Mcr-1 Gene Research Articles

Thymus algeriensis essential oil: Phytochemical investigation, bactericidal activity, synergistic effect with colistin, molecular docking, and dynamics analysis against Gram-negative bacteria resistant to colistin

Due to the increasing resistance prevalence to the last line of antibiotics, such as colistin, and the rising threat of multi-drug resistant bacteria, it is crucial to find alternative therapeutic options. The current study focuses on evaluating antibacterial activities alone and in combination with colistin of Thymus algeriensis essential oil (TA-EO) against colistin-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli co-harboring mcr-1 gene. GC/MS was used to determine the chemical composition of TA-EO. Disc diffusion and microdilution techniques were used to evaluate the antimicrobial activities of TA-EO. Synergism between colistin and TA-EO was evaluated by checkerboard assay. The major compounds of TA-EO were docked with known enzymes involved in resistance to colistin, as well as the biosynthesis of peptidoglycan and amino acids. GC/MS revealed that TA-EO was of carvacrol chemotype (67.94 %). The TA-EO showed remarkable antibacterial activities against all Gram-negative bacterial strains, with the diameter of inhibition zones varied between 30 and 50 mm and a ratio MBC/MIC equal to 1 for the vast majority of bacterial isolates. Interestingly, the checkerboard showed synergism between TA-EO and colistin against colistin-resistant Escherichia coli co-harboring mcr-1 gene (FICI˂1) and reduced the MIC of colistin by 16- to 512-fold and those of TA-EO by 4- to 16-fold. The docking study demonstrated that carvacrol had high binding free energies against MCR-1, a phosphoethanolamine transferase extracellular domain, and its catalytic domain implicated in resistance to colistin, and undecaprenyl pyrophosphate synthase in complex with magnesium which is involved in bacterial peptidoglycan biosynthesis. The molecular dynamics study for 100-ns also revealed the stability of the MCR-1/carvacrol complex with a constant surface area over the simulation. These results support using carvacrol or TA-EO as a bactericidal agent, either alone or in combination with colistin, to treat infections caused by colistin-resistant Gram-negative bacteria.

Detection of PhoP-mediated Colistin Resistance in Gram-negative bacteria without mcr genes in Water in the Ho Municipality, Ghana

Detection of PhoP-mediated Colistin Resistance in Gram-negative bacteria without mcr genes in Water in the Ho Municipality, Ghana

Decoding the origins, spread, and global risks of mcr-9 gene

The global spread of the plasmid-mediated mcr (mobilized colistin resistance) gene family presents a significant threat to the efficacy of colistin, a last-line defense against numerous Gram-negative pathogens. The mcr-9 is the second most prevalent variant after mcr-1. A dataset of 698 mcr-9-positive isolates from 44 countries is compiled. The historical trajectory of the mcr-9 gene is reconstructed using Bayesian analysis. The effective reproduction number is used innovatively to study the transmission dynamics of this mobile-drug-resistant gene. Our investigation traces the origins of mcr-9 back to the 1960s, revealing a subsequent expansion from Western Europe to the America and East Asia in the late 20th century. Currently, its transmissibility remains high in Western Europe. Intriguingly, mcr-9 likely emerged from human-associated Salmonella and exhibits a unique propensity for transmission within the Enterobacter. Our research provides a new perspective that this host preference may be driven by codon usage biases in plasmids. Specifically, mcr-9-carrying plasmids prefer the nucleotide C over T compared to mcr-1-carrying plasmids among synonymous codons. The same bias is seen in Enterobacter compared to Escherichia (respectively as their most dominant genus). Furthermore, we uncovered fascinating patterns of coexistence between different mcr-9 subtypes and other resistance genes. Characterized by its low colistin resistance, mcr-9 has used this seemingly benign feature to silently circumnavigate the globe, evading conventional detection methods. However, colistin-resistant Enterobacter strains with high mcr-9 expression have emerged clinically, implying a strong risk of mcr-9 evolving into a global "true-resistance-gene". This study explores the mcr-9 gene, emphasizing its origin, adaptability, and dissemination potential. Given the high mcr-9 expression colistin-resistant strains was observed in clinically the prevalence of mcr-9 poses a significant challenge to drug resistance prevention and control within the One Health framework. This work was partially supported by the National Natural Science Foundation of China (Grant No. 32141001 and 81991533).

