scholarly journals Semimechanistic Pharmacokinetic-Pharmacodynamic Model with Adaptation Development for Time-Kill Experiments of Ciprofloxacin against Pseudomonasaeruginosa

2010 ◽  
Vol 54 (6) ◽  
pp. 2379-2384 ◽  
Author(s):  
Nicolas Grégoire ◽  
Sophie Raherison ◽  
Claire Grignon ◽  
Emmanuelle Comets ◽  
Manuella Marliat ◽  
...  
Keyword(s):  
Efflux Pump ◽  
Fold Increase ◽  
Multidrug Efflux ◽  
Multiple Dosing ◽  
Initial Inoculum ◽  
Dosing Regimens ◽  
Moderate Resistance ◽  
Time Kill

ABSTRACT The objective of this study was to implement a semimechanistic pharmacokinetic-pharmacodynamic (PK-PD) model to describe the effects of ciprofloxacin against Pseudomonas aeruginosa in vitro. Time-kill curves were generated with an initial inoculum close to 5 × 106CFU/ml of P. aeruginosa PAO1 and constant ciprofloxacin concentrations between 0.12 and 4.0 μg/ml (corresponding to 0.5× and 16× MIC). To support the model, phenotypic experiments were conducted with the PAO7H mutant strain, which overexpresses the MexEF OprN efflux pump and phenyl arginine β-naphthylamide (PAβN), a known efflux inhibitor of main Mex multidrug efflux systems. A population approach was used for parameter estimation. At subinhibitory ciprofloxacin concentrations (0.12 and 0.25 μg/ml), an initial CFU decay followed by regrowth was observed, attesting to rapid emergence of bacteria with increased but moderate resistance (8-fold increase of MIC). This phenomenon was mainly due to an overexpression of the Mex protein efflux pumps, as shown by a 16-fold diminution of the MIC in the presence of PAβN in these strains with low-level resistance. A PK-PD model with adaptation development was successfully used to describe these data. However, additional experiments are required to validate the robustness of this model after longer exposure periods and multiple dosing regimens, as well as in vivo.

scholarly journals Efficacy of Ampicillin plus Ceftriaxone in Treatment of Experimental Endocarditis Due to Enterococcus faecalis Strains Highly Resistant to Aminoglycosides

1999 ◽  
Vol 43 (3) ◽  
pp. 639-646 ◽  
Author(s):  
Joan Gavaldà ◽  
Carmen Torres ◽  
Carmen Tenorio ◽  
Pedro López ◽  
Myriam Zaragoza ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Enterococcus Faecalis ◽  
Pharmacokinetic Parameters ◽  
Initial Inoculum ◽  
High Level ◽  
Time Kill ◽  
Disk Method ◽  
Level Resistance

The purpose of this work was to evaluate the in vitro possibilities of ampicillin-ceftriaxone combinations for 10 Enterococcus faecalis strains with high-level resistance to aminoglycosides (HLRAg) and to assess the efficacy of ampicillin plus ceftriaxone, both administered with humanlike pharmacokinetics, for the treatment of experimental endocarditis due to HLRAg E. faecalis. A reduction of 1 to 4 dilutions in MICs of ampicillin was obtained when ampicillin was combined with a fixed subinhibitory ceftriaxone concentration of 4 μg/ml. This potentiating effect was also observed by the double disk method with all 10 strains. Time-kill studies performed with 1 and 2 μg of ampicillin alone per ml or in combination with 5, 10, 20, 40, and 60 μg of ceftriaxone per ml showed a ≥2 log10 reduction in CFU per milliliter with respect to ampicillin alone and to the initial inoculum for all 10E. faecalis strains studied. This effect was obtained for seven strains with the combination of 2 μg of ampicillin per ml plus 10 μg of ceftriaxone per ml and for six strains with 5 μg of ceftriaxone per ml. Animals with catheter-induced endocarditis were infected intravenously with 108 CFU of E. faecalis V48 or 105 CFU of E. faecalisV45 and were treated for 3 days with humanlike pharmacokinetics of 2 g of ampicillin every 4 h, alone or combined with 2 g of ceftriaxone every 12 h. The levels in serum and the pharmacokinetic parameters of the humanlike pharmacokinetics of ampicillin or ceftriaxone in rabbits were similar to those found in humans treated with 2 g of ampicillin or ceftriaxone intravenously. Results of the therapy for experimental endocarditis caused by E. faecalis V48 or V45 showed that the residual bacterial titers in aortic valve vegetations were significantly lower in the animals treated with the combinations of ampicillin plus ceftriaxone than in those treated with ampicillin alone (P < 0.001). The combination of ampicillin and ceftriaxone showed in vitro and in vivo synergism against HLRAgE. faecalis.

