, wildlife, animal environment, and public places. The mcr-1, mcr-2, mcr-3, mcr-5, mcr-7, and mcr-8 have been detected in isolates from and/or directly in environmental samples. These genes are harboured by Escherichia coli, Enterobacter, Klebsiella, Proteus, Salmonella, Citrobacter, Pseudomonas, Acinetobacter, Kluyvera, Aeromonas, Providencia, and Raulotella isolates. Different conjugative and non-conjugative plasmids form the backbones for mcr in these isolates, but mcr have also been integrated into the chromosome of some strains. Insertion sequences (IS) (especially ISApl1) located upstream or downstream of mcr, class 1–3 integrons, and transposons are other drivers of mcr in the environment. Genes encoding multi-/extensive-drug resistance and virulence are often co-located with mcr on plasmids in environmental isolates. Transmission of mcr to/among environmental strains is clonally unrestricted. Contact with the mcr-containing reservoirs, consumption of contaminated animal-/plant-based foods or water, international animal-/plant-based food trades and travel, are routes for transmission of MGCB.

Emergence of mobile colistin resistance genes mcr-1 and mcr-8 in Saudi Arabia

Emergence of mobile colistin resistance genes mcr-1 and mcr-8 in Saudi Arabia

The characterization of mobile colistin resistance (mcr) genes among 33 000 Salmonella enterica genomes from routine public health surveillance in England.

To establish the prevalence of mobile colistin resistance (mcr) genes amongst Salmonella enterica isolates obtained through public health surveillance in England (April 2014 to September 2017), 33 205 S . enterica genome sequences obtained from human, food, animal and environmental isolates were screened for the presence of mcr variants 1 to 8. The mcr-positive genomes were assembled, annotated and characterized according to plasmid type. Nanopore sequencing was performed on six selected isolates with putative novel plasmids, and phylogenetic analysis was used to provide an evolutionary context for the most commonly isolated clones. Fifty-two mcr-positive isolates were identified, of which 32 were positive for mcr-1, 19 for mcr-3 and 1 for mcr-5. The combination of Illumina and Nanopore sequencing identified three novel mcr-3 plasmids and one novel mcr-5 plasmid, as well as the presence of chromosomally integrated mcr-1 and mcr-3. Monophasic S. enterica serovar Typhimurium accounted for 27/52 (52 %) of the mcr-positive isolates, with the majority clustering in clades associated with travel to Southeast Asia. Isolates in these clades were associated with a specific plasmid range and an additional extended-spectrum beta-lactamase genotype. Routine whole-genome sequencing for public health surveillance provides an effective screen for novel and emerging antimicrobial determinants, including mcr. Complementary long-read technologies elucidated the genomic context of resistance determinants, offering insights into plasmid dissemination and linkage to other resistance genes.

Identification of novel mobile colistin resistance gene mcr-10

ABSTRACT Mobile colistin resistance (mcr) genes represent an emerging challenge. Here we describe a novel mcr gene, mcr-10, on an IncFIA plasmid of an Enterobacter roggenkampii clinical strain. mcr-10 has the highest nucleotide identity (79.69%) with mcr-9 and encodes MCR-10 with 82.93% amino acids identical to MCR-9. mcr-10 confers 4-fold increase in colistin MIC (from 1 to 4 mg/L) when cloned into a colistin-susceptible E. roggenkampii strain. By screening GenBank, mcr-10 was found in various Enterobacteriaceae species of countries in four continents, suggesting that this gene has widely spread. MCR-10 shows 79.04% to 83.67% amino acid identity and highly conserved predicted protein structures with chromosomally encoded MCR-like phosphoethanolamine transferases (designated MCR-B here) of various Buttiauxella species. MCR-10, MCR-9 and MCR-B proteins may, therefore, originate from a common ancestor. mcr-10 was adjacent to a site-specific recombinase-encoding gene and was bracketed by IS903 and may be mobilized by site-specific recombination or composite transposon. Our results indicate that mcr-10 is a novel plasmid-borne colistin resistance gene and warrants immediate monitoring and further studies.