Emergence of multidrug resistant mobile colistin resistance (mcr) carrying Aeromonas spp. isolated from retail foods in Mymensingh district, Bangladesh

The emergence of plasmid-mediated mobile colistin resistance (mar) in bacteria under Enterobacteriaceae, and aeromonads isolated from foods has been reported in many parts of the world. So far, we know there is no report of mcr carrying Aeromonas spp. Isolated from retail foods in Bangladesh. Therefore, this study was carried out to determine the prevalence of mcr carrying Aeromonas spp. isolated from retail foods (meat, milk, and fish) in Mymensingh district and their characterization for antimicrobial resistance patterns. The prevalence of mcr-1 gene carrying Aeromonas spp. was 30 % (15/50) in chickens, 23 % (8/35) in fish, and 10 % (2/20) in milk. No other tested mcr gene variants (mcr-2 to 4) were detected. The minimum inhibitory concentration (MIC) for colistin was determined to be 80% (12/15) and 75% (6/8) of the mcr-1 gene carrying Aeromonas spp. isolated from chicken and fish, respectively, had an MIC of 8-16 µg/ml whereas 100% (2/2) of the isolate from milk showed a MIC of 4–8 µg/ml. Most of the mcr-1 gene-carrying isolates from chicken meats, fish, and milk were resistant to oxytetracycline, and ampicillin (80%–100%). Apart from multidrug resistant (MDR), extensive MDR was detected in mcr-1 gene-carrying Aeromonas spp., irrespective of the sample’s origin. Overall, these data suggested that the mcr-1 gene-carrying Aeromonas spp. in retail foods could be a potential reservoir for antimicrobial resistance determinants. To the best of our knowledge, this is the first report of the mcr gene carrying Aeromonas spp. isolated from retail foods such as chicken meat, fish, and milk in Bangladesh. Res. Agric. Livest. Fish. Vol. 11, No. 2, August 2024: 115-124

High-throughput screening identification of apigenin that reverses the colistin resistance of mcr-1-positive pathogens.

The plasmid-mediated gene mcr-1 that makes bacteria resistant to the antibiotic colistin is spreading quickly, which means that colistin is no longer working well to treat Gram-negative bacterial infections. Herein, we utilized a computer-aided high-throughput screening drugs method to identify the natural product apigenin, a potential mcr-protein inhibitor, which effectively enhanced the antimicrobial activity of colistin. Several assays, including a checkerboard minimum inhibitory concentration assay, a time-kill assay, the combined disk test, molecular simulation dynamics, and animal infection models assay, were conducted to verify whether apigenin enhanced the ability of colistin to fight Gram-negative bacterial infections. The results showed that apigenin improved the antimicrobial activity of colistin against multidrug-resistant Enterobacteriaceae infection. Moreover, apigenin not only did not increase the toxic effect of colistin but also had the ability to effectively inhibit the frequency of bacterial resistance mutations to colistin. Studies clearly elucidated that apigenin could interfere with the thermal stability of the protein by binding to the mcr-1 protein. Additionally, the combination of apigenin and colistin could exert multiple effects, including disrupting bacterial membranes, the generation of bacterial nitric oxide and reactive oxygen species, as well as inhibiting bacterial adenosine triphosphate production. Furthermore, the addition of apigenin was able to significantly inhibit colistin-stimulated high expression levels of the bacterial mcr-1 gene. Finally, apigenin exhibited a characteristic anti-inflammatory effect while enhancing the antimicrobial activity of colistin against mcr-1-positive Escherichia coli (E. coli) infected animals. In conclusion, as a potential lead compound, apigenin is promising in combination with colistin in the future treatment of mcr-1-positive E. coli infections.IMPORTANCEThis study found that apigenin was able to inhibit the activity of the mcr-1 protein using a high-throughput virtual screening method. Apigenin effectively enhanced the antimicrobial activity of colistin against multidrug-resistant Enterobacteriaceae, including mcr-1-positive strains, in vitro and in vivo. This study will provide new options and strategies for the future treatment of multidrug-resistant pathogen infections.