scholarly journals CmeR Functions as a Pleiotropic Regulator and Is Required for Optimal Colonization of Campylobacter jejuni In Vivo

2008 ◽  
Vol 190 (6) ◽  
pp. 1879-1890 ◽  
Author(s):  
Baoqing Guo ◽  
Ying Wang ◽  
Feng Shi ◽  
Yi-Wen Barton ◽  
Paul Plummer ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Capsular Polysaccharide ◽  
Efflux Pump ◽  
Loss Of Function ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Reverse Transcription Pcr ◽  
Dicarboxylate Transport

ABSTRACT CmeR functions as a transcriptional repressor modulating the expression of the multidrug efflux pump CmeABC in Campylobacter jejuni. To determine if CmeR also regulates other genes in C. jejuni, we compared the transcriptome of the cmeR mutant with that of the wild-type strain using a DNA microarray. This comparison identified 28 genes that showed a ≥2-fold change in expression in the cmeR mutant. Independent real-time quantitative reverse transcription-PCR experiments confirmed 27 of the 28 differentially expressed genes. The CmeR-regulated genes encode membrane transporters, proteins involved in C4-dicarboxylate transport and utilization, enzymes for biosynthesis of capsular polysaccharide, and hypothetical proteins with unknown functions. Among the genes whose expression was upregulated in the cmeR mutant, Cj0561c (encoding a putative periplasmic protein) showed the greatest increase in expression. Subsequent experiments demonstrated that this gene is strongly repressed by CmeR. The presence of the known CmeR-binding site, an inverted repeat of TGTAAT, in the promoter region of Cj0561c suggests that CmeR directly inhibits the transcription of Cj0561c. Similar to expression of cmeABC, transcription of Cj0561c is strongly induced by bile compounds, which are normally present in the intestinal tracts of animals. Inactivation of Cj0561c did not affect the susceptibility of C. jejuni to antimicrobial compounds in vitro but reduced the fitness of C. jejuni in chickens. Loss-of-function mutation of cmeR severely reduced the ability of C. jejuni to colonize chickens. Together, these findings indicate that CmeR governs the expression of multiple genes with diverse functions and is required for Campylobacter adaptation in the chicken host.

Patupilone (epothilone B) inhibits growth and survival of multiple myeloma cells in vitro and in vivo

Blood ◽  
2005 ◽  
Vol 105 (1) ◽  
pp. 350-357 ◽  
Author(s):  
Boris Lin ◽  
Laurence Catley ◽  
Richard LeBlanc ◽  
Constantine Mitsiades ◽  
Renate Burger ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Growth Factor ◽  
Efflux Pump ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Growth And Survival ◽  
Epothilone B ◽  
Endothelial Growth Factor

