scholarly journals Bacterial Mixology: Combining Pharmacodynamic Models to Predict In Vitro Competition of MCR-1-Harboring E. coli

Antibiotics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Nicholas M. Smith ◽  
Arthur Chan ◽  
Thomas D. Nguyen ◽  
Jacob T. Dumbleton
Keyword(s):  
Total Population ◽  
Selective Pressure ◽  
A Priori ◽  
Polymyxin B ◽  
Colistin Resistance ◽  
High Concentration ◽  
Bacterial Killing ◽  
E Coli ◽  
Selection Of

The emergence of mobile colistin resistance (mcr)-mediated polymyxin resistance has resulted in a significant detriment to the utility of the polymyxins in the clinical setting. Though the risk for horizontal transfer of an mcr-containing plasmid is a major component of the transmissibility, selection of polymyxin resistant subpopulations is still a major risk factor for developing polymyxin-resistant infections. Using static time-kills over 24 h (h), we performed competition studies by mixing known inocula of isogenic Escherichia coli strains (wildtype [WT] and mcr-1-harboring) and treating with a concentration array of polymyxin B. These results were then compared to a priori predictions of bacterial-killing effects by polymyxin B on a mixed population of E. coli cells using a previously published mechanism-based model. The data showed that both selective pressure between WT and mcr-1-harboring strains as well as underlying polymyxin B heteroresistance within each of the two strains contributed to bacterial regrowth despite treatment with high concentration polymyxin B. Moreover, the simulations showed that when mcr-1-harboring cells were 1% or 10% of the total population, regrowth by 24 h was still observed in ≥50% of the simulated subjects for both a 106 and 108 inoculum. These results indicate that at lower inoculums with a low proportion of mcr-1-harboring cells, selective pressure from a pharmacokinetic-optimized regimen of polymyxin B still results in regrowth and selection of polymyxin-resistant cells.

The Effects of Shock Vancomycin Concentrations on the Formation of Heteroresistance in Staphylococcus aureus

2020 ◽  
Vol 65 (9-10) ◽  
pp. 3-7
Author(s):  
V. V. Gostev ◽  
Yu. V. Sopova ◽  
O. S. Kalinogorskaya ◽  
M. E. Velizhanina ◽  
I. V. Lazareva ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
In Vitro Selection ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
High Concentration ◽  
Short Term ◽  
High Concentrations ◽  
Selection Of ◽  
Selection Of Resistance ◽  
Test Cultures

Glycopeptides are the basis of the treatment of infections caused by MRSA (Methicillin-Resistant Staphylococcus aureus). Previously, it was demonstrated that antibiotic tolerant phenotypes are formed during selection of resistance under the influence of high concentrations of antibiotics. The present study uses a similar in vitro selection model with vancomycin. Clinical isolates of MRSA belonging to genetic lines ST8 and ST239, as well as the MSSA (ATCC29213) strain, were included in the experiment. Test isolates were incubated for five hours in a medium with a high concentration of vancomycin (50 μg/ml). Test cultures were grown on the medium without antibiotic for 18 hours after each exposure. A total of ten exposure cycles were performed. Vancomycin was characterized by bacteriostatic action; the proportion of surviving cells after exposure was 70–100%. After selection, there was a slight increase in the MIC to vancomycin (MIC 2 μg/ml), teicoplanin (MIC 1.5–3 μg/ml) and daptomycin (MIC 0.25–2 μg/ml). According to the results of PAP analysis, all strains showed an increase in the area under curve depending on the concentration of vancomycin after selection, while a heteroresistant phenotype (with PAP/AUC 0.9) was detected in three isolates. All isolates showed walK mutations (T188S, D235N, E261V, V380I, and G223D). Exposure to short-term shock concentrations of vancomycin promotes the formation of heteroresistance in both MRSA and MSSA. Formation of VISA phenotypes is possible during therapy with vancomycin.