Genomic insights into epidemic plasmids carrying bla CTX-M and mcr-1 genes in Escherichia coli from Lebanese broiler production.

In a previous nationwide survey in the Lebanese broiler production, multidrug-resistant CTX-M-producing E. coli were found to carry the mobile colistin resistance gene mcr-1. To investigate the mobile genetic supports responsible for the spread of these resistance genes among E. coli in healthy broilers in Lebanon. Thirty-three bla CTX-M and mcr-1 positive E. coli of various sequence types from 17 broilers farms were subjected to conjugation assays. Long-read sequencing (Oxford Nanopore Technologies) and hybrid assembly were performed to determine complete plasmid sequences and their phylogenetic diversity. Twenty-nine conjugative IncFII plasmids harboured the extended-spectrum β-lactamase genes bla CTX-M-3 (n = 25) or bla CTX-M-55 (n = 4). Highly related IncF2:A-:B-/bla CTX-M-3 plasmids differing only through IS-mediated genetic rearrangements in antibiotic resistance gene clusters were found in genetically diverse E. coli strains isolated from distant farms. The mobile colistin resistance genes mcr-1.1 and mcr-1.26 were carried by IncX4 and IncI2 plasmids. Worryingly, in one isolate, the ISEcp1-bla CTX-M-55 transposable unit was found integrated in a mcr-1.26-carrying IncX4 plasmid. Beside expanded cephalosporins and colistin resistances, all E. coli isolates were multidrug-resistant with different additional resistances against aminoglycosides, (fluoro)quinolones, fosfomycin, phenicols, sulphonamides, tetracycline and trimethoprim. Closely related blaCTX-M-3/55-borne IncF2:A-:B- plasmids harbouring variable MDR regions and mcr-1 carrying IncX4 plasmids are widely disseminated in the E. coli population of healthy broilers in Lebanon. Further surveillance programmes of antimicrobial resistance and interventions to reduce the abusive use of medically important antibiotics are necessary to limit the spread of resistances in food-producing animals in Lebanon.

Sheep and goats as reservoirs of colistin-resistant E. coli: first detection of ETEC ST10 and E. coli ST6396 mcr-1 positive strains in North Africa.

This study aimed to screen and characterize colistin-resistant strains isolated from different livestock species in Algeria, including sheep, goats, and dromedaries. A total of 197 rectal and nasal swabs were screened for colistin-resistant Gram-negative bacilli. Twenty one isolates were selected, identified, and their antibiotic resistance was phenotypically and genotypically characterized. The majority (15/21) were affiliated to Escherichia coli, from which 4 strains isolated from sheep (n=2) and goats (n=2) and belonging to phylogroup A and ST10 and ST6396 lineages, respectively, carried the mcr-1 gene. The remaining isolates were identified as belonging to the following genera: Raoultella, Enterobacter, Klebsiella, and Pseudomonas. This study highlights the presence of virulent and multiresistant Gram-negative bacilli in farm animals, increasing the risk of transmitting potentially fatal infections to humans.

Molecular Epidemiology of mcr-1-Positive Polymyxin B-Resistant Escherichia coli Producing Extended-Spectrum β-Lactamase (ESBL) in a Tertiary Hospital in Shandong, China.