Abstract In this study, we investigated the in vitro and in vivo efficacy of patupilone (epothilone B, EPO906), a novel nontaxane microtubule stabilizing agent, in treatment of multiple myeloma (MM). Patupilone directly inhibited growth and survival of MM cells, including those resistant to conventional chemotherapies, such as the taxane paclitaxel. Patupilone induced G2M arrest of MM cells, with subsequent apoptosis. Interleukin-6 (IL-6) and insulin-like growth factor-1 (IGF-1), 2 known growth and survival factors for MM, did not protect MM.1S cells against patupilone-induced cell death. Proliferation of MM cells induced by adherence to bone marrow stromal cells (BMSCs) was also inhibited by patupilone and was paralleled by down-regulation of vascular endothelial growth factor (VEGF) secretion. Importantly, stimulation of cells from patients with MM, either with IL-6 or by adherence to BMSCs, enhanced the anti-proliferative and proapoptotic effects of patupilone. Moreover, patupilone was effective against MM cell lines that overexpress the MDR1/P-glycoprotein multidrug efflux pump. In addition, patupilone was effective in slowing tumor growth and prolonging median survival of mice that received orthotopical transplants with MM tumor cells. Taken together, these preclinical findings suggest that patupilone may be a safe and effective drug in the treatment of MM, providing the framework for clinical studies to improve patient outcome in MM. (Blood. 2005;105:350-357)

scholarly journals The Efflux Pump Inhibitor Timcodar Improves the Potency of Antimycobacterial Agents

2014 ◽  
Vol 59 (3) ◽  
pp. 1534-1541 ◽  
Author(s):  
Trudy H. Grossman ◽  
Carolyn M. Shoen ◽  
Steven M. Jones ◽  
Peter L. Jones ◽  
Michael H. Cynamon ◽  
...  
Keyword(s):  
Mouse Model ◽  
Efflux Pump ◽  
Fold Increase ◽  
Broth Culture ◽  
Efflux Pump Inhibitor ◽  
Content Type ◽  
Combination Studies ◽  
Drug Dependent

ABSTRACTPrevious studies indicated that inhibition of efflux pumps augments tuberculosis therapy. In this study, we used timcodar (formerly VX-853) to determine if this efflux pump inhibitor could increase the potency of antituberculosis (anti-TB) drugs againstMycobacterium tuberculosisinin vitroandin vivocombination studies. When used alone, timcodar weakly inhibitedM. tuberculosisgrowth in broth culture (MIC, 19 μg/ml); however, it demonstrated synergism in drug combination studies with rifampin, bedaquiline, and clofazimine but not with other anti-TB agents. WhenM. tuberculosiswas cultured in host macrophage cells, timcodar had about a 10-fold increase (50% inhibitory concentration, 1.9 μg/ml) in the growth inhibition ofM. tuberculosisand demonstrated synergy with rifampin, moxifloxacin, and bedaquiline. In a mouse model of tuberculosis lung infection, timcodar potentiated the efficacies of rifampin and isoniazid, conferring 1.0 and 0.4 log10reductions in bacterial burden in lung, respectively, compared to the efficacy of each drug alone. Furthermore, timcodar reduced the likelihood of a relapse infection when evaluated in a mouse model of long-term, chronic infection with treatment with a combination of rifampin, isoniazid, and timcodar. Although timcodar had no effect on the pharmacokinetics of rifampin in plasma and lung, it did increase the plasma exposure of bedaquiline. These data suggest that the antimycobacterial drug-potentiating activity of timcodar is complex and drug dependent and involves both bacterial and host-targeted mechanisms. Further study of the improvement of the potency of antimycobacterial drugs and drug candidates when used in combination with timcodar is warranted.

scholarly journals Lincomycin Resistance Mutations in Two Regions Immediately Downstream of the −10 Region of lmr Promoter Cause Overexpression of a Putative Multidrug Efflux Pump in Bacillus subtilis Mutants

2003 ◽  
Vol 47 (1) ◽  
pp. 432-435 ◽  
Author(s):  
Miyuki Kumano ◽  
Masaya Fujita ◽  
Kouji Nakamura ◽  
Makiko Murata ◽  
Reiko Ohki ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Efflux Pump ◽  
Resistance Mutations ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Lincomycin Resistance

ABSTRACT We isolated 19 lincomycin-resistant Bacillus subtilis mutants by expressing lmrB encoding a putative multidrug efflux protein. Eighteen of the mutants altered at two regions (−3 to −1 and +15) immediately downstream of the −10 region of the lmr promoter increased lmr transcription in vivo and in vitro.

