scholarly journals First hybrid complete genome ofAeromonas veroniireveals chromosome-mediated novel structural variantmcr-3.19from human clinical specimen

2019 ◽  
Author(s):  
Naveen Kumar Devanga Ragupathi ◽  
Dhiviya Prabaa Muthuirulandi Sethuvel ◽  
Shalini Anandan ◽  
Divya Murugan ◽  
Kalaiarasi Asokan ◽  
...  
Keyword(s):  
Clinical Specimen ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Hybrid Assembly ◽  
Colistin Resistance ◽  
New Variant ◽  
Protein Structural Analysis ◽  
Susceptible Isolate ◽  
Human Clinical Specimen

AbstractBackgroundRecent findings substantiate the origin of plasmid-mediated colistin resistance genemcr-3from Aeromonads. The present study aimed to screen the plasmid-mediated colistin resistance among 30 clinical multidrug resistant (MDR)Aeromonas spp.ResultsThe presence ofmcr-1, mcr-2, mcr-3, and mcr-4were screened by PCR, which revealedmcr-3in a colistin susceptible isolate (FC951). All other isolates were negative formcrgenes. Sequencing of FC951 revealed thatmcr-3(mcr-3.19) identified was different from previously reported variants and had 95.62 and 95.28% nucleotide similarity withmcr-3.3andmcr-3.10gene. A hybrid assembly using IonTorrent and MinION reads revealed structural genetic information ofmcr-3.19with an insertion of ISAs18within the gene. Due to this,mcr-3.19was non-expressive which makes FC951 susceptible to colistin. Further,in silicosequence and protein structural analysis confirmed the new variant. To the best of our knowledge, this is the first report on novelmcr-3variant (mcr-3.19).ConclusionsThe significant role ofmcr-like genes in differentAeromonasspecies remains unknown and needs additional investigation to understand the insights on colistin resistance mechanism.

scholarly journals Genomic Characterization of New Variant of Hydrogen Sulfide (H2S)-Producing Escherichia coli with Multidrug Resistance Properties Carrying the mcr-1 Gene in China

Antibiotics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 80 ◽  
Author(s):  
Silpak Biswas ◽  
Mohammed Elbediwi ◽  
Guimin Gu ◽  
Min Yue
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Sulfide ◽  
Multidrug Resistance ◽  
Bacterial Infections ◽  
Multidrug Resistant ◽  
Health Concern ◽  
Colistin Resistance ◽  
New Variant ◽  
Genomic Characterization ◽  
Human Infections

Colistin is considered to be a ‘last-resort’ antimicrobial for the treatment of multidrug-resistant Gram-negative bacterial infections. Identification of Enterobacteriaceae, carrying the transferable colistin resistance gene mcr-1, has recently provoked a global health concern. This report presents the first detection of a hydrogen sulfide (H2S)-producing Escherichia coli variant isolated from a human in China, with multidrug resistance (MDR) properties, including colistin resistance by the mcr-1 gene, which could have great implications for the treatment of human infections.

scholarly journals Molecular survey of mcr1 and mcr2 plasmid mediated colistin resistance genes in Escherichia coli isolates of animal origin in Iran

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Kayhan Ilbeigi ◽  
Mahdi Askari Badouei ◽  
Hossein Vaezi ◽  
Hassan Zaheri ◽  
Sina Aghasharif ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Resistance Genes ◽  
Companion Animals ◽  
Multidrug Resistant ◽  
Animal Origin ◽  
Colistin Resistance ◽  
E Coli ◽  
High Level ◽  
Farming Industry

Abstract Objectives The emergence of colistin-resistant Enterobacteriaceae from human and animal sources is one of the major public health concerns as colistin is the last-resort antibiotic for treating infections caused by multidrug-resistant Gram-negative bacteria. We aimed to determine the prevalence of the prototype widespread colistin resistance genes (mcr-1 and mcr-2) among commensal and pathogenic Escherichia coli strains isolated from food-producing and companion animals in Iran. Results A total of 607 E. coli isolates which were previously collected from different animal sources between 2008 and 2016 used to uncover the possible presence of plasmid-mediated colistin resistance genes (mcr-1 and mcr-2) by PCR. Overall, our results could not confirm the presence of any mcr-1 or mcr-2 positive E. coli among the studied isolates. It is concluded that despite the important role of food-producing animals in transferring the antibiotic resistance, they were not the main source for carriage of mcr-1 and mcr-2 in Iran until 2016. This study suggests that the other mcr variants (mcr-3 to mcr-9) might be responsible for conferring colistin resistance in animal isolates in Iran. The possible linkage between pig farming industry and high level of mcr carriage in some countries needs to be clarified in future prospective studies.