Escherichia coli, a rod-shaped Gram-negative bacterium, is a significant causative agent of severe clinical bacterial infections. This study aimed to analyze the epidemiology of extended-spectrum β-lactamase (ESBL)-producing mcr-1 -positive E. coli in Shandong, China. We collected 668 non-duplicate ESBL-producing E. coli strains from clinical samples at Shandong Provincial Hospital between January and December 2018, and estimated their minimum inhibitory concentrations (MICs) using a VITEK® 2 compact system and broth microdilution. Next-generation sequencing and bioinformatic analyses identified the mcr-1 gene and other resistance genes in the polymyxin B-resistant strains. The conjugation experiment assessed the horizontal transfer capacity of the mcr-1 gene. Of the strains collected, 24 polymyxin B-resistant strains were isolated with a positivity rate of 3.59% and among the 668 strains, 19 clinical strains carried the mobile colistin resistance gene mcr-1, with a positivity rate of approximately 2.8%. All 19 clinical strains were resistant to ampicillin, cefazolin, ceftriaxone, ciprofloxacin, levofloxacin, and polymyxin B. Seventeen strains successfully transferred the mcr-1 gene into E. coli J53. All transconjugants were resistant to polymyxin B, and carried the drug resistance gene mcr-1. The 19 clinical strains had 14 sequence types (STs), with ST155 (n = 4) being the most common. The whole-genome sequencing results of pECO-POL-29_mcr1 revealed that no ISApl1 insertion sequences were found on either side of the mcr-1 gene. Our study uncovered the molecular epidemiology of mcr-1-carrying ESBL-producing E. coli in the region and suggested horizontal transmission mediated by plasmids as the main mode of mcr-1 transmission.

Prevalence and Molecular Characterization of Carbapenem and Colistin-Resistance Genes in Clinical Strains of Pseudomonas aeruginosa Isolated from Diabetic Patients

Abstract Introduction Pseudomonas aeruginosa is one of the important opportunistic nosocomial pathogens that are increasingly becoming resistant to many drugs including the drugs of last resort, carbapenems, and colistin. Methods The study involved the examination of clinical isolates of P. aeruginosa recovered from diabetic patients for the presence of acquired genes implied in carbapenem and colistin resistance. Results A total of 100 clinical isolates from diabetic patients' wound and sputum were investigated for their susceptibility to imipenem and colistin followed by phenotypic assay and resistance gene screening. The study revealed 27 sputum isolates being resistant to imipenem further confirmed by a modified Hodge test and 28 wound isolates were resistant to colistin. The resistant isolates of wound and sputum were found to possess blaOXA-48 , blaVIM , mcr-1, and mcr-5 genes. The strains had a coexistence of carbapenem- and colistin-resistant genes. Conclusion Considering the fact that infection by such resistant isolates in diabetics could be frightening, clinical laboratories must employ rapid diagnostic methods to detect resistance which can aid in the treatment decision-making.

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.

Carbapenems and colistin resistance genes isolated in Musca domestica from a garbage dump near a hospital in Lima.

Motivation for the study. The presence of antibiotic resistance genes in bacteria isolated from common flies is a potential public health hazard because it facilitates the presence and spread of antibiotic resistance genes in the environment. Main findings. Thirty-eight bacterial strains identified in 14 species were isolated from within the fly bodies, of which 31 strains showed resistance to carbapenems and 26 strains showed resistance to colistin. Seven bacterial strains showed carbapenem resistance genes and one Escherichia coli strain had resistance to KPC, OXA-48 and mcr-1. Implications. This is the first report of antibiotic resistance genes in bacteria carried by common flies in Peru. The objective was to determine the presence of carbapenem resistance genes and plasmid resistance to colistin (mcr-1) in bacteria isolated from Musca domestica in a garbage dump near a hospital in Lima, Peru. Bacteria with phenotypic resistance to carbapenemics were isolated on CHROMagar mSuperCARBATM medium and colistin resistance profiling was performed using the colistin disk elution method. Detection of blaKPC, blaNDM, blaIMP, blaOXA-48, blaVIM and mcr-1 genes was performed by conventional PCR. The antimicrobial susceptibility profile was determined using the automated MicroScan system. We found that 31/38 strains had phenotypic resistance to carbapenemics and 26/38 strains had phenotypic resistance to colistin with a minimum inhibitory concentration ≥ 4 µg/ml. Finally, we identified seven bacterial strains with carbapenem resistance genes (OXA-48 and KPC) and one bacterial strain with plasmid resistance to colistin (mcr-1). One Escherichia coli strain had three resistance genes: KPC, OXA-48 and mcr-1.

