scholarly journals Clinically Relevant Antibiotic Resistance Mechanisms Can Enhance the In Vivo Fitness of Neisseria gonorrhoeae

10.5772/29449 ◽  
2012 ◽  
Author(s):  
Elizabeth A. ◽  
Jonathan A. ◽  
Anjali N. ◽  
Ann E. ◽  
William M.
Keyword(s):  
Antibiotic Resistance ◽  
Neisseria Gonorrhoeae ◽  
Resistance Mechanisms

scholarly journals Quinolone Resistance Reversion by Targeting the SOS Response

mBio ◽  
2017 ◽  
Vol 8 (5) ◽  
Author(s):  
E. Recacha ◽  
J. Machuca ◽  
P. Díaz de Alba ◽  
M. Ramos-Güelfo ◽  
F. Docobo-Pérez ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Antimicrobial Agents ◽  
Sos Response ◽  
Resistance Mechanisms ◽  
Quinolone Resistance ◽  
Resistant Bacteria ◽  
Health Crisis ◽  
E Coli ◽  
Isogenic Strains

ABSTRACT Suppression of the SOS response has been postulated as a therapeutic strategy for potentiating antimicrobial agents. We aimed to evaluate the impact of its suppression on reversing resistance using a model of isogenic strains of Escherichia coli representing multiple levels of quinolone resistance. E. coli mutants exhibiting a spectrum of SOS activity were constructed from isogenic strains carrying quinolone resistance mechanisms with susceptible and resistant phenotypes. Changes in susceptibility were evaluated by static (MICs) and dynamic (killing curves or flow cytometry) methodologies. A peritoneal sepsis murine model was used to evaluate in vivo impact. Suppression of the SOS response was capable of resensitizing mutant strains with genes encoding three or four different resistance mechanisms (up to 15-fold reductions in MICs). Killing curve assays showed a clear disadvantage for survival (Δlog10 CFU per milliliter [CFU/ml] of 8 log units after 24 h), and the in vivo efficacy of ciprofloxacin was significantly enhanced (Δlog10 CFU/g of 1.76 log units) in resistant strains with a suppressed SOS response. This effect was evident even after short periods (60 min) of exposure. Suppression of the SOS response reverses antimicrobial resistance across a range of E. coli phenotypes from reduced susceptibility to highly resistant, playing a significant role in increasing the in vivo efficacy. IMPORTANCE The rapid rise of antibiotic resistance in bacterial pathogens is now considered a major global health crisis. New strategies are needed to block the development of resistance and to extend the life of antibiotics. The SOS response is a promising target for developing therapeutics to reduce the acquisition of antibiotic resistance and enhance the bactericidal activity of antimicrobial agents such as quinolones. Significant questions remain regarding its impact as a strategy for the reversion or resensitization of antibiotic-resistant bacteria. To address this question, we have generated E. coli mutants that exhibited a spectrum of SOS activity, ranging from a natural SOS response to a hypoinducible or constitutively suppressed response. We tested the effects of these mutations on quinolone resistance reversion under therapeutic concentrations in a set of isogenic strains carrying different combinations of chromosome- and plasmid-mediated quinolone resistance mechanisms with susceptible, low-level quinolone resistant, resistant, and highly resistant phenotypes. Our comprehensive analysis opens up a new strategy for reversing drug resistance by targeting the SOS response. IMPORTANCE The rapid rise of antibiotic resistance in bacterial pathogens is now considered a major global health crisis. New strategies are needed to block the development of resistance and to extend the life of antibiotics. The SOS response is a promising target for developing therapeutics to reduce the acquisition of antibiotic resistance and enhance the bactericidal activity of antimicrobial agents such as quinolones. Significant questions remain regarding its impact as a strategy for the reversion or resensitization of antibiotic-resistant bacteria. To address this question, we have generated E. coli mutants that exhibited a spectrum of SOS activity, ranging from a natural SOS response to a hypoinducible or constitutively suppressed response. We tested the effects of these mutations on quinolone resistance reversion under therapeutic concentrations in a set of isogenic strains carrying different combinations of chromosome- and plasmid-mediated quinolone resistance mechanisms with susceptible, low-level quinolone resistant, resistant, and highly resistant phenotypes. Our comprehensive analysis opens up a new strategy for reversing drug resistance by targeting the SOS response.