scholarly journals Colistin heteroresistance and the involvement of the PmrAB regulatory system in Acinetobacter baumannii

2018 ◽  
Author(s):  
Yannick Charretier ◽  
Seydina M. Diene ◽  
Damien Baud ◽  
Sonia Chatellier ◽  
Emmanuelle Santiago-Allexant ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Population Analysis ◽  
Regulatory System ◽  
Clinical Problem ◽  
Multidrug Resistant ◽  
Regulatory Pathway ◽  
Colistin Resistance ◽  
Bacterial Killing ◽  
One Step

AbstractMultidrug-resistant Acinetobacter baumannii infection has recently emerged as a worldwide clinical problem and colistin is increasingly being used as last resort therapy. Despite its favorable bacterial killing, resistance and heteroresistance to colistin have been described. Mutations in the PmrAB regulatory pathway have been already associated with colistin resistance whereas the mechanisms for heteroresistance remain largely unknown. The purpose of the present study is to investigate the role of PmrAB in laboratory-selected mutants representative of global epidemic strains. During brief colistin exposure, colistin resistant and colistin heteroresistant mutants were selected in a one-step strategy. Population Analysis Profiling (PAP) was performed to confirm the suspected phenotype. Upon withdrawal of selective pressure, compensatory mutations were evaluated in another one-step strategy. A trans-complementation assay was designed to delineate the involvement of the PmrAB regulatory system using qPCR and PAP. Mutations in the PmrAB regulatory pathway were associated with colistin resistance and colistin heteroresistance as well. The transcomplementation assay provides a proof for the role played by changes in the PmrAB regulatory pathway. The level of colistin resistance is correlated to the level of expression of pmrC. The resistance phenotype was partially restored since the complemented strain became heteroresistant. This report shows the role of different mutations in the PmrAB regulatory pathway and warns on the development of colistin heteroresistance that could be present but not easily detected with routine testing.

scholarly journals Exogenous and Endogenous Phosphoethanolamine Transferases Differently Affect Colistin Resistance and Fitness in Pseudomonas aeruginosa

2021 ◽  
Vol 12 ◽  
Author(s):  
Matteo Cervoni ◽  
Alessandra Lo Sciuto ◽  
Chiara Bianchini ◽  
Carmine Mancone ◽  
Francesco Imperi
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Lipid A ◽  
Cell Envelope ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Transferase Activity ◽  
Colistin Resistance ◽  
Phosphoethanolamine Transferases ◽  
Positively Charged ◽  
Inducible Gene

Colistin represents a last-line treatment option for infections caused by multidrug resistant Gram-negative pathogens, including Pseudomonas aeruginosa. Colistin resistance generally involves the modification of the lipid A moiety of lipopolysaccharide (LPS) with positively charged molecules, namely phosphoethanolamine (PEtN) or 4-amino-4-deoxy-L-arabinose (Ara4N), that reduce colistin affinity for its target. Several lines of evidence highlighted lipid A aminoarabinosylation as the primary colistin resistance mechanism in P. aeruginosa, while the contribution of phosphoethanolamination remains elusive. PEtN modification can be due to either endogenous (chromosomally encoded) PEtN transferase(s) (e.g., EptA in P. aeruginosa) or plasmid borne MCR enzymes, commonly found in enterobacteria. By individually cloning eptA and mcr-1 into a plasmid for inducible gene expression, we demonstrated that MCR-1 and EptA have comparable PEtN transferase activity in P. aeruginosa and confer colistin resistance levels similar to those provided by lipid A aminoarabinosylation. Notably, EptA, but not MCR-1, negatively affects P. aeruginosa growth and, to a lesser extent, cell envelope integrity when expressed at high levels. Mutagenesis experiments revealed that PEtN transferase activity does not account for the noxious effects of EptA overexpression, that instead requires a C-terminal tail unique to P. aeruginosa EptA, whose function remains unknown. Overall, this study shows that both endogenous and exogenous PEtN transferases can promote colistin resistance in P. aeruginosa, and that PEtN and MCR-1 mediated resistance has no impact on growth and cell envelope homeostasis, suggesting that there may be no fitness barriers to the spread of mcr-1 in P. aeruginosa.