Metallo-β-lactamases producing Pseudomonas aeruginosa and the molecular mechanism of drug resistance variants

BackgroundMetallo-β-lactamases (MBLs) type carbapenemases are produced by pathogenic Pseudomonas spp. and exhibit carbapenemase activity. The study will look into drug resistance and the molecular mechanisms of drug-resistant Pseudomonas aeruginosa variants. MethodsA total of 74 P. aeruginosa strains were isolated from urine, pus, sputum, blood, throat swab, Foley’s catheter, and nasal swab. The isolates were screened for antibiotic susceptibility and the identified MDR strains were further tested for β-lactamase production. Multiplex PCR was used to identify the presence of mcr-1 and blaNDM-1 genes in MDR organisms. The minimum inhibitory concentration for ceftazidime and colistin was also determined, in addition to the biofilm inhibitor activity. Confocal microscopy was used to determine the production of biofilms. ResultsThe isolated P. aeruginosa strains exhibited antibiotic resistance to aminoglycosides (amikacin and gentamicin). Fifty three percent of the isolated P. aeruginosa strains produced metallo-β-lactamase and the remaining isolates were non-metallo-β-lactamase type (46.8 %) (p < 0.0001). The MIC value of β-lactamase producers against colistin ranges from 0.5 µg/mL to 6 µg/mL. The MDR bacteria exhibited mcr-1 and blaNDM−1 genes. The MDR P. aeruginosa strain treated with colistin and ceftazidime inhibited initial biofilm formation. These combination of antibiotics effectively prevented initial biofilm development than individual antibiotics (p < 0.001). ConclusionsThe current analysis detected MDR among P. aeruginosa isolates that carried drug-resistant genes.

Evaluation and Molecular Characterization of Colistin-Resistant Isolates of Pseudomonas aeruginosa and Klebsiella pneumoniae from the Infected Wounds of Hospitalized Patients.

This study was planned to determine the colistin-resistant (CR) gene distribution among two species of gram-negative bacteria, Pseudomonas aeruginosa and Klebsiella pneumoniae. In total, 50 isolates of K. pneumoniae (14 isolates, 28%) and P. aeruginosa (36 isolates, 72%) were isolated between August 2023 and October 2023 from clinical wound samples at Jinnah Hospital and Lahore General Hospital Lahore, Pakistan. To determine the resistance genes linked to CR and assess antimicrobial susceptibility, all isolates were kept at -80°C in 15% glycerol broth. Using the right primer sets, a polymerase chain reaction (PCR) was utilized to identify the CR-associated mcr-1 gene of the gramnegative isolates. Out of 50, 40 isolates (80%) showed resistance against colistin with MICs of 8 and 128 μg/ml. The majority (97%) of P. aeruginosa CR strains were considered multidrug resistant (MDR). All K. pneumoniae isolates were resistant to cefepime, cotrimoxazole, ceftriaxone, and imipenem. The clinical CR isolates of P. aeruginosa were highly resistant to ceftriaxone, imipenem, cefepime, cotrimoxazole, ciprofloxacin, amikacin, and piperacillin/tazobactum. The antibiotic resistance pattern was terrifyingly high among both bacterial species. According to the PCR results, CR was prevalent among the gram-negative samples, and the mcr-1 gene was positive in 6/40 (15%) of the CR isolates, including four P. aeruginosa and two K. pneumoniae strains. The high CR (80%) reported in this research is cause for concern and underscores an urgent need to use colistin in a limited and logical manner, similar to other antibiotics.

Global Variation in Escherichia coli mcr-1 Genes and Plasmids from Animal and Human Genomes Following Colistin Usage Restrictions in Livestock.

Antimicrobial resistance (AMR) is a significant global health threat, with multidrug-resistant (MDR) bacterial clones becoming a major concern. Polymyxins, especially colistin, have reemerged as last-resort treatments for MDR Gram-negative infections. However, colistin use in livestock has spread mobile colistin resistance (mcr) genes, notably mcr-1, impacting human health. In consequence, its livestock use was banned in 2017, originating a natural experiment to study bacterial adaptation. The aim of this work was to analyse the changes in the mcr-1 genetic background after colistin restriction across the world. This study analyses 3163 Escherichia coli genomes with the mcr-1 gene from human and livestock hosts, mainly from Asia (n = 2621) and Europe (n = 359). Genetic characterisation identifies IncI2 (40.4%), IncX4 (26.7%), and multidrug-resistant IncHI2 (18.8%) as the most common plasmids carrying mcr-1. There were differences in plasmids between continents, with IncX4 (56.6%) being the most common in Europe, while IncI2 (44.8%) was predominant in Asia. Promoter variants related to reduced fitness costs and ISApl1 showed a distinct pattern of association that appears to be associated with adaptation to colistin restriction, which differed between continents. Thus, after the colistin ban, Europe saw a shift to specialised mcr-1 plasmids as IncX4, while ISApl1 decreased in Asia due to changes in the prevalence of the distinct promoter variants. These analyses illustrate the evolution of mcr-1 adaptation following colistin use restrictions and the need for region-specific strategies against AMR following colistin restrictions.