scholarly journals Update on Antimicrobial Resistance in Clostridium difficile: Resistance Mechanisms and Antimicrobial Susceptibility Testing

2017 ◽  
Vol 55 (7) ◽  
pp. 1998-2008 ◽  
Author(s):  
Zhong Peng ◽  
Dazhi Jin ◽  
Hyeun Bum Kim ◽  
Charles W. Stratton ◽  
Bin Wu ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Clostridium Difficile ◽  
Gene Mutations ◽  
Antibiotic Resistance Genes ◽  
Resistance Mechanisms ◽  
Test Methods ◽  
Genotypic Resistance ◽  
Altered Expression ◽  
Content Type

ABSTRACT Oral antibiotics such as metronidazole, vancomycin and fidaxomicin are therapies of choice for Clostridium difficile infection. Several important mechanisms for C. difficile antibiotic resistance have been described, including the acquisition of antibiotic resistance genes via the transfer of mobile genetic elements, selective pressure in vivo resulting in gene mutations, altered expression of redox-active proteins, iron metabolism, and DNA repair, as well as via biofilm formation. This update summarizes new information published since 2010 on phenotypic and genotypic resistance mechanisms in C. difficile and addresses susceptibility test methods and other strategies to counter antibiotic resistance of C. difficile .

scholarly journals Porin-Mediated Antibiotic Resistance in Neisseria gonorrhoeae: Ion, Solute, and Antibiotic Permeation through PIB Proteins with penB Mutations

2006 ◽  
Vol 188 (7) ◽  
pp. 2300-2308 ◽  
Author(s):  
Melanie Olesky ◽  
Shuqing Zhao ◽  
Robert L. Rosenberg ◽  
Robert A. Nicholas
Keyword(s):  
Antibiotic Resistance ◽  
Neisseria Gonorrhoeae ◽  
Lipid Bilayers ◽  
Efflux Pump ◽  
Wild Type ◽  
Electrophysiological Properties ◽  
Anion Selectivity ◽  
Resistance To Penicillin ◽  
Level Resistance

ABSTRACT Neisseria gonorrhoeae has two porins, PIA and PIB, whose genes (porA and porB, respectively) are alleles of a single por locus. We recently demonstrated that penB mutations at positions 120 and 121 in PIB, which are presumed to reside in loop 3 that forms the pore constriction zone, confer intermediate-level resistance to penicillin and tetracycline (M. Olesky, M. Hobbs, and R. A. Nicholas, Antimicrob. Agents Chemother. 46:2811-2820, 2002). In the present study, we investigated the electrophysiological properties as well as solute and antibiotic permeation rates of recombinant PIB proteins containing penB mutations (G120K, G120D/A121D, G120P/A121P, and G120R/A121H). In planar lipid bilayers, the predominant conducting state of each porin variant was 30 to 40% of the wild type, even though the anion selectivity and maximum channel conductance of each PIB variant was similar to that of the wild type. Liposome-swelling experiments revealed no significant differences in the permeation of sugars or β-lactam antibiotics through the wild type or PIB variants. Although these results are seemingly contradictory with the ability of these variants to increase antibiotic resistance, they are consistent with MIC data showing that these porin mutations confer resistance only in strains containing an mtrR mutation, which increases expression of the MtrC-MtrD-MtrE efflux pump. Moreover, both the mtrR and penB mutations were required to decrease in vivo permeation rates below those observed in the parental strain containing either mtrR or porin mutations alone. Thus, these data demonstrate a novel mechanism of porin-mediated resistance in which mutations in PIB have no affect on antibiotic permeation alone but instead act synergistically with the MtrC-MtrD-MtrE efflux pump in the development of antibiotic resistance in gonococci.