scholarly journals Low-Level Resistance of Staphylococcus aureus to Thrombin-Induced Platelet Microbicidal Protein 1 In Vitro Associated with qacA Gene Carriage Is Independent of Multidrug Efflux Pump Activity

2006 ◽  
Vol 50 (7) ◽  
pp. 2448-2454 ◽  
Author(s):  
A. S. Bayer ◽  
L. I. Kupferwasser ◽  
M. H. Brown ◽  
R. A. Skurray ◽  
S. Grkovic ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cytoplasmic Membrane ◽  
Efflux Pump ◽  
Multidrug Transporter ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Pump Activity ◽  
The Impact

ABSTRACT Thrombin-induced platelet microbial protein 1 (tPMP-1), a cationic antimicrobial polypeptide released from thrombin-stimulated rabbit platelets, targets the Staphylococcus aureus cytoplasmic membrane to initiate its microbicidal effects. In vitro resistance to tPMP-1 correlates with survival advantages in vivo. In S. aureus, the plasmid-carried qacA gene encodes a multidrug transporter, conferring resistance to organic cations (e.g., ethidium [Et]) via proton motive force (PMF)-energized export. We previously showed that qacA also confers a tPMP-1-resistant (tPMP-1r) phenotype in vitro. The current study evaluated whether (i) transporters encoded by the qacB and qacC multidrug resistance genes also confer tPMP-1r and (ii) tPMP-1r mediated by qacA is dependent on efflux pump activity. In contrast to tPMP-1r qacA-bearing strains, the parental strain and its isogenic qacB- and qacC-containing strains were tPMP-1 susceptible (tPMP-1s). Efflux pump inhibition by cyanide m-chlorophenylhydrazone abrogated Etr, but not tPMP-1r, in the qacA-bearing strain. In synergy assays, exposure of the qacA-bearing strain to tPMP-1 did not affect the susceptibility of Et (ruling out Et-tPMP-1 cotransport). The following cytoplasmic membrane parameters did not differ significantly between the qacA-bearing and parental strains: contents of the major phospholipids; asymmetric distributions of the positively charged species, lysyl-phosphotidylglycerol; fatty acid composition; and relative surface charge. Of note, the qacA-bearing strain exhibited greater membrane fluidity than that of the parental, qacB-, or qacC-bearing strain. In conclusion, among these families of efflux pumps, only the multidrug transporter encoded by qacA conferred a tPMP-1r phenotype. These data suggest that qacA-encoded tPMP-1r results from the impact of a specific transporter upon membrane structure or function unrelated to PMF-dependent peptide efflux.

scholarly journals Critical Role of Multidrug Efflux Pump CmeABC in Bile Resistance and In Vivo Colonization of Campylobacter jejuni

2003 ◽  
Vol 71 (8) ◽  
pp. 4250-4259 ◽  
Author(s):  
Jun Lin ◽  
Orhan Sahin ◽  
Linda Overbye Michel ◽  
Qijing Zhang
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Efflux Pump ◽  
In Vitro Growth ◽  
Wild Type ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Bile Resistance

ABSTRACT CmeABC functions as a multidrug efflux pump contributing to the resistance of Campylobacter to a broad range of antimicrobials. In this study, we examined the role of CmeABC in bile resistance and its contribution to the adaptation of Campylobacter jejuni in the intestinal tract of the chicken, a natural host and a major reservoir for Campylobacter. Inactivation of cmeABC drastically decreased the resistance of Campylobacter to various bile salts. Addition of choleate (2 mM) in culture medium impaired the in vitro growth of the cmeABC mutants but had no effect on the growth of the wild-type strain. Bile concentration varied in the duodenum, jejunum, and cecum of chicken intestine, and the inhibitory effect of the intestinal extracts on the in vitro growth of Campylobacter was well correlated with the total bile concentration in the individual sections of chicken intestine. When inoculated into chickens, the wild-type strain colonized the birds as early as day 2 postinoculation with a density as high as 107 CFU/g of feces. In contrast, the cmeABC mutants failed to colonize any of the inoculated chickens throughout the study. The minimum infective dose for the cmeABC mutant was at least 2.6 × 104-fold higher than that of the wild-type strain. Complementation of the cmeABC mutants with a wild-type cmeABC allele in trans fully restored the in vitro growth in bile-containing media and the in vivo colonization to the levels of the wild-type strain. Immunoblotting analysis indicated that CmeABC is expressed and immunogenic in chickens experimentally infected with C. jejuni. Together, these findings provide compelling evidence that CmeABC, by mediating resistance to bile salts in the intestinal tract, is required for successful colonization of C. jejuni in chickens. Inhibition of CmeABC function may not only control antibiotic resistance but also prevent the in vivo colonization of pathogenic Campylobacter.

