scholarly journals Plasmid-Mediated Resistance to Thrombin-Induced Platelet Microbicidal Protein in Staphylococci: Role of theqacA Locus

1999 ◽  
Vol 43 (10) ◽  
pp. 2395-2399 ◽  
Author(s):  
Leon Iri Kupferwasser ◽  
Ronald A. Skurray ◽  
Melissa H. Brown ◽  
Neville Firth ◽  
Michael R. Yeaman ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Efflux Pump ◽  
Endothelial Damage ◽  
Cross Resistance ◽  
Cationic Peptide ◽  
Multidrug Resistance Gene ◽  
Phenotypic Resistance ◽  
Platelet Microbicidal Protein

ABSTRACT Thrombin-induced platelet microbicidal protein 1 (tPMP-1) is a small, cationic peptide released from rabbit platelets following thrombin stimulation. In vitro resistance to this peptide among strains of Staphylococcus aureus correlates with the survival advantage of such strains at sites of endothelial damage in humans as well as in experimental endovascular infections. The mechanisms involved in the phenotypic resistance of S. aureus to tPMP-1 are not fully delineated. The plasmid-encoded staphylococcal gene qacA mediates multidrug resistance to multiple organic cations via a proton motive force-dependent efflux pump. We studied whether the qacA gene might also confer resistance to cationic tPMP-1. Staphylococcal plasmids encoding qacA were found to confer resistance to tPMP-1 in an otherwise susceptible parental strain. Deletions which removed the region containing theqacA gene in the S. aureus multiresistance plasmid pSK1 abolished tPMP-1 resistance. Resistance to tPMP-1 in theqacA-bearing strains was inoculum independent but peptide concentration dependent, with the level of resistance decreasing at higher peptide concentrations for a given inoculum. There was no apparent cross-resistance in qacA-bearing strains to other endogenous cationic antimicrobial peptides which are structurally distinct from tPMP-1, including human neutrophil defensin 1, protamine, or the staphylococcal lantibiotics pep5 and nisin. These data demonstrate that the staphylococcal multidrug resistance geneqacA also mediates in vitro resistance to cationic tPMP-1.

scholarly journals Genome-wide analysis of experimentally evolved Candida auris reveals multiple novel mechanisms of multidrug-resistance

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Hans Carolus ◽  
Siebe Pierson ◽  
José F. Mun?oz ◽  
Ana Subotić ◽  
Rita B. Cruz ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Molecular Mechanisms ◽  
Efflux Pump ◽  
Hot Spot ◽  
Chromosome 1 ◽  
Cross Resistance ◽  
Future Research ◽  
Candida Auris ◽  
Genome Wide

Candida auris is globally recognized as an opportunistic fungal pathogen of high concern, due to its extensive multidrug-resistance (MDR). Still, molecular mechanisms of MDR are largely unexplored. This is the first account of genome wide evolution of MDR in C. auris obtained through serial in vitro exposure to azoles, polyenes and echinocandins. We show the stepwise accumulation of multiple novel mutations in genes known and unknown in antifungal drug resistance, albeit almost all new for C. auris. Echinocandin resistance was accompanied by a codon deletion in FKS1hot spot 1 and a substitution in FKS1 ‘novel’ hot spot 3. Mutations in ERG3 and CIS2 further increased the echinocandin MIC. Decreased azole susceptibility was linked to a mutation in transcription factor TAC1b and overexpression of the drug efflux pump Cdr1; a segmental duplication of chromosome 1 containing ERG11; and a whole chromosome 5 duplication, which contains TAC1b. The latter was associated with increased expression of ERG11, TAC1band CDR2, but not CDR1. The simultaneous emergence of nonsense mutations in ERG3 and ERG11 was shown to decrease amphotericin B susceptibility, accompanied with fluconazole cross resistance. A mutation in MEC3, a gene mainly known for its role in DNA damage homeostasis, further increased the polyene MIC. Overall, this study shows the alarming potential and diversity for MDR development in C. auris, even in a clade until now not associated with MDR (clade II),hereby stressing its clinical importance and the urge for future research.

scholarly journals Mutation ofRv2887, amarR-Like Gene, Confers Mycobacterium tuberculosis Resistance to an Imidazopyridine-Based Agent

2015 ◽  
Vol 59 (11) ◽  
pp. 6873-6881 ◽  
Author(s):  
Kathryn Winglee ◽  
Shichun Lun ◽  
Marco Pieroni ◽  
Alan Kozikowski ◽  
William Bishai
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Drug Targets ◽  
Efflux Pump ◽  
Transcriptional Regulator ◽  
Cross Resistance ◽  
Loss Of Function ◽  
Strong Activity ◽  
Content Type ◽  
Novel Drug