Prevalence and characteristics of multidrug-resistant mcr-1-positive Escherichia coli isolates from broiler chickens in Tai'an, China

Colibacillosis, caused by Escherichia coli, is one of the most common bacterial diseases of chickens. The high incidence and considerable economic losses associated with colibacillosis make it a significant concern worldwide. In recent years, the efficacy of colistin has been severely impacted by the emergence of plasmid-mediated colistin resistance genes, especially mcr-1. Therefore, monitoring of antibiotic resistance, particularly colistin resistance, amongst E. coli strains is vitally important to the future growth and sustainability of the poultry industry. In this study, a total of 130 E. coli strains were isolated from the livers of chickens displaying symptoms of colibacillosis in Tai'an, China. Isolates were screened for their susceptibility to various antibiotics and for the presence of mobile colistin resistance genes and other antibiotic resistance genes. Overall, 75 (57.7%) isolates showed resistance to colistin and were positive for mcr-1. The mobile colistin resistance genes, mcr-2, -3, and -4, were not detected in this study. Of the 75 mcr-1-positive isolates, all (100%) also carried tetracycline resistance genes, 71 (94.7%) also contained genes associated with β-lactam resistance, 59 (78.7%) contained aminoglycoside resistance genes, and 57 (76%) contained sulfonamide resistance genes. This high prevalence of multidrug resistance among mcr-1-positive E. coli isolates, including the production of extended-spectrum β-lactamases, is highly concerning. The surveillance findings presented here will be conducive to our understanding of the prevalence and characteristics of multidrug-resistance in E. coli in the Tai'an area and will provide a better scientific basis for the clinical treatment of colibacillosis in chickens.

Diverse Escherichia coli lineages from domestic animals carrying colistin resistance gene mcr-1 in an Ecuadorian household

ObjectiveThe aim of this study was to detect potential animal reservoirs of Escherichia coli carrying the mcr-1 gene in an Ecuadorian household. MethodsThe mobile colistin-resistance gene, mcr-1, was first detected in Ecuador in a commensal E. coli isolate from a boy. A cross-sectional study was performed to detect the possible source of colistin-resistant E. coli in the boy’s household. Faecal swabs and soil faecal samples were collected from companion animals. Samples were plated on selective media to isolate colistin-resistant E. coli and isolates were submitted to PCR detection of mcr-1, pulsed field gel electrophoresis (PFGE), and multi-locus sequences typing (MLST). Moreover, the genomes of all the isolates were sequenced. ResultsThree different colistin-resistant E. coli sequence types (ST3941, 1630 and 2170), corresponding to three PFGE patterns, were obtained from a chicken and two dogs; these isolates were different from the human isolate (ST609). By whole-genome sequencing, the mcr-1.1 gene was found on IncI2 plasmids with very high nucleotide identity. ConclusionsOur results indicate a polyclonal dissemination of mcr-1.1 in the environment surrounding the first MCR-producing E. coli strain reported in Ecuador. Our findings support the idea of lateral dissemination of mcr-1.1 gene between unrelated E. coli isolates.

Multidrug-Resistant and Clinically Relevant Gram-Negative Bacteria Are Present in German Surface Waters.

Water is considered to play a role in the dissemination of antibiotic-resistant Gram-negative bacteria including those encoding Extended-spectrum beta-lactamases (ESBL) and carbapenemases. To investigate the role of water for their spread in more detail, we characterized ESBL/Carbapenemase-producing bacteria from surface water and sediment samples using phenotypic and genotypic approaches. ESBL/Carbapenemase-producing isolates were obtained from water/sediment samples. Species and antibiotic resistance were determined. A subset of these isolates (n = 33) was whole-genome-sequenced and analyzed for the presence of antibiotic resistance genes and virulence determinants. Their relatedness to isolates associated with human infections was investigated using multilocus sequence type and cgMLST-based analysis. Eighty-nine percent of the isolates comprised of clinically relevant species. Fifty-eight percent exhibited a multidrug-resistance phenotype. Two isolates harbored the mobile colistin resistance gene mcr-1. One carbapenemase-producing isolate identified as Enterobacter kobei harbored blaVIM–1. Two Escherichia coli isolates had sequence types (ST) associated with human infections (ST131 and ST1485) and a Klebsiella pneumoniae isolate was classified as hypervirulent. A multidrug-resistant (MDR) Pseudomonas aeruginosa isolate encoding known virulence genes associated with severe lung infections in cystic fibrosis patients was also detected. The presence of MDR and clinically relevant isolates in recreational and surface water underlines the role of aquatic environments as both reservoirs and hot spots for MDR bacteria. Future assessment of water quality should include the examination of the multidrug resistance of clinically relevant bacterial species and thus provide an important link regarding the spread of MDR bacteria in a One Health context.