scholarly journals First Report of the mcr-1 colistin Resistance Gene Identified in Escherichia coli Isolated from a Clinical Sample in Naples in 2020

2020 ◽  
Author(s):  
BIAGIO SANTELLA ◽  
CARLA ZANNELLA ◽  
CHIARA DEL VECCHIO ◽  
ANNALISA CHIANESE ◽  
VERONICA FOLLIERO ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Resistance Gene ◽  
Clinical Sample ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Health Concern ◽  
Colistin Resistance ◽  
Gram Negative ◽  
E Coli ◽  
Carbapenem Resistant

Abstract Background: The emergence of a novel plasmid-mediated colistin resistance mechanism, encoded by the mcr-1 gene, represents a major public health concern. The mechanism of resistance to colistin, mediated by plasmids, is a serious problem, both for its ability to be transferred to other species, and for infections caused by carbapenem-resistant Gram-negative, in which colistin is used as an antimicrobial drug of last line for the treatment of these infections. The present study highlights the first isolation and genetic evaluation of detecting plasmid-mediated resistance to colistin in a multidrug-resistant (MDR) Escherichia coli (E. coli) isolated from a clinical sample in the metropolitan city of Naples, Italy. Results: Colistin-resistant E. coli isolate was identified in August 2020 from the blood culture of a male patient with multiple comorbidities. The minimum inhibitory concentration (MIC) of colistin was 8 mg/L. In addition to colistin, the isolate was resistant to third-generation cephalosporins (cefotaxime and ceftazidime), penicillin (amoxicillin and piperacillin), aminoglycosides (gentamicin and tobramycin), and fluoroquinolones (ciprofloxacin and levofloxacin). However, it showed susceptibility to carbapenems (ertapenem, imipenem, and meropenem), tetracyclines (tigecycline), and piperacillin-tazobactam. The results of the PCR confirmed the presence of the mcr-1 resistance gene. Conclusion: This study confirms the presence of resistance to colistin mediated by the mcr-1 gene in a clinical isolate of E. coli. Although resistance to colistin caused by the mcr-1 gene is not common in our region, it should not be ignored. Therefore, further surveillance studies are recommended to monitor the spread of plasmid-mediated colistin resistance genes in Gram-negative MDR bacteria.

scholarly journals Phage Resistance Mechanisms Increase Colistin Sensitivity in Acinetobacter baumannii

2021 ◽  
Author(s):  
Xiaoqing Wang ◽  
Belinda Loh ◽  
Yunsong Yu ◽  
Xiaoting Hua ◽  
Sebastian Leptihn
Keyword(s):  
Bacterial Infections ◽  
Bacterial Resistance ◽  
Phage Therapy ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Resistant Bacteria ◽  
Phage Resistance ◽  
Colistin Resistance ◽  
Increased Sensitivity

Few emergency-use antibiotics remain for the treatment of multidrug-resistant bacterial infections. Infections with resistant bacteria are becoming increasingly common. Phage therapy has reemerged as a promising strategy to treat such infections, as microbial viruses are not affected by bacterial resistance to antimicrobial compounds. However, phage therapy is impeded by rapid emergence of phage-resistant bacteria during therapy. In this work, we studied phage-resistance of colistin sensitive and resistant A. baumannii strains. Using whole genome sequencing, we determined that phage resistant strains displayed mutations in genes that alter the architecture of the bacterial envelope. In contrast to previous studies where phage-escape mutants showed decreased binding of phages to the bacterial envelope, we obtained several not uninfectable isolates that allowed similar phage adsorption compared to the susceptible strain. When phage-resistant bacteria emerged in the absence of antibiotics, we observed that the colistin resistance levels often decreased, while the antibiotic resistance mechanism per se remained unaltered. In particular the two mutated genes that conveyed phage resistance, a putative amylovoran- biosynthesis and a lipo-oligosaccharide (LOS) biosynthesis gene, impact colistin resistance as the mutations increased sensitivity to the antibiotic.

scholarly journals In VitroActivity of Imipenem-Relebactam Alone or in Combination with Amikacin or Colistin againstPseudomonas aeruginosa