ABSTRACTDrug resistance is a major problem inMycobacterium tuberculosiscontrol, and it is critical to identify novel drug targets and new antimycobacterial compounds. We have previously identified an imidazo[1,2-a]pyridine-4-carbonitrile-based agent, MP-III-71, with strong activity againstM. tuberculosis. In this study, we evaluated mechanisms of resistance to MP-III-71. We derived three independentM. tuberculosismutants resistant to MP-III-71 and conducted whole-genome sequencing of these mutants. Loss-of-function mutations inRv2887were common to all three MP-III-71-resistant mutants, and we confirmed the role ofRv2887as a gene required for MP-III-71 susceptibility using complementation. The Rv2887 protein was previously unannotated, but domain and homology analyses suggested it to be a transcriptional regulator in the MarR (multiple antibiotic resistance repressor) family, a group of proteins first identified inEscherichia colito negatively regulate efflux pumps and other mechanisms of multidrug resistance. We found that two efflux pump inhibitors, verapamil and chlorpromazine, potentiate the action of MP-III-71 and that mutation ofRv2887abrogates their activity. We also used transcriptome sequencing (RNA-seq) to identify genes which are differentially expressed in the presence and absence of a functional Rv2887 protein. We found that genes involved in benzoquinone and menaquinone biosynthesis were repressed by functional Rv2887. Thus, inactivating mutations ofRv2887, encoding a putative MarR-like transcriptional regulator, confer resistance to MP-III-71, an effective antimycobacterial compound that shows no cross-resistance to existing antituberculosis drugs. The mechanism of resistance ofM. tuberculosisRv2887mutants may involve efflux pump upregulation and also drug methylation.

scholarly journals In Vitro Activity of the Novel Pleuromutilin Lefamulin (BC-3781) and Effect of Efflux Pump Inactivation on Multidrug-Resistant and Extensively Drug-Resistant Neisseria gonorrhoeae

2017 ◽  
Vol 61 (11) ◽  
Author(s):  
Susanne Jacobsson ◽  
Susanne Paukner ◽  
Daniel Golparian ◽  
Jörgen S. Jensen ◽  
Magnus Unemo
Keyword(s):  
Efflux Pump ◽  
Multidrug Resistant ◽  
Cross Resistance ◽  
Drug Resistant ◽  
The Novel ◽  
Extensively Drug Resistant ◽  
Optimal Dosing ◽  
And Performance ◽  
Reference Strains

ABSTRACT We evaluated the activity of the novel semisynthetic pleuromutilin lefamulin, inhibiting protein synthesis and growth, and the effect of efflux pump inactivation on clinical gonococcal isolates and reference strains (n = 251), including numerous multidrug-resistant and extensively drug-resistant isolates. Lefamulin showed potent activity against all gonococcal isolates, and no significant cross-resistance to other antimicrobials was identified. Further studies of lefamulin are warranted, including in vitro selection and mechanisms of resistance, pharmacokinetics/pharmacodynamics, optimal dosing, and performance in randomized controlled trials.

scholarly journals Reversal of Cancer Multidrug Resistance (MDR) Mediated by ATP-Binding Cassette Transporter G2 (ABCG2) by AZ-628, a RAF Kinase Inhibitor

2020 ◽  
Vol 8 ◽  
Author(s):  
Jing-Quan Wang ◽  
Qiu-Xu Teng ◽  
Zi-Ning Lei ◽  
Ning Ji ◽  
Qingbin Cui ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Kinase Inhibitor ◽  
Efflux Pump ◽  
Simulation Analysis ◽  
Chemotherapeutic Agents ◽  
Dynamics Simulation ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Raf Kinase

Overexpression of ABCG2 remains a major impediment to successful cancer treatment, because ABCG2 functions as an efflux pump of chemotherapeutic agents and causes clinical multidrug resistance (MDR). Therefore, it is important to uncover effective modulators to circumvent ABCG2-mediated MDR in cancers. In this study, we reported that AZ-628, a RAF kinase inhibitor, effectively antagonizes ABCG2-mediated MDR in vitro. Our results showed that AZ-628 completely reversed ABCG2-mediated MDR at a non-toxic concentration (3 μM) without affecting ABCB1-, ABCC1-, or ABCC10 mediated MDR. Further studies revealed that the reversal mechanism was by attenuating ABCG2-mediated efflux and increasing intracellular accumulation of ABCG2 substrate drugs. Moreover, AZ-628 stimulated ABCG2-associated ATPase activity in a concentration-dependent manner. Docking and molecular dynamics simulation analysis showed that AZ-628 binds to the same site as ABCG2 substrate drugs with higher score. Taken together, our studies indicate that AZ-628 could be used in combination chemotherapy against ABCG2-mediated MDR in cancers.

scholarly journals Activities of Newer Fluoroquinolones against Ciprofloxacin-Resistant Streptococcus pneumoniae

2001 ◽  
Vol 45 (6) ◽  
pp. 1654-1659 ◽  
Author(s):  
Elizabeth A. Coyle ◽  
Glenn W. Kaatz ◽  
Michael J. Rybak
Keyword(s):  
Streptococcus Pneumoniae ◽  
Efflux Pump ◽  
Specific Area ◽  
Cross Resistance ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Time Curve ◽  
Ciprofloxacin Resistance ◽  
Derivatives Of