An exploration of the gut and environmental resistome in a community in northern Vietnam in relation to antibiotic use

BackgroundAntibiotic resistance is a major global public health threat. Antibiotic use can directly impact the antibiotic resistant genes (ARGs) profile of the human intestinal microbiome and consequently the environment through shedding.MethodsWe determined the resistome of human feces, animal stools, human food and environmental (rain, well, and irrigative water) samples (n = 304) in 40 households within a community cohort and related the data to antibiotic consumption. Metagenomic DNA was isolated and qPCR was used to determine presence of mobile colistin resistance (mcr) genes, genes encoding extended-spectrum β-lactamases (ESBL), carbapenemases and quinolone resistance genes.ResultsNearly 40 % (39.5%, 120/304) of samples contained ESBL genes (most frequent were CTX-M-9 (23.7% [72/304]), CTX-M-1 (18.8% [57/304]). Quinolone resistance genes (qnrS) were detected in all human and 91% (41/45) of animal stool samples. Mcr-1 and mcr-3 were predominantly detected in human feces at 88% (82/93) and 55% (51/93) and animal feces at 93% (42/45) and 51% (23/45), respectively. Mcr-2, mrc-4 and mcr-5 were not detected in human feces, and only sporadically (< 6%) in other samples. Carbapenemase-encoding genes were most common in water (15% [14/91]) and cooked food (13% [10/75]) samples, while their prevalence in human and animal stools was lower at 4% in both human (4/93) and animal (2/45) samples. We did not find an association between recent antibiotic consumption and ARGs in human stools. Principal component analysis showed that the resistome differs between ecosystems with a strong separation of ARGs profiles of human and animal stools on the one hand versus cooked food and water samples on the other.ConclusionsOur study indicated that ARGs were abundant in human and animal stools in a rural Vietnamese community, including ARGs targeting last resort antibiotics. The resistomes of animal and human stools were similar as opposed to the resistomes from water and food sources. No association between antibiotic use and ARG profiles was found in a setting of high background rates of AMR.

Mobile Colistin Resistance (MCR) Gene, Antimicrobial Resistance: A Global Public Health Threat

Abstract not available&#x0D; Bangladesh Journal of Medical Science Vol.19(1) 2020 p.5-10

An overview of colistin resistance, mobilized colistin resistance genes dissemination, global responses, and the alternatives to colistin: A review

Colistin, also known as polymyxin E, is an antimicrobial agent that is effective against a variety of Gram-negative bacilli, especially the Enterobacteriaceae family. Recently, the wide dissemination of colistin-resistance has brought strong attention to the scientific society because of its importance as the last resort for the treatment of carbapenem-resistant Enterobacteriaceae infections and its possible horizontal transmission. The mobilized colistin resistance (mcr) gene was identified as the gene responsible for unique colistin resistance. Indeed, despite many studies that have revealed a pan variation in the existence of this gene, not only for the mcr genes main group but also for its many subgroups, the problem is growing and worsening day after day. In this regard, this review paper is set to review the updated data that has been published up to the end of 2019 third quarter, especially when related to colistin resistance by the mcr genes. It will include the present status of colistin resistance worldwide, the mcr gene dissemination in different sectors, the discovery of the mcr variants, and the global plan to deal with the threat of antimicrobial resistance. In line with global awareness, and to stop antibiotic misuse and overuse, especially in agricultural animals, the study will further discuss in detail the latest alternatives to colistin use in animals, which may contribute to the elimination of inappropriate antibiotic use and to the help in preventing infections. This review will advance our understanding of colistin resistance, while supporting the efforts toward better stewardship, for the proper usage of antimicrobial drugs in humans, animals, and in the environment.