scholarly journals Streptococcus pneumoniae DNA Gyrase and Topoisomerase IV: Overexpression, Purification, and Differential Inhibition by Fluoroquinolones

1999 ◽  
Vol 43 (5) ◽  
pp. 1129-1136 ◽  
Author(s):  
Xiao-Su Pan ◽  
L. Mark Fisher
Keyword(s):  
Streptococcus Pneumoniae ◽  
Dna Gyrase ◽  
Dna Supercoiling ◽  
Topoisomerase Iv ◽  
T7 Promoter ◽  
Bacterial Killing ◽  
E Coli ◽  
Apparent Homogeneity ◽  
Comparable Activity

ABSTRACT Streptococcus pneumoniae gyrA and gyrBgenes specifying the DNA gyrase subunits have been cloned into pET plasmid vectors under the control of an inducible T7 promoter and have been separately expressed in Escherichia coli. Soluble 97-kDa GyrA and 72-kDa GyrB proteins bearing polyhistidine tags at their respective C-terminal and N-terminal ends were purified to apparent homogeneity by one-step nickel chelate column chromatography and were free of host E. coli topoisomerase activity. Equimolar amounts of the gyrase subunits reconstituted ATP-dependent DNA supercoiling with comparable activity to gyrase of E. coli and Staphylococcus aureus. In parallel, S. pneumoniae topoisomerase IV ParC and ParE subunits were similarly expressed in E. coli, purified to near homogeneity as 93- and 73-kDa proteins, and shown to generate efficient ATP-dependent DNA relaxation and DNA decatenation activities. Using the purified enzymes, we examined the inhibitory effects of three paradigm fluoroquinolones—ciprofloxacin, sparfloxacin, and clinafloxacin—which previous genetic studies with S. pneumoniae suggested act preferentially through topoisomerase IV, through gyrase, and through both enzymes, respectively. Surprisingly, all three quinolones were more active in inhibiting purified topoisomerase IV than gyrase, with clinafloxacin showing the greatest inhibitory potency. Moreover, the tested agents were at least 25-fold more effective in stabilizing a cleavable complex (the relevant cytotoxic lesion) with topoisomerase IV than with gyrase, with clinafloxacin some 10- to 32-fold more potent against either enzyme, in line with its superior activity againstS. pneumoniae. The uniform target preference of the three fluoroquinolones for topoisomerase IV in vitro is in apparent contrast to the genetic data. We interpret these results in terms of a model for bacterial killing by quinolones in which cellular factors can modulate the effects of target affinity to determine the cytotoxic pathway.

scholarly journals In VivoTransmission of an IncA/C Plasmid in Escherichia coli Depends on Tetracycline Concentration, and Acquisition of the Plasmid Results in a Variable Cost of Fitness

2015 ◽  
Vol 81 (10) ◽  
pp. 3561-3570 ◽  
Author(s):  
Timothy J. Johnson ◽  
Randall S. Singer ◽  
Richard E. Isaacson ◽  
Jessica L. Danzeisen ◽  
Kevin Lang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
High Dose ◽  
Broad Host Range ◽  
Antibiotic Administration ◽  
Dose Administration ◽  
Content Type ◽  
E Coli ◽  
The Impact ◽  
Selection Of