2019 ◽  
Vol 63 (9) ◽  
Author(s):  
Tomefa E. Asempa ◽  
David P. Nicolau ◽  
Joseph L. Kuti
Keyword(s):  
Potential Role ◽  
Multidrug Resistant ◽  
Synergistic Activity ◽  
Content Type ◽  
Class A ◽  
Susceptible Isolate ◽  
Time Kill ◽  
Lactamase Inhibitor

ABSTRACTRelebactam is a novel class A/C β-lactamase inhibitor that restores imipenemin vitroactivity against multidrug-resistant and carbapenem-nonsusceptiblePseudomonas aeruginosa. Time-kill analyses were performed to evaluate the potential role of imipenem-relebactam in combination with amikacin or colistin againstP. aeruginosa. Ten clinicalP. aeruginosaisolates (9 imipenem nonsusceptible) with imipenem-relebactam MICs ranging from 1/4 to 8/4 μg/ml were included. The isolates had varied susceptibilities to imipenem (1 to 32 μg/ml), amikacin (4 to 128 μg/ml), and colistin (0.5 to 1 μg/ml). Duplicate 24-h time-kill studies were conducted using the average steady-state concentrations (Cssavg) observed after the administration of imipenem-relebactam at 500 mg/250 mg every 6 hours (q6h) alone and in combination with theCssavgof 25 mg/kg of body weight/day amikacin and 360 mg/day colistin in humans. Imipenem-relebactam alone resulted in 24-h bacterial densities of −2.93 ± 0.38, −1.67 ± 0.29, +0.38 ± 0.96, and +0.15 ± 0.65 log10CFU/ml at imipenem-relebactam MICs of 1/4, 2/4, 4/4, and 8/4 μg/ml, respectively. No synergy was demonstrated against the single imipenem-susceptible isolate. Against the imipenem-nonsusceptible isolates (n = 9), imipenem-relebactam combined with amikacin resulted in synergy (−2.61 ± 1.50 log10CFU/ml) against all amikacin-susceptible isolates and in two of three amikacin-intermediate (i.e., MIC, 32 μg/ml) isolates (−2.06 ± 0.19 log10CFU/ml). Synergy with amikacin was not observed when the amikacin MIC was >32 μg/ml. Imipenem-relebactam combined with colistin demonstrated synergy in eight out of the nine imipenem-resistant isolates (−3.17 ± 1.00 log10CFU/ml). Against these 10 P. aeruginosaisolates, imipenem-relebactam combined with either amikacin or colistin resulted in synergistic activity against the majority of strains. Further studies evaluating combination therapy with imipenem-relebactam are warranted.

scholarly journals Role of Oxidative Stress in Persister Tolerance

2012 ◽  
Vol 56 (9) ◽  
pp. 4922-4926 ◽  
Author(s):  
Yanxia Wu ◽  
Marin Vulić ◽  
Iris Keren ◽  
Kim Lewis
Keyword(s):  
Oxidative Stress ◽  
Stress Responses ◽  
Resistance Mechanism ◽  
Sos Response ◽  
Multidrug Resistant ◽  
Activated Macrophages ◽  
Chronic Infections ◽  
Persister Cells ◽  
Fluoroquinolone Antibiotics

ABSTRACTPersisters are dormant phenotypic variants of regular cells that are tolerant to antibiotics and play an important role in recalcitrance of chronic infections to therapy. Persisters can be produced stochastically in a population untreated with antibiotics. At the same time, a deterministic component of persister formation has also been documented in a population of cells with DNA damaged by fluoroquinolone treatment. Expression of the SOS response under these conditions induces formation of persisters by increasing expression of the TisB toxin. This suggests that other stress responses may also contribute to persister formation. Of particular interest is oxidative stress that pathogens encounter during infection. Activated macrophages produce reactive oxygen and nitrogen species which induce the SoxRS and OxyR regulons. Genes controlled by these regulons deactivate the oxidants and promote repair. We examined the ability of oxidative stress induced by paraquat (PQ) to affect persister formation. Preincubation of cells with PQ produced a dramatic increase in the number of persisters surviving challenge with fluoroquinolone antibiotics. PQ did not affect killing by kanamycin or ampicillin. Persisters in a culture treated with PQ that survived a challenge with a fluoroquinolone were also highly tolerant to other antibiotics. PQ induces SoxRS, which in turn induces expression of the AcrAB-TolC multidrug-resistant (MDR) pump. Fluoroquinolones are extruded by this MDR pump, and the effect of PQ on antibiotic tolerance was largely abolished in a mutant that was defective in the pump. It appears that PQ, acting through AcrAB-TolC, reduces the concentration of fluoroquinolones in the cells. This allows a larger fraction of cells to become persisters in the presence of a fluoroquinolone. Analysis of alexA3mutant indeed showed a dependence of persister induction under these conditions on SOS. These findings show that induction of a classical resistance mechanism, MDR efflux, by oxidative stress leads to an increase in multidrug-tolerant persister cells.

