#Octapeptin C4 and #polymyxin #resistance occur via distinct pathways in an epidemic #XDR #Klebsiella pneumoniae ST258 isolate (J Antimicrob Chemother., abstract)

[Source: Journal of Antimicrobial Chemotherapy, full page: (LINK). Abstract, edited.]

Octapeptin C4 and polymyxin resistance occur via distinct pathways in an epidemic XDR Klebsiella pneumoniae ST258 isolate

Miranda E Pitt, Minh Duc Cao, Mark S Butler, Soumya Ramu, Devika Ganesamoorthy, Mark A T Blaskovich, Lachlan J M Coin, Matthew A Cooper

Journal of Antimicrobial Chemotherapy, dky458, https://doi.org/10.1093/jac/dky458

Published: 14 November 2018

 

Abstract

Background

Polymyxin B and E (colistin) have been pivotal in the treatment of XDR Gram-negative bacterial infections; however, resistance has emerged. A structurally related lipopeptide, octapeptin C4, has shown significant potency against XDR bacteria, including polymyxin-resistant strains, but its mode of action remains undefined.

Objectives

We sought to compare and contrast the acquisition of resistance in an XDR Klebsiella pneumoniae (ST258) clinical isolate in vitro with all three lipopeptides to potentially unveil variations in their mode of action.

Methods

The isolate was exposed to increasing concentrations of polymyxins and octapeptin C4 over 20 days. Day 20 strains underwent WGS, complementation assays, antimicrobial susceptibility testing and lipid A analysis.

Results

Twenty days of exposure to the polymyxins resulted in a 1000-fold increase in the MIC, whereas for octapeptin C4 a 4-fold increase was observed. There was no cross-resistance observed between the polymyxin- and octapeptin-resistant strains. Sequencing of polymyxin-resistant isolates revealed mutations in previously known resistance-associated genes, including crrB, mgrB, pmrB, phoPQ and yciM, along with novel mutations in qseC. Octapeptin C4-resistant isolates had mutations in mlaDF and pqiB, genes related to phospholipid transport. These genetic variations were reflected in distinct phenotypic changes to lipid A. Polymyxin-resistant isolates increased 4-amino-4-deoxyarabinose fortification of lipid A phosphate groups, whereas the lipid A of octapeptin C4-resistant strains harboured a higher abundance of hydroxymyristate and palmitoylate.

Conclusions

Octapeptin C4 has a distinct mode of action compared with the polymyxins, highlighting its potential as a future therapeutic agent to combat the increasing threat of XDR bacteria.

Topic: mutation – colistin – genes – klebsiella pneumoniae – lipid a – polymyxins – polymyxin b – epidemics – antimicrobial susceptibility test – gene complementation –

Issue Section: ORIGINAL RESEARCH

Keywords: Antibiotics; Drugs Resistance; Colistin; Polymyxins; Octapentin; K. pneumoniae.

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#Azidothymidine [#AZT] produces synergistic #activity in combination with #colistin against #antibiotic-resistant #Enterobacteriaceae (Antimicrob Agents Chemother., abstract)

[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]

Azidothymidine produces synergistic activity in combination with colistin against antibiotic-resistant Enterobacteriaceae

Yanmin Hu, Yingjun Liu, Anthony Coates

DOI: 10.1128/AAC.01630-18

 

ABSTRACT

Bacterial infections remain the leading killer worldwide which is worsened by the continuous emergence of antibiotic resistance. In particular, antibiotic-resistant Enterobacteriaceae is prevalent and extremely difficult to treat. Reusing existing drugs and rejuvenating the therapeutic potential of existing antibiotics represent an attractive novel strategy. Azidothymidine (AZT) is an antiretroviral drug which is used in combination with other antivirals to prevent and to treat HIV/AIDS. AZT is also active against Gram-negative bacteria but has not been developed for that purpose. Here we investigated in vitro and in vivo efficacy of AZT in combination with colistin against antibiotic-resistant Enterobacteriaceae including extended-spectrum beta-lactamase (ESBL), New Delhi metallo-beta-lactamase 1 (NDM) or the mobilized colistin resistance (mcr-1) producing strains. Minimum inhibitory concentration was determined using the broth microdilution method. The combinatory effect of AZT and colistin was examined using the checkerboard method and time-kill analysis. A murine peritoneal infection model was used to test the therapeutic effect of the combination of AZT and colistin. Fractional inhibitory concentration index from checkerboard assay demonstrated that AZT synergized with colistin against 61% and 87% of ESBL-producing Escherichia coli and Klebsiella pneumoniae, respectively, 100% of NDM-1-producing strains and 92% of mcr-1 producing E. coli. Time-kill analysis demonstrated significant synergistic activities when AZT was combined with colistin. In the murine peritoneal infection model, AZT in combination with colistin showed augmented activities of both drugs in the treatment of NDM-1 K. pneumoniae and mcr-1 E. coli infections. AZT and colistin combination poses a potential to be used coherently to treat antibiotic-resistant Enterobacteriaceae infections.