494. Fitness Cost of mcr-1-Mediated Colistin Resistance in Carbapenemase-Producing Klebsiella pneumoniae

BackgroundThe emergence of mobile colistin resistance gene mcr-1, a plasmid-borne polymyxin resistance mechanism, in carbapenem-resistant Klebsiella pneumoniae is an alarming concern. However, previous studies showed that the acquisition of mcr-1 was associated with a significant biological fitness cost in K. pneumoniae. We aimed to study the impact of mcr-1 on the biological fitness in clinical carbapenemase-producing K. pneumoniae strains.MethodsClinical carbapenemase-producing K. pneumoniae strains were collected consecutively at the Taipei Veterans General Hospital between November 2017 and December 2018. The strain positive for mcr-1 was subjected to whole-genome sequencing to delineate its genomic features. Escherichia coli J53 strain was used as the recipient strain in plasmid conjugation assay and the transconjugants were selected with sodium azide and colistin. Plasmid stability was tested by serial passaging in antibiotic-free LB broth for 28 days. The growth rate was compared between the parental mcr-1-bearing strain and the plasmid-cured strain.ResultsOne ST11 strain isolated from a fatal case with bacteremia (KP2509) was found to harbor blaKPC-2, blaOXA-48, and mcr-1. This strain was resistant to colistin (MIC=8 mg/L) and imipenem (MIC≥16 mg/L). Whole-genome sequencing of KP2509 showed that mcr-1, blaKPC-2 and blaOXA-48 were located on an IncHI-FIB type plasmid of 319 Kb, an IncFII type plasmid of 96 Kb, and an IncL type plasmid of 64 Kb, respectively. Conjugation efficiency of mcr-1-bearing plasmid was 2.24 × 10–4, and the colistin MIC of E. coli J53 transconjugant increased from 0.5 to 8 mg/L. The mcr-1-bearing plasmid in KP2509 showed high plasmid stability, and only ~1% were lost after 27-day passages. The resulting plasmid-cured strain (PC-KP2509) was susceptible to colistin (MIC=0.5 mg/L) and had a similar growth rate to that of parental mcr-1-bearing strain KP2509.ConclusionWe identified an ST11 K. pneumoniae strain carrying blaKPC-2, blaOXA-48, and mcr-1 genes causing a fatal bacteremia. The large mcr-1-bearing plasmid confers a moderate level of colistin resistance but without significant biological fitness cost in carbapenemase-producing K. pneumoniae, which could result in a serious threat clinically.Disclosures All authors: No reported disclosures.

Multiple importations and transmission of colistin-resistant Klebsiella pneumoniae in a hospital in northern India.

Resistance to colistin, a last resort antibiotic, has emerged in India. We investigated colistin-resistant Klebsiella pneumoniae(ColR-KP) in a hospital in India to describe infections, characterize resistance of isolates, compare concordance of detection methods, and identify transmission events. Retrospective observational study. Case-patients were defined as individuals from whom ColR-KP was isolated from a clinical specimen between January 2016 and October 2017. Isolates resistant to colistin by Vitek 2 were confirmed by broth microdilution (BMD). Isolates underwent colistin susceptibility testing by disk diffusion and whole-genome sequencing. Medical records were reviewed. Of 846 K. pneumoniae isolates, 34 (4%) were colistin resistant. In total, 22 case-patients were identified. Most (90%) were male; their median age was 33 years. Half were transferred from another hospital; 45% died. Case-patients were admitted for a median of 14 days before detection of ColR-KP. Also, 7 case-patients (32%) received colistin before detection of ColR-KP. All isolates were resistant to carbapenems and susceptible to tigecycline. Isolates resistant to colistin by Vitek 2 were also resistant by BMD; 2 ColR-KP isolates were resistant by disk diffusion. Moreover, 8 multilocus sequence types were identified. Isolates were negative for mobile colistin resistance (mcr) genes. Based on sequencing analysis, in-hospital transmission may have occurred with 8 case-patients (38%). Multiple infections caused by highly resistant, mcr-negative ColR-KP with substantial mortality were identified. Disk diffusion correlated poorly with Vitek 2 and BMD for detection of ColR-KP. Sequencing indicated multiple importation and in-hospital transmission events. Enhanced detection for ColR-KP may be warranted in India.

Multiple Cross Displacement Amplification Coupled With Gold Nanoparticles-Based Lateral Flow Biosensor for Detection of the Mobilized Colistin Resistance Gene mcr-1.

Fast dissemination of the mobilized colistin resistance (mcr) gene mcr-1 in Enterobacteriaceae causes a huge threat to the treatment of severe infection. In the current report, a multiple cross displacement amplification (MCDA) coupled with the detection of amplified products by gold nanoparticles-based lateral flow biosensor (LFB) assay (MCDA-LFB) was established to identify the mcr-1 gene with simpleness, rapidity, specificity, and sensitivity. The MCDA-LFB assay was performed at a isothermal temperature (63°C) for only 30 min during the amplification stage, and the reaction products were directly identified by using LFB which obtained the result within 2 min. The entire process of experiments, from templates extraction to result judging, was accomplished in <60 min. For the analytical specificity of this method, all of the 16 mcr-1-producing strains were positive, and all of the non-mcr-1 isolates produced the negative results. The sensitivity of mcr-1-MCDA-LFB assay was as little as 600 fg of plasmid DNA per reaction in pure culture, and approximately 4.5 × 103 CFU/mL (~4.5 CFU/reaction) in spiked fecal samples. Therefore, this technique established in the present study is suitable for the surveillance of mcr-1 gene in clinic and livestock industry.