Waterborne polyurethane nanoparticles incorporating linoleic acid as a potential strategy for controlling antibiotic resistance spread in the mammalian intestine

Plasmid-mediated conjugative transfer of antibiotic resistance genes (ARGs) within the human and animal intestine represents a substantial global health concern. linoleic acid (LA) has shown promise in inhibiting conjugation in vitro, but its in vivo effectiveness in the mammalian intestinal tract is constrained by challenges in efficiently reaching the target site. Recent advancements have led to the development of waterborne polyurethane nanoparticles for improved drug delivery. In this study, we synthesized four waterborne polyurethane nanoparticles incorporating LA (WPU@LA) using primary raw materials, including N-methyldiethanolamine, 2,2'-(piperazine-1,4-diyl) diethanol, isophorone diisocyanate, castor oil, and acetic acid. These nanoparticles, identified as WPU0.89@LA, WPU0.99@LA, WPU1.09@LA, and WPU1.19@LA, underwent assessment for their pH-responsive release property and biocompatibility. Among these, WPU0.99@LA displayed superior pH-responsive release properties and biocompatibility towards Caco-2 and IPEC-J2 cells. In a mouse model, a dosage of 10 mg/kg/day WPU0.99@LA effectively reduced the conjugation of IncX4 plasmids carrying the mobile colistin resistance gene (mcr-1) by more than 45.1-fold. In vivo toxicity assessment demonstrated that 10 mg/kg/day WPU0.99@LA maintains desirable biosafety and effectively preserves gut microbiota homeostasis. In conclusion, our study provides crucial proof-of-concept support, demonstrating that WPU0.99@LA holds significant potential in controlling the spread of antibiotic resistance within the mammalian intestine.

Research note: characteristics of blaNDM and mcr-1 co-producing Escherichia coli from retail chicken meat

Carbapenems and colistin are vital antimicrobials used to treat Enterobacteriaceae-caused infections. The present study aimed to characterize the coexistence mechanism of carbapenem and colistin resistance in an Escherichia coli isolated from retail chicken meat. A total of 4 E. coli isolates co-harboring carbapenem resistance gene blaNDM (2 E. coli isolates with blaNDM-5 and 2 with blaNDM-9) and colistin resistance gene mcr-1. Antimicrobial susceptibility testing exhibited that all the 4 E. coli strains had multidrug resistance profile and consistent with the resistance genes they carried. MLST showed that 3 E. coli isolates belonged to a pathogenic E. coli lineage ST354, which is closely associated with human infections and pose a serious threat to public health. Whole genome sequencing (WGS) showed that 4 mcr-1-positive plasmids with sizes of 60.4 kb-67.4 kb all belonged to the IncI2 type. A total of 5 blaNDM-harboring plasmids ranged from 99.0 kb∼138.3 kb, among which 4 plasmids belonged to unknow type and only pCS5L-NDM belonged to IncFIA/IncFIB group of hybrid plasmids, a novel carrier for blaNDM. Comparative analysis exhibited that the mcr-1 or blaNDM-carrying plasmids of E. coli strains from chicken meat showed high identity with that from Enterobacteriaceae of human origin, which indicated the risk of mcr-1 or blaNDM dissemination from retail meat to human. The simultaneous occurrence of mcr-1 and blaNDM in E. coli emphasizes the significant of antimicrobial resistance surveillance in retail meat.

The Occurrence of Colistin Resistance in Potential Lactic Acid Bacteria of Food-Producing Animals in India.