Copyright © 2018 American Society for Microbiology. All Rights Reserved.

Keywords: Antivirals; Antibiotics; Drugs Resistance; Colistin; AZT; MCR1; Enterobacteriaceae.

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Novel partners with #colistin to increase its in vivo therapeutic effectiveness and prevent the occurrence of colistin #resistance in #NDM- and #MCR-co-producing #Ecoli in a murine infection model (J Antimicrob Chemother., abstract)

[Source: Journal of Antimicrobial Chemotherapy, full page: (LINK). Abstract, edited.]

Novel partners with colistin to increase its in vivotherapeutic effectiveness and prevent the occurrence of colistin resistance in NDM- and MCR-co-producing Escherichia coli in a murine infection model

Yang Yu, Timothy R Walsh, Run-Shi Yang, Mei Zheng, Meng-Chao Wei, Jonathan M Tyrrell, Yang Wang, Xiao-Ping Liao, Jian Sun, Ya-Hong Liu

Journal of Antimicrobial Chemotherapy, dky413, https://doi.org/10.1093/jac/dky413

Published: 20 October 2018

 

Abstract

Objectives

The emergence of NDM- and MCR-1-co-producing Escherichia coli has compromised the use of carbapenems and colistin, which are critically important in clinical therapy, and represents a severe threat to public health worldwide. Here, we demonstrate synergism of colistin combined with existing antibiotics as a potential strategy to overcome XDR E. coli co-harbouring NDM and MCR-1 genes.

Methods

To comprehensively evaluate their combined activity, antibiotic combinations were tested against 34 different E. coli strains carrying both NDM and MCR-1 genes. Antibiotic resistance profiles and molecular characteristics were investigated by susceptibility testing, PCR, MLST, S1-PFGE and WGS. Antibiotic synergistic efficacy was evaluated through in vitro chequerboard experiments and dose–response assays. A mouse model was used to confirm active combination therapies. Additionally, combinations were tested for their ability to prevent high-level colistin-resistant mutants (HLCRMs).

Results

Combinations of colistin with rifampicin, rifabutin and minocycline showed synergistic activity against 34 XDR NDM- and MCR-1-co-producing E. coli strains, restoring, in part, susceptibility to both colistin and the partnering antibiotics. The therapeutic effectiveness of colistin combined with rifampicin or minocycline was demonstrated in a mouse model. Furthermore, colistin plus rifampicin showed significant activity in preventing the occurrence of HLCRMs.

Conclusions

The synergism of colistin in combinations with rifampicin, rifabutin or minocycline offers viable therapeutic alternatives against XDR NDM- and MCR-positive E. coli.

Issue Section: ORIGINAL RESEARCH

© The Author(s) 2018. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.

This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Keywords: Research; Abstracts; Antibiotics; Drugs Resistance; Colistin; E. Coli; Rifampicin; Rifabutin; Minocycline; MCR; NDM.