Integrated aquaculture contributes to the transfer of mcr-1 between animals and humans via the aquaculture supply chain

BackgroundSince its discovery in 2015, the mobile colistin resistance gene mcr-1 has been reported in bacteria from >50 countries. Although aquaculture-associated bacteria may act as a significant reservoir for colistin resistance, systematic investigations of mcr-1 in the aquaculture supply chain are scarce. ObjectivesWe investigated the presence of colistin resistance determinants in the aquaculture supply chain in south China and determined their characteristics and relationships. MethodsA total of 250 samples were collected from a duck-fish integrated fishery, slaughter house, and market in Guangdong Province, China, in July 2017. Colistin-resistant bacteria were isolated on colistin-supplemented CHROMagar Orientation plates, and the species were identified by matrix-assisted laser desorption/ionization time-of-flight assay. The presence of mcr genes was confirmed by polymerase chain reaction analysis. We examined the minimum inhibitory concentrations (MICs) of 16 antimicrobial agents against the isolates using agar diffusion and broth microdilution methods. Whole-genome sequencing (WGS) was used to explore the molecular characteristics and relationships of mcr-1-positive Escherichia coli (MCRPEC). ResultsOverall, 143 (57.2%) colistin-resistant bacteria were isolated, of which, 56 (22.4%, including 54 Escherichia coli and two Klebsiella pneumoniae) and four Aeromonas species were positive for mcr-1 and mcr-3, respectively. The animal-derived MCRPEC were significantly more prevalent in integrated fishery samples (40.0%) than those in market (4.8%, P<0.01) samples but not in slaughter house (28.0%, P=0.164). All MCRPEC were highly resistant to ampicillin, tetracycline, and compound sulfamethoxazole (>90%) but were susceptible to carbapenems and tigecycline. WGS analysis suggested that mcr-1 was mainly contained on plasmids, including IncHI2 (29.6%), IncI2 (27.8%), IncX4 (14.8%), and IncP (11.1%). Genomic analysis suggested mcr-1 transmission via the aquatic food chain. ConclusionsMCRPEC were highly prevalent in the aquaculture supply chain, with the isolates showing resistance to most antibiotics. The data suggested mcr-1 could be transferred to humans via the aquatic food chain. Taking the “One Health” perspective, aquaculture should be incorporated into systematic surveillance programs with animal, human, and environmental monitoring.

Emergence of Colistin Resistance Gene mcr-8 and Its Variant in Raoultella ornithinolytica.

Recently, a novel mobile colistin resistance gene, mcr-8, was identified in Klebsiella pneumoniae. Here, we report the identification of mcr-8 and its variant, mcr-8.4, in Raoultella ornithinolytica isolates which also belong to Enterobacteriaceae family. The mcr-8 gene was located on transferrable plasmids with difference sizes. Notably, the transferability of mcr-8-carrying plasmids was enhanced once they entered into Escherichia coli hosts and multiple β-lactamase genes could co-transfer with mcr-8. These findings expand our knowledge of mcr-8-carrying bacterial species.

Plasmid-mediated colistin resistance gene mcr-1 in Escherichia coli and Klebsiella pneumoniae isolated from market retail fruits in Guangzhou, China.

BackgroundAs a result of the growing prevalence of the plasmid-mediated mobile colistin resistance gene mcr-1 among Gram-negative bacteria, the surveillance of mcr-1 has been globally applied. In our study, we aimed to shed light on the possibility of transmission of mcr-1-resistant isolates through market retail fruits.Methods and resultsHerein, 133 different fruit surface samples were collected and screened for the different MCR variants (mcr-1 to mcr-8) using PCR and confirmed with sequencing. We identify for the first time mcr-1-carrying Escherichia coli and Klebsiella pneumoniae from market retail fruits in Guangzhou, China. Minimum inhibitory concentrations were detected by the broth microdilution method. Liquid mating was performed to check the transferability of the mcr-1 gene. Pulsed field gel electrophoresis analysis of S1 nuclease-digested DNA and Southern blotting were performed to check the location of the mcr-1 gene. Then, whole-genome sequencing and in silico multilocus sequence typing analysis were performed.ConclusionWe showed that E. coli GB110 can mediate the spreading of antibiotic resistance genes through the food chain, while K. pneumoniae GB015 was considered to be the progenitor of the most successful multidrug-resistant clone. Since fruits are usually consumed fresh, this may serve as a direct source of mcr-1-producing bacteria in humans that requires prompt surveillance and intervention to limit the spread of resistance.