scholarly journals Restoring colistin sensitivity in colistin-resistant E. coli: Combinatorial use of MarR inhibitor with efflux pump inhibitor

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Niranjana Sri Sundaramoorthy ◽  
Pavithira Suresh ◽  
Subramaniapillai Selva Ganesan ◽  
ArunKumar GaneshPrasad ◽  
Saisubramanian Nagarajan
Keyword(s):  
Muscle Tissue ◽  
Efflux Pump ◽  
Efflux Pump Inhibitor ◽  
E Coli ◽  
Log Reduction ◽  
Cell Counts ◽  
Highly Effective ◽  
Time Kill

AbstractAntibiotics like colistin are the last resort to deal with infections by carbapenem-resistant Enterobacteriaceae (CREB). Resistance to colistin severely restricts therapeutic options. To tackle this dire situation, urgent measures to restore colistin sensitivity are needed. In this study, whole-genome sequencing of colistin-resistant E. coli strain was performed and the genome analysis revealed that the strain belonged to the sequence type ST405. Multiple mutations were observed in genes implicated in colistin resistance, especially those related to the L-Ara-4-N pathway but mgrB was unmutated and mcr1-9 genes were missing. MarR inhibitor salicylate was used to re-sensitize this strain to colistin, which increased the negative charge on the cell surface especially in colistin resistant E. coli (U3790 strain) and thereby facilitated a decrease in colistin MIC by 8 fold. It is indeed well known that MarR inhibition by salicylate triggers the expression of AcrAB efflux pumps through MarA. So, in order to fully restore colistin sensitivity, a potent efflux pump inhibitor (BC1), identified earlier by this group was employed. The combination of colistin with both salicylate and BC1 caused a remarkable 6 log reduction in cell counts of U3790 in time-kill assay. Infection of muscle tissue of zebrafish with U3790 followed by various treatments showed that the combination of colistin + salicylate + BC1 was highly effective in reducing bioburden in infected muscle tissue by 4 log fold. Thus, our study shows that a combination of MarR inhibitor to enhance colistin binding and efflux pump inhibitor to reduce colistin extrusion was highly effective in restoring colistin sensitivity in colistin-resistant clinical isolate of E. coli in vitro and in vivo.

scholarly journals Fungicidal Synergism of Fluconazole and Cyclosporine in Candida albicans Is Not Dependent on Multidrug Efflux Transporters Encoded by the CDR1, CDR2, CaMDR1, and FLU1 Genes

2003 ◽  
Vol 47 (5) ◽  
pp. 1565-1570 ◽  
Author(s):  
Oscar Marchetti ◽  
Philippe Moreillon ◽  
Josè M. Entenza ◽  
Jacques Vouillamoz ◽  
Michel P. Glauser ◽  
...  
Keyword(s):  
Efflux Pump ◽  
Day Treatment ◽  
Efflux Transporters ◽  
High Dose ◽  
Multidrug Efflux ◽  
Cellular Targets ◽  
Fungicidal Effect ◽  
In Vivo Experiments