scholarly journals In vivo protein interaction network analysis reveals porin-localized antibiotic inactivation in Acinetobacter baumannii strain AB5075

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Xia Wu ◽  
Juan D. Chavez ◽  
Devin K. Schweppe ◽  
Chunxiang Zheng ◽  
Chad R. Weisbrod ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Protein Interaction ◽  
Protein Interaction Network ◽  
Outer Membrane Proteins ◽  
Interaction Network ◽  
Resistance Mechanisms ◽  
Clinical Strain

Abstract The nosocomial pathogen Acinetobacter baumannii is a frequent cause of hospital-acquired infections worldwide and is a challenge for treatment due to its evolved resistance to antibiotics, including carbapenems. Here, to gain insight on A. baumannii antibiotic resistance mechanisms, we analyse the protein interaction network of a multidrug-resistant A. baumannii clinical strain (AB5075). Using in vivo chemical cross-linking and mass spectrometry, we identify 2,068 non-redundant cross-linked peptide pairs containing 245 intra- and 398 inter-molecular interactions. Outer membrane proteins OmpA and YiaD, and carbapenemase Oxa-23 are hubs of the identified interaction network. Eighteen novel interactors of Oxa-23 are identified. Interactions of Oxa-23 with outer membrane porins OmpA and CarO are verified with co-immunoprecipitation analysis. Furthermore, transposon mutagenesis of oxa-23 or interactors of Oxa-23 demonstrates changes in meropenem or imipenem sensitivity in strain AB5075. These results provide a view of porin-localized antibiotic inactivation and increase understanding of bacterial antibiotic resistance mechanisms.

scholarly journals LpxC Inhibitors as New Antibacterial Agents and Tools for Studying Regulation of Lipid A Biosynthesis in Gram-Negative Pathogens

mBio ◽  
2014 ◽  
Vol 5 (5) ◽  
Author(s):  
Andrew P. Tomaras ◽  
Craig J. McPherson ◽  
Michael Kuhn ◽  
Arlene Carifa ◽  
Lisa Mullins ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Lipid A ◽  
Resistance Mechanisms ◽  
Gram Negative ◽  
Content Type ◽  
Cellular Targets ◽  
Depth Analysis ◽  
Lipid A Biosynthesis

ABSTRACT The problem of multidrug resistance in serious Gram-negative bacterial pathogens has escalated so severely that new cellular targets and pathways need to be exploited to avoid many of the preexisting antibiotic resistance mechanisms that are rapidly disseminating to new strains. The discovery of small-molecule inhibitors of LpxC, the enzyme responsible for the first committed step in the biosynthesis of lipid A, represents a clinically unprecedented strategy to specifically act against Gram-negative organisms such as Pseudomonas aeruginosa and members of the Enterobacteriaceae. In this report, we describe the microbiological characterization of LpxC-4, a recently disclosed inhibitor of this bacterial target, and demonstrate that its spectrum of activity extends to several of the pathogenic species that are most threatening to human health today. We also show that spontaneous generation of LpxC-4 resistance occurs at frequencies comparable to those seen with marketed antibiotics, and we provide an in-depth analysis of the mechanisms of resistance utilized by target pathogens. Interestingly, these isolates also served as tools to further our understanding of the regulation of lipid A biosynthesis and enabled the discovery that this process occurs very distinctly between P. aeruginosa and members of the Enterobacteriaceae. Finally, we demonstrate that LpxC-4 is efficacious in vivo against multiple strains in different models of bacterial infection and that the major first-step resistance mechanisms employed by the intended target organisms can still be effectively treated with this new inhibitor. IMPORTANCE New antibiotics are needed for the effective treatment of serious infections caused by Gram-negative pathogens, and the responsibility of identifying new drug candidates rests squarely on the shoulders of the infectious disease community. The limited number of validated cellular targets and approaches, along with the increasing amount of antibiotic resistance that is spreading throughout the clinical environment, has prompted us to explore the utility of inhibitors of novel targets and pathways in these resistant organisms, since preexisting target-based resistance should be negligible. Lipid A biosynthesis is an essential process for the formation of lipopolysaccharide, which is a critical component of the Gram-negative outer membrane. In this report, we describe the in vitro and in vivo characterization of novel inhibitors of LpxC, an enzyme whose activity is required for proper lipid A biosynthesis, and demonstrate that our lead compound has the requisite attributes to warrant further consideration as a novel antibiotic.