The overuse of colistin, the last-resort antibiotic, has led to the emergence of colistin-resistant bacteria, which is a major concern. Lactic acid bacteria which are generally regarded as safe are known to be reservoirs of antibiotic resistance that possibly pose a threat to human and animal health. Therefore, this study assessed the prevalence of colistin antimicrobial resistance in livestock in India, that is lactic acid bacteria in healthy chickens, sheep, beef, and swine of Mysore. Diverse phenotypic and genotypic colistin resistance were examined among the lactic acid bacterial species (n = 84) isolated from chicken (n = 44), sheep (n = 16), beef (n = 14), and swine (n = 10). Hi-comb, double-disk diffusion tests, Minimum Inhibitory Concentration (MIC), and biofilm formation were assessed for phenotypic colistin resistance. Specific primers for colistin-resistant genes were used for the determination of genotypic colistin resistance. Around 20%, 18%, and 1% were colistin-resistant Lactobacillus, Enterococcus, and Pediococcus species, respectively. Among these, 66.67% exhibited MDR phenotypes, including colistin antibiotic. The identified resistant isolates are Levilactobacillus brevis LBA and LBB (2), Limosilactobacillus fermentum LBF (1), and Pediococcus acidilactici CHBI (1). The mcr-1 and mcr-3 genes were detected in Levilactobacillus brevis LBA, LBB, and Pediococcus acidilactici CHBI isolated from chicken and sheep intestines respectively. The study identified colistin resistance determinants in lactobacilli from food animals, emphasizing the need for enhanced surveillance and monitoring of resistance spread. These findings underscore colistin resistance as a significant medical concern and should be integrated into India's ongoing antimicrobial resistance monitoring programs.

MOLECULAR ANALYSIS OF THE MCR-1 GENE IN PSEUDOMONAS AERUGINOSA AND ACINETOBACTER BAUMANII STRAINS

Objective: The emergence of antibiotic resistance in Pseudomonas aeruginosa and Acinetobacter baumanii isolates poses serious risks to public health. Our study aimed to investigate the presence of colistin resistance and mcr-1 gene positivity in these isolates. Material and Method: Culture, biochemical tests, antibiotic susceptibility tests, and molecular tests were used to isolate and identify P. aeruginosa and A. baumanii strains. Result and Discussion: A sum of 156 clinical isolates of Pseudomonas aeruginosa (n = 89) and Acinetobacter baumannii (n = 67) were obtained using the 550 clinical samples collected in one year from the largest hospital in Van, Turkey. The results of antibiotic susceptibility tests showed that approximately 82.8% of P. aeruginosa and 94.6% of A. baumannii strains were multidrug-resistant (MDR). Colistin resistance was detected in 11.23% (10/89) of P. aeruginosa isolates and 11.94% (8/67) of A. baumannii isolates using agar dilution and microdilution methods. Out of the 18 colistin-resistant isolates, the mcr-1 gene was detected in three P. aeruginosa and two A. baumannii strains. The detection of plasmid-mediated colistin resistance in P. aeruginosa and A. baumannii is of great concern due to the high potential for colistin resistance to spread in clinical settings. Understanding the unique circumstances of worldwide colistin resistance can be facilitated by promoting the creation of quick processes for identifying colistin resistance profiles and putting them into practice in hospital laboratories. Colistin and carbapenem treatment are two effective ways to treat emerging resistant super-microbes and slow down the emergence of resistance.

High prevalence and transmission of blaNDM-positive Escherichia coli between farmed ducks and slaughtered meats: An increasing threat to food safety