ABSTRACT The combination of fluconazole (FLC) and cyclosporine (CY) is fungicidal in FLC-susceptible C. albicans (O. Marchetti, P. Moreillon, M. P. Glauser, J. Bille, and D. Sanglard, Antimicrob. Agents Chemother. 44:2373-2381, 2000). The mechanism of this synergism is unknown. CY has several cellular targets including multidrug efflux transporters. The hypothesis that CY might inhibit FLC efflux was investigated by comparing the effect of FLC-CY in FLC-susceptible parent CAF2-1 (FLC MIC, 0.25 mg/liter) and in FLC-hypersusceptible mutant DSY1024 (FLC MIC, 0.03 mg/liter), in which the CDR1, CDR2, CaMDR1, and FLU1 transporter genes have been selectively deleted. We postulated that a loss of the fungicidal effect of FLC-CY in DSY1024 would confirm the roles of these efflux pumps. Time-kill curve studies showed a more potent fungistatic effect of FLC (P = 0.05 at 48 h with an inoculum of 103 CFU/ml) and a more rapid fungicidal effect of FLC-CY (P = 0.05 at 24 h with an inoculum of 103 CFU/ml) in the FLC-hypersusceptible mutant compared to those in the parent. Rats with experimental endocarditis were treated for 2 or 5 days with high-dose FLC, high-dose CY, or both drugs combined. FLC monotherapy for 5 days was more effective against the hypersusceptible mutant than against the parent. However, the addition of CY to FLC still conferred a therapeutic advantage in animals infected with mutant DSY1024, as indicated by better survival (P = 0.04 versus the results obtained with FLC) and sterilization of valves and kidneys after a very short (2-day) treatment (P = 0.009 and 0.002, respectively, versus the results obtained with FLC). Both in vitro and in vivo experiments consistently showed that the deletion of the four membrane transporters in DSY1024 did not result in loss of the fungicidal effect of FLC-CY. Yet, the accelerated killing in the mutant suggested a “dual-hit” mechanism involving FLC hypersusceptibility due to the efflux pump elimination and fungicidal activity conferred by CY. Thus, inhibition of multidrug efflux transporters encoded by CDR1, CDR2, CaMDR1, and FLU1 genes is not responsible for the fungicidal synergism of FLC-CY. Other cellular targets must be considered.

A new PKPD model to characterize the inoculum effect of Acinetobacter baumannii on polymyxin B in vitro

2021 ◽  
Author(s):  
Grace Akrong ◽  
Alexia Chauzy ◽  
Vincent Aranzana-Climent ◽  
Mathilde Lacroix ◽  
Luc Deroche ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Fold Increase ◽  
Polymyxin B ◽  
Inoculum Size ◽  
Adaptive Resistance ◽  
Pkpd Model ◽  
Inoculum Effect ◽  
Time Kill

The inoculum effect (i.e., reduction in antimicrobial activity at large starting inoculum) is a phenomenon described for various pathogens. Since limited data exist regarding inoculum effect of Acinetobacter baumannii , we evaluated killing of A. baumannii by polymyxin B, a last-resort antibiotic, at several starting inocula and developed a PKPD model to capture this phenomenon. In vitro static time-kill experiments were performed using polymyxin B at concentrations ranging from 0.125 to 128 mg/L against a clinical A. baumannii isolate at four starting inocula from 10 5 to 10 8 CFU/mL. Samples were collected up to 30 h to quantify the viable bacterial burden and were simultaneously modeled in the NONMEM software program. The expression of polymyxin B resistance genes ( lpxACD , pmrCAB and wzc ), and genetic modifications were studied by RT-qPCR and DNA sequencing experiments, respectively. The PKPD model included a single homogeneous bacterial population with adaptive resistance. Polymyxin B effect was modelled as a sigmoidal E max model and the inoculum effect as an increase of polymyxin B EC 50 with increasing starting inoculum using a power function. Polymyxin B displayed a reduced activity as the starting inoculum increased: a 20-fold increase of polymyxin B EC 50 was observed between the lowest and the highest inoculum. No effects of polymyxin B and inoculum size were observed on the studied genes. The proposed PKPD model successfully described and predicted the pronounced in vitro inoculum effect of A. baumannii on polymyxin B activity. These results should be further validated using other bacteria/antibiotic combinations and in vivo models.

Sign in / Sign up

Export Citation Format

Share Document