scholarly journals Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant Staphylococcus aureus

mSystems ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Michael J. Salazar ◽  
Henrique Machado ◽  
Nicholas A. Dillon ◽  
Hannah Tsunemoto ◽  
Richard Szubin ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Resistance Mechanisms ◽  
Evolutionary Strategy ◽  
Continuous Exposure ◽  
Adaptive Laboratory Evolution ◽  
Laboratory Evolution ◽  
Methicillin Resistant ◽  
Content Type

ABSTRACT Antimicrobial susceptibility testing standards driving clinical decision-making have centered around the use of cation-adjusted Mueller-Hinton broth (CA-MHB) as the medium with the notion of supporting bacterial growth, without consideration of recapitulating the in vivo environment. However, it is increasingly recognized that various medium conditions have tremendous influence on antimicrobial activity, which in turn may have major implications on the ability of in vitro susceptibility assays to predict antibiotic activity in vivo. To elucidate differential growth optimization and antibiotic resistance mechanisms, adaptive laboratory evolution was performed in the presence or absence of the antibiotic nafcillin with methicillin-resistant Staphylococcus aureus (MRSA) TCH1516 in either (i) CA-MHB, a traditional bacteriological nutritionally rich medium, or (ii) Roswell Park Memorial Institute (RPMI), a medium more reflective of the in vivo host environment. Medium adaptation analysis showed an increase in growth rate in RPMI, but not CA-MHB, with mutations in apt, adenine phosphoribosyltransferase, and the manganese transporter subunit, mntA, occurring reproducibly in parallel replicate evolutions. The medium-adapted strains showed no virulence attenuation. Continuous exposure of medium-adapted strains to increasing concentrations of nafcillin led to medium-specific evolutionary strategies. Key reproducibly occurring mutations were specific for nafcillin adaptation in each medium type and did not confer resistance in the other medium environment. Only the vraRST operon, a regulator of membrane- and cell wall-related genes, showed mutations in both CA-MHB- and RPMI-evolved strains. Collectively, these results demonstrate the medium-specific genetic adaptive responses of MRSA and establish adaptive laboratory evolution as a platform to study clinically relevant resistance mechanisms. IMPORTANCE The ability of pathogens such as Staphylococcus aureus to evolve resistance to antibiotics used in the treatment of infections has been an important concern in the last decades. Resistant acquisition usually translates into treatment failure and puts patients at risk of unfavorable outcomes. Furthermore, the laboratory testing of antibiotic resistance does not account for the different environment the bacteria experiences within the human body, leading to results that do not translate into the clinic. In this study, we forced methicillin-resistant S. aureus to develop nafcillin resistance in two different environments, a laboratory environment and a physiologically more relevant environment. This allowed us to identify genetic changes that led to nafcillin resistance under both conditions. We concluded that not only does the environment dictate the evolutionary strategy of S. aureus to nafcillin but also that the evolutionary strategy is specific to that given environment.

scholarly journals Clinically Relevant Gram-Negative Resistance Mechanisms Have No Effect on the Efficacy of MC-1, a Novel Siderophore-Conjugated Monocarbam