The emergence of carbapenem-resistant bacteria especially carbapenem-resistant Escherichia coli (CREC) in food animals poses a serious threat to food safety and public health. Reports about the dissemination of carbapenem-resistant bacteria along the food animal production chain are scattered and mainly focus on swine and chicken. Abuse of antibiotics in duck farms is common especially in China which has the largest duck production industry, however, the CREC transmission between farmed ducks and slaughtered meats remains unclear and the role of slaughterhouse in disseminating CREC among duck meats remains largely unknown. Herein, we collected 251 fecal samples from five typical duck farms along with 125 slaughtered meat samples (25 from each farm) in the corresponding slaughterhouse in Anhui Province, China, in December 2018. All samples were screened for CREC isolates which were analyzed for the presence of carbapenemase genes and colistin resistance gene mcr. The resistance profiles, transferability, pulsed-field gel electrophoresis (PFGE), whole-genome sequencing and phylogenetic analysis of the CREC isolates from both ducks and meats were further characterized. This is the first report presenting the high prevalence of blaNDM-positive CREC isolates in ducks from duck farms (57.8 %) and slaughtered meats (33.6 %) in the corresponding slaughterhouse. Among the 203 blaNDM-positive CREC isolates obtained in this study, 19.2 % harbored mcr-1 and all CREC isolates showed resistance to nearly all currently available antibiotics (except tigecycline). Of note, mcr-1 was found in 17.8 % of the meat-derived CREC carrying blaNDM. Based on the PFGE analysis, clonal spread of blaNDM-positive CREC including some also carrying mcr-1 was found between farmed ducks and slaughtered duck meats even from different farms. Special attention should be paid to the clonal dissemination of meat-derived CREC within the slaughterhouse, which contributed to the high prevalence of blaNDM in slaughtered meats. Additionally, horizontal transmission mainly mediated by transferable blaNDM-5-bearing IncX3 plasmids, untypable blaNDM-1-bearing plasmids and mcr-1-bearing IncHI2 plasmids further facilitated the rapid spread of such multidrug-resistant strains. Notably, the blaNDM-bearing plasmids and mcr-1-bearing plasmids in CREC from meats were highly similar to those from animals and humans. More worryingly, the phylogenomic analysis showed that CREC isolates from both ducks and corresponding meats clustered with previously reported human CREC isolates carrying mcr-1 in different geographical areas including China. These findings further prove that the CREC and resistance plasmids in farmed ducks could transmit to meats even from different farms via the slaughterhouse and then trigger infections in humans. The high prevalence and clonal transmission of CREC isolates including those also carrying mcr-1 between ducks and meats are alarming, and urgent control measures are required to reduce the dissemination of such organisms.

Co-existence of two plasmids harboring transferable resistance-nodulation-division pump gene cluster, tmexCD1-toprJ1, and colistin resistance gene mcr-8 in Klebsiella pneumoniae

BackgroundThe emergence of plasmid-mediated mobile colistin resistance (mcr) gene poses a great challenge to the clinical application of polymyxins. To date, mcr-1 to mcr-10 have been found in animals, humans, and the environment. Among them, mcr-8 was first identified in Klebsiella pneumoniae (K. pneumoniae) of swine origin, and then mcr-8.1 to mcr-8.5 were successively identified. Notably, K. pneumoniae is the major host of the mcr-8 gene in both animals and humans. This study aims to explore the characteristics of K. pneumoniae strains carrying the mcr-8 gene and tmexCD1-toprJ1 gene cluster and investigate the correlation between these two antibiotic resistance genes.MethodsThe isolates from the poultry farms and the surrounding villages were identified by mass spectrometer, and the strains positive for mcr-1 to mcr-10 were screened by polymerase chain reaction (PCR). The size of the plasmid and the antimicrobial resistance genes carried were confirmed by S1-nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern hybridization, and the transferability of the plasmid was verified by conjugation experiments. Antimicrobial susceptibility testing (AST) and whole genome sequencing (WGS) were used to characterize the strains.ResultsTwo K. pneumoniae isolates (KP26 and KP29) displaying polymyxin resistance were identified as mcr-8 gene carriers. Besides that, tigecycline-resistant gene cluster tmexCD1-toprJ1 was also found on the other plasmid which conferred strain resistance to tigecycline. Through epidemiological analysis, we found that the mcr-8 gene has dispersed globally, circulating in the human, animals, and the environment. Furthermore, our analysis suggests that the coexistence of mcr-8 and tmexCD1-toprJ1 on a single plasmid might evolved through plasmid recombination.ConclusionsAlthough the mcr-8 and tmexCD1-toprJ1 gene clusters in the two strains of K. pneumoniae in this study were on two different plasmids, they still pose a potential threat to public health, requiring close monitoring and further study.