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#Synergistic antimicrobial #activity of #colistin in combination with #rifampin and #azithromycin against #Escherichia coli producing #MCR-1 (Antimicrob Agents Chemother., abstract)

[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]

Synergistic antimicrobial activity of colistin in combination with rifampin and azithromycin against Escherichia coli producing MCR-1

Yanqin Li, Xiaohuan Lin, Xuan Yao, Yan Huang, Wenguang Liu, Tao Ma, Binghu Fang

DOI: 10.1128/AAC.01631-18

 

ABSTRACT

The lack of available antibiotics is a global public health problem due to the emergence of antimicrobial resistance. Effective therapeutic regimens are urgently needed against Escherichia coli that produces colistin-resistance gene mcr-1 and to inhibit the emergence of resistance. In this study, we assessed the antimicrobial activity of a series of concentrations of colistin-based combinations with rifampin and/or azithromycin against three strains of Escherichia coli, including colistin-resistant isolate MZ1501R, HE1704R that produces MCR-1, and colistin-susceptible isolate MZ1509S. Experiments were conducted at a medium inoculum of ∼107 CFU/mL over 48 h. Subsequently, the in vivo therapeutic effect was investigated using a neutropenic thigh-infected mouse model. Almost all monotherapies showed unsatisfactory antibacterial activity against E. coli isolates producing MCR-1. By contrast, colistin in combination with rifampin or azithromycin resulted in an obvious decrease in bacterial burden, albeit with regrowth. More obviously, synergistic antimicrobial activity of colistin-based triple combination therapy with rifampin and azithromycin was observed, resulting in a rapid and exhaustive antibacterial effect. In vivo treatments confirmed these findings where a mean decrease of 0.38 to 0.90 log10 CFU and 1.27 to 1.78 log10 CFU was noted after 24 h and 48 h of treatment, respectively, against colistin-resistant E. coli strains when 5 mg/kg colistin was combined with rifampin and azithromycin. Colistin-based combinations with rifampin and azithromycin provide a more active therapeutic regimen than monotherapy or colistin-based double combinations against E. coli producing MCR-1.

Copyright © 2018 American Society for Microbiology. All Rights Reserved.

Keywords: Antibiotics; Drugs Resistance; Colistin; E. Coli; MCR1; Azithromycin; Rifampin; Animal models.

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Novel #mcr-5.3 variant in a CTX-M-8-producing #Escherichia coli ST711 isolated from an infected #horse (J Antimicrob Chemother., abstract)

[Source: Journal of Antimicrobial Chemotherapy, full page: (LINK). Abstract, edited.]

Novel mcr-5.3 variant in a CTX-M-8-producing Escherichia coli ST711 isolated from an infected horse

Miriam R Fernandes, Louise Cerdeira, Meire M Silva, Fábio P Sellera, Maria Muñoz, Felicio G Junior, Sergio S Azevedo, Pablo Power, Gabriel Gutkind, Nilton Lincopan

Journal of Antimicrobial Chemotherapy, dky341, https://doi.org/10.1093/jac/dky341

Published: 07 September 2018

___

Sir,

Following the first description of the mobile phosphoethanolamine transferase gene mcr-1, responsible for transferable colistin resistance in Enterobacteriaceae of human and animal origin, a rapid dissemination and emergence of novel mcr variants has been globally described.1–5 

In this regard, two recent reports published in JAC have documented the identification of novel mcr-5 and mcr-5.2 gene variants in d-tartrate fermenting Salmonella enterica subsp. enterica serovar Paratyphi B and Escherichia coli from food and food-producing animals, respectively, in Germany.3,4

Interestingly, mcr-5 has also been identified in E. coli isolates from diseased pigs in Japan6 and from animals…

(…)

Issue Section: Research letter

© The Author(s) 2018. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.

This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Keywords: Antibiotics; Drugs Resistance; Colistin; MCR5; Horses.

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Rapid #detection and discrimination of chromosome- and #MCR-plasmid-mediated #resistance to #polymyxins by MALDI-TOF MS in #Escherichia coli: the MALDIxin test (J Antimicrob Chemother., abstract)

[Source: Journal of Antimicrobial Chemotherapy, full page: (LINK). Abstract, edited.]