ABSTRACT The incidence of ciprofloxacin resistance in Streptococcus pneumoniae is low but steadily increasing, which raises concerns regarding the clinical impact of potential cross-resistance with newer fluoroquinolones. To investigate this problem, we utilized an in vitro pharmacodynamic model and compared the activities of gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin, and trovafloxacin to that of ciprofloxacin against two laboratory-derived, ciprofloxacin-resistant derivatives of S. pneumoniae (strains R919 and R921). Ciprofloxacin resistance in these strains involved the activity of a multidrug efflux pump and possibly, for R919, a mutation resulting in an amino acid substitution in GyrA. Gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin, and trovafloxacin achieved 99.9% killing of both R919 and R921 in ≤28 h. With respect to levofloxacin, significant regrowth of both mutants was observed at 48 h (P < 0.05). For gatifloxacin, grepafloxacin, moxifloxacin, and trovafloxacin, regrowth was minimal at 48 h, with each maintaining 99.9% killing against both mutants. No killing of either R919 or R921 was observed with exposure to ciprofloxacin. During model experiments, resistance to gatifloxacin, grepafloxacin, moxifloxacin, and trovafloxacin did not develop but the MICs of ciprofloxacin and levofloxacin increased 1 to 2 dilutions for both R919 and R921. Although specific area under the concentration-time curve from 0 to 24 h (AUC0–24)/MIC and maximum concentration of drug in serum (C max)/MIC ratios have not been defined for the fluoroquinolones with respect to gram-positive organisms, our study revealed that significant regrowth and/or resistance was associated with AUC0–24/MIC ratios of ≤31.7 and C max/MIC ratios of ≤3.1. It is evident that the newer fluoroquinolones tested possess improved activity against S. pneumoniae, including strains for which ciprofloxacin MICs were elevated.

Reversal of P-glycoprotein-medicated multidrug resistance by LBM-A5 in vitro and a study of its pharmacokinetics in vivo

2015 ◽  
Vol 93 (1) ◽  
pp. 33-38 ◽  
Author(s):  
Tianxiao Zhao ◽  
Yun Song ◽  
Baomin Liu ◽  
Qianqian Qiu ◽  
Lei Jiao ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Cancer Chemotherapy ◽  
Anticancer Agents ◽  
Efflux Pump ◽  
Therapeutic Index ◽  
Intracellular Accumulation ◽  
P Glycoprotein ◽  
Reversal Mechanism

The overexpression of P-glycoprotein (P-gp) in tumors leads to multidrug resistance (MDR), which is a significant obstacle in clinical cancer chemotherapy. The co-administration of anticancer drugs and MDR modulators is a promising strategy for overcoming this problem. Our study aimed to explore the reversal mechanism and safety of the MDR modulator LBM-A5 in vitro, and evaluate its pharmacokinetics and effects on doxorubicin metabolism in vivo. We evaluated an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of anticancer agents mediated by LBM-A5, the effect of LBM-A5 on rhodamine123 intracellular accumulation, and the efflux in K562/DOX cells to investigate the reversal mechanisms of LBM-A5. The results showed that LBM-A5 inhibits rhodamine123 efflux and increases intracellular accumulation by inhibiting the efflux pump function of P-gp. Furthermore, the therapeutic index and CYP3A4 activity analysis in vitro suggested that LBM-A5 is reasonably safe to use. Also, LBM-A5 (10 mg/kg body mass) achieved the required plasma concentration in sufficient time to reverse MDR in vivo. Importantly, the LBM-A5 treatment group shared similar doxorubicin (DOX) pharmacokinetics with the free DOX group. Our results suggest that LBM-A5 effectively reverses MDR (EC50 = 483.6 ± 81.7 nmol·L−1) by inhibiting the function of P-gp, with relatively ideal pharmacokinetics and in a safe manner, and so may be a promising candidate for cancer chemotherapy research.

scholarly journals Role of the AheABC Efflux Pump in Aeromonas hydrophila Intrinsic Multidrug Resistance

2008 ◽  
Vol 52 (4) ◽  
pp. 1559-1563 ◽  
Author(s):  
Mathieu Hernould ◽  
Séverine Gagné ◽  
Michel Fournier ◽  
Claudine Quentin ◽  
Corinne Arpin
Keyword(s):  
Multidrug Resistance ◽  
Aeromonas Hydrophila ◽  
Efflux Pump ◽  
Gene Inactivation ◽  
Multidrug Efflux ◽  
Intrinsic Resistance

ABSTRACT Gene inactivation and complementation experiments showed that the tripartite AheABC efflux pump of Aeromonas hydrophila extruded at least 13 substrates, including nine antibiotics. The use of phenylalanine-arginine-β-naphthylamide (PAβN) revealed an additional system(s) contributing to intrinsic resistance. This is the first analysis of the role of multidrug efflux systems in Aeromonas spp.

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