scholarly journals In Vivo Development of Polymyxin B Resistance in Klebsiella pneumoniae owing to a 42 bp Deletion in the Sequence of phoQ

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Qingqing Xu ◽  
Teng Xu ◽  
Yuan Zhuang ◽  
Xiaofen Liu ◽  
Ying Li ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Resistance Mechanism ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Resistant Isolate ◽  
Pcr Analysis ◽  
Qrt Pcr ◽  
Susceptible Isolate ◽  
Periplasmic Domain

Polymyxins resistance has emerged worldwide and is threatening the treatment efficacy of multidrug resistant Klebsiella pneumoniae in humans and animals. In this research, we employed whole-genome sequencing (WGS) to investigate the polymyxin B resistance mechanism in selected polymyxin B-susceptible and polymyxin B-resistant K. pneumoniae, isolated from one patient of Huashan Hospital affiliated to Fudan University. The WGS results showed that the two K. pneumoniae all belong to ST11. The average nucleotide identity between the two K. pneumoniae was nearly 100%. No sense mutations of polymyxins resistance associated genes (pmrA, pmrB, phoP, mgrB) were observed in polymyxin B-resistant K. pneumonia (PRKP) compared to the polymyxin B-susceptible isolate. A 42 bp deletion was found in the sequence of phoQ in PRKP. The deletion of amino acid occurred on the periplasmic domain of PhoQ protein. We speculate that this is the domain that MgrB protein interact with the PhoQ protein and negatively regulate the PhoP/PhoQ system. qRT-PCR analysis revealed an overexpression of the pmrA (6.8-fold), pmrB (151.9-fold), pmrC (14.5-fold), pmrK (287.9-fold), phoP (14.5-fold), and phoQ (16.8-fold) genes in the polymyxin B-resistant isolate compared to the expression of the polymyxin B-susceptible K. pneumoniae isolate, suggesting that the phoQ deletion maybe responsible for the increased expression levels of those genes. In conclusion, this study identified a 42 bp deletion in the sequence of phoQ as being responsible for the overexpression of pmrCAB and pmrHFIJKLM operons, leading to resistance to polymyxin B.

scholarly journals Molecular Insights into Functional Differences between mcr-3- and mcr-1-Mediated Colistin Resistance

2018 ◽  
Vol 62 (9) ◽  
Author(s):  
Hui Li ◽  
Lu Yang ◽  
Zhihai Liu ◽  
Wenjuan Yin ◽  
Dejun Liu ◽  
...  
Keyword(s):  
Lipid A ◽  
Catalytic Mechanism ◽  
Sequence Divergence ◽  
Multidrug Resistant ◽  
Site Directed Mutagenesis ◽  
Head Group ◽  
Colistin Resistance ◽  
Flight Mass Spectrometry ◽  
Functional Differences

ABSTRACT The global emergence of plasmid-mediated colistin resistance genes mcr-1 and mcr-3 has threatened the role of the “last-resort” drug colistin in the defense against infections caused by multidrug-resistant Gram-negative bacteria. However, functional differences between these two genes in mediating colistin resistance remain poorly understood. Protein sequence alignment of MCR-3 and MCR-1 was therefore conducted in Clustal Omega to identify sequence divergence. The molecular recognition of lipid A head group phosphatidylethanolamine and MCR-3 enzyme was studied by homology modeling and molecular docking, with the catalytic mechanism of MCR-3 also being explored. Thr277 in MCR-3 was validated as the key amino acid residue responsible for the catalytic reaction using site-directed mutagenesis and was shown to act as a nucleophile. Lipid A modification induced by the MCR-3 and MCR-1 enzymes was confirmed by electrospray ionization–time of flight mass spectrometry. Far-UV circular dichroism spectra of the MCR-3 and MCR-1 enzymes suggested that MCR-3 was more thermostable than MCR-1, with a melting temperature of 66.19°C compared with 61.14°C for MCR-1. These data provided molecular insight into the functional differences between mcr-3 and mcr-1 in conferring colistin resistance.

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