Rapid detection and discrimination of chromosome- and MCR-plasmid-mediated resistance to polymyxins by MALDI-TOF MS in Escherichia coli: the MALDIxin test

Laurent Dortet, Remy A Bonnin, Ivana Pennisi, Lauraine Gauthier, Agnès B Jousset, Laura Dabos, R Christopher, D Furniss, Despoina A I Mavridou, Pierre Bogaerts, Youri Glupczynski, Anais Potron, Patrick Plesiat, Racha Beyrouthy, Frédéric Robin, Richard Bonnet, Thierry Naas, Alain Filloux, Gerald Larrouy-Maumus

Journal of Antimicrobial Chemotherapy, dky330, https://doi.org/10.1093/jac/dky330

Published: 01 September 2018

 

Abstract

Background

Polymyxins are currently considered a last-resort treatment for infections caused by MDR Gram-negative bacteria. Recently, the emergence of carbapenemase-producing Enterobacteriaceae has accelerated the use of polymyxins in the clinic, resulting in an increase in polymyxin-resistant bacteria. Polymyxin resistance arises through modification of lipid A, such as the addition of phosphoethanolamine (pETN). The underlying mechanisms involve numerous chromosome-encoded genes or, more worryingly, a plasmid-encoded pETN transferase named MCR. Currently, detection of polymyxin resistance is difficult and time consuming.

Objectives

To develop a rapid diagnostic test that can identify polymyxin resistance and at the same time differentiate between chromosome- and plasmid-encoded resistances.

Methods

We developed a MALDI-TOF MS-based method, named the MALDIxin test, which allows the detection of polymyxin resistance-related modifications to lipid A (i.e. pETN addition), on intact bacteria, in <15 min.

Results

Using a characterized collection of polymyxin-susceptible and -resistant Escherichia coli, we demonstrated that our method is able to identify polymyxin-resistant isolates in 15 min whilst simultaneously discriminating between chromosome- and plasmid-encoded resistance. We validated the MALDIxin test on different media, using fresh and aged colonies and show that it successfully detects all MCR-1 producers in a blindly analysed set of carbapenemase-producing E. coli strains.

Conclusions

The MALDIxin test is an accurate, rapid, cost-effective and scalable method that represents a major advance in the diagnosis of polymyxin resistance by directly assessing lipid A modifications in intact bacteria.

Issue Section: ORIGINAL RESEARCH

© The Author(s) 2018. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.

This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Keywords: Antibiotics; Drugs Resistance; Polymyxin; MCRx; Diagnostic Tests; E. Coli.

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The #bacterial outer #membrane is an evolving #antibiotic #barrier (Proc Natl Acad Sci USA, abstract)

[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]

The bacterial outer membrane is an evolving antibiotic barrier

Kerrie L. May and Marcin Grabowicz

PNAS August 23, 2018. 201812779; published ahead of print August 23, 2018. https://doi.org/10.1073/pnas.1812779115

 

Summary

The outer membrane (OM) of the diderm “gram-negative” class of bacteria is an essential organelle and a robust permeability barrier that prevents many antibiotics from reaching their intracellular targets (1). The OM is a unique asymmetrical lipid bilayer (Fig. 1): The inner leaflet is composed of phospholipids (PLs), and the outer leaflet consists almost exclusively of a glycolipid referred to either as lipopolysaccharide (LPS, in bacteria that attach long repeats of sugars to the glycolipid) or lipooligosaccharide (LOS, in bacteria that attach only a short oligosaccharide to cap the glycolipid) (1). Assembly of these lipids into a contiguous barrier, and how that barrier is maintained in response to damage, is a fascinating biological problem. Both PLs and LPS/LOS are synthesized inside the cell, so they must first transit the inner membrane (IM) and then traverse the hostile aqueous periplasmic environment before being assembled into an OM. Work over the past decade uncovered a protein bridge that links the IM and OM and allows LPS/LOS to flow directly into the OM outer leaflet (2). How PLs are transported to the OM remains a mystery. Understanding the pathways of OM biogenesis is a pressing goal. New antibiotics against gram-negative bacteria are urgently needed (3). Rates of antibiotic resistance continue to rise unabated, while the last truly novel antibiotic effective against gram-negative bacteria was discovered in the 1960s (3). The hope is that treatments interfering with OM biogenesis will offer new lethal therapeutics or will help permeabilize gram-negative bacteria to existing drugs. Until that promise is realized, clinicians are increasingly forced to rely on last-resort antibiotics that were once sidelined due to their unfavorable toxicity profiles, including the OM-targeting antibiotic colistin (polymyxin E) (4). In PNAS, Powers and Trent (5) provide new insights into how colistin-resistant bacteria evolve improved fitness by altering their …

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1 To whom correspondence should be addressed. Email: marcin.grabowicz@emory.edu.

Keywords: Antibiotics; Drugs Resistance; Colistin.

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