2012 ◽  
Vol 56 (12) ◽  
pp. 6334-6342 ◽  
Author(s):  
Craig J. McPherson ◽  
Lisa M. Aschenbrenner ◽  
Brian M. Lacey ◽  
Kelly C. Fahnoe ◽  
Margaret M. Lemmon ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Outer Membrane ◽  
Negative Resistance ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Gram Negative ◽  
Content Type ◽  
Pharmacologically Active

ABSTRACTThe incidence of hospital-acquired infections with multidrug-resistant (MDR) Gram-negative pathogens is increasing at an alarming rate. Equally alarming is the overall lack of efficacious therapeutic options for clinicians, which is due primarily to the acquisition and development of various antibiotic resistance mechanisms that render these drugs ineffective. Among these mechanisms is the reduced permeability of the outer membrane, which prevents many marketed antibiotics from traversing this barrier. To circumvent this, recent drug discovery efforts have focused on conjugating a siderophore moiety to a pharmacologically active compound that has been designed to hijack the bacterial siderophore transport system and trick cells into importing the active drug by recognizing it as a nutritionally beneficial compound. MC-1, a novel siderophore-conjugated β-lactam that promotes its own uptake into bacteria, has exquisite activity against many Gram-negative pathogens. While the inclusion of the siderophore was originally designed to facilitate outer membrane penetration into Gram-negative cells, here we show that this structural moiety also renders other clinically relevant antibiotic resistance mechanisms unable to affect MC-1 efficacy. Resistance frequency determinations and subsequent characterization of first-step resistant mutants identified PiuA, a TonB-dependent outer membrane siderophore receptor, as the primary means of MC-1 entry intoPseudomonas aeruginosa. While the MICs of these mutants were increased 32-fold relative to the parental strainin vitro, we show that this resistance phenotype is not relevantin vivo, as alternative siderophore-mediated uptake mechanisms compensated for the loss of PiuA under iron-limiting conditions.

Evaluation of Potent Isoquinoline-Based Thiosemicarbazone Antiproliferatives Against Solid Tumor Models

2019 ◽  
Author(s):  
Daniel Sun ◽  
Soumya Poddar ◽  
Roy D. Pan ◽  
Juno Van Valkenburgh ◽  
Ethan Rosser ◽  
...  
Keyword(s):  
Solid Tumor ◽  
Small Cell Lung Carcinoma ◽  
Single Agent ◽  
Resistance Mechanisms ◽  
Tumor Models ◽  
Cell Lung Carcinoma ◽  
Adaptive Resistance ◽  
Cancer Models ◽  
Nanomolar Range

The lead compound, an ⍺-N-heterocyclic carboxaldehyde thiosemicarbazone <b>HCT-13</b>, was highly potent against a panel of pancreatic, small cell lung carcinoma, and prostate cancer models, with IC<sub>90</sub> values in the low-to-mid nanomolar range.<b> </b>We show that the cytotoxicity of <b>HCT-13</b> is copper-dependent, that it acts as a copper ionophore, induces production of reactive oxygen species (ROS), and promotes mitochondrial dysfunction and S-phase arrest. Lastly, DNA damage response/replication stress response (DDR/RSR) pathways, specifically Ataxia-Telangiectasia Mutated (ATM) and Rad3-related protein kinase (ATR), were identified as actionable adaptive resistance mechanisms following <b>HCT-13 </b>treatment. Taken together, <b>HCT-13 </b>is potent against solid tumor models and warrants <i>in vivo</i> evaluation against aggressive tumor models, either as a single agent or as part of a combination therapy.

MICROORGANISMS ANTIBIOTIC RESISTANCE MECHANISMS – PRESENT VIEW

2019 ◽  
Vol 21 (10) ◽  
pp. 125-130
Author(s):  
Пушилина А.Д. ◽  
◽  
Коменкова Т.С. ◽  
Зайцева Е.А. ◽  
Keyword(s):  
Antibiotic Resistance ◽  
Resistance Mechanisms ◽  
Present View
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