ABSTRACTIncA/C plasmids are broad-host-range plasmids enabling multidrug resistance that have emerged worldwide among bacterial pathogens of humans and animals. Although antibiotic usage is suspected to be a driving force in the emergence of such strains, few studies have examined the impact of different types of antibiotic administration on the selection of plasmid-containing multidrug resistant isolates. In this study, chlortetracycline treatment at different concentrations in pig feed was examined for its impact on selection and dissemination of an IncA/C plasmid introduced orally via a commensalEscherichia colihost. Continuous low-dose administration of chlortetracycline at 50 g per ton had no observable impact on the proportions of IncA/C plasmid-containingE. colifrom pig feces over the course of 35 days. In contrast, high-dose administration of chlortetracycline at 350 g per ton significantly increased IncA/C plasmid-containingE. coliin pig feces (P< 0.001) and increased movement of the IncA/C plasmid to other indigenousE. colihosts. There was no evidence of conjugal transfer of the IncA/C plasmid to bacterial species other thanE. coli.In vitrocompetition assays demonstrated that bacterial host background substantially impacted the cost of IncA/C plasmid carriage inE. coliandSalmonella.In vitrotransfer and selection experiments demonstrated that tetracycline at 32 μg/ml was necessary to enhance IncA/C plasmid conjugative transfer, while subinhibitory concentrations of tetracyclinein vitrostrongly selected for IncA/C plasmid-containingE. coli. Together, these experiments improve our knowledge on the impact of differing concentrations of tetracycline on the selection of IncA/C-type plasmids.

scholarly journals Once-daily gentamicin therapy for experimental Escherichia coli meningitis.

1997 ◽  
Vol 41 (1) ◽  
pp. 49-53 ◽  
Author(s):  
A Ahmed ◽  
M M París ◽  
M Trujillo ◽  
S M Hickey ◽  
L Wubbel ◽  
...  
Keyword(s):  
In Vivo Studies ◽  
Bacterial Killing ◽  
Once Daily ◽  
E Coli ◽  
Aminoglycoside Therapy ◽  
Gentamicin Concentration ◽  
Gentamicin Therapy ◽  
The Impact

In vitro and in vivo studies have demonstrated that the bacteriologic efficacy of once-daily aminoglycoside therapy is equivalent to that achieved with conventional multiple daily dosing. The impact of once-daily dosing for meningitis has not been studied. Using the well-characterized rabbit meningitis model, we compared two regimens of the same daily dosage of gentamicin given either once or in three divided doses for 24 or 72 h. The initial 1 h mean cerebrospinal fluid (CSF) gentamicin concentration for animals receiving a single dose (2.9 +/- 1.7 micrograms/ml) was threefold higher than that for the animals receiving multiple doses. The rate of bacterial killing in the first 8 h of treatment was significantly greater for the animals with higher concentrations in their CSF (-0.21 +/- 0.19 versus -0.03 +/- 0.22 log10 CFU/ml/h), suggesting concentration-dependent killing. By 24h, the mean reduction in bacterial titers was similar for the two regimens. In animals treated for 72 h, no differences in bactericidal activity was noted for 24, 48, or 72 h. Gentamicin at two different dosages was administered intracisternally to a separate set of animals to achieve considerably higher CSF gentamicin concentrations. In these animals, the rate of bacterial clearance in the first 8 h (0.52 +/- 0.15 and 0.58 +/- 0.15 log10 CFU/ml/h for the lower and higher dosages, respectively) was significantly greater than that in animals treated intravenously. In conclusion, there is evidence of concentration-dependent killing with gentamicin early in treatment for experimental E. coli meningitis, and once-daily dosing therapy appears to be at least as effective as multiple-dose therapy in reducing bacterial counts in CSF.

scholarly journals Polymyxin Triple Combinations against Polymyxin-Resistant, Multidrug-Resistant, KPC-Producing Klebsiella pneumoniae

2020 ◽  
Vol 64 (8) ◽  
Author(s):  
Su Mon Aye ◽  
Irene Galani ◽  
Heidi Yu ◽  
Jiping Wang ◽  
Ke Chen ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Triple Therapy ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Infection Model ◽  
Bacterial Killing ◽  
Standard Dosage ◽  
Time Kill

ABSTRACT Resistance to polymyxin antibiotics is increasing. Without new antibiotic classes, combination therapy is often required. We systematically investigated bacterial killing with polymyxin-based combinations against multidrug-resistant (including polymyxin-resistant), carbapenemase-producing Klebsiella pneumoniae. Monotherapies and double- and triple-combination therapies were compared to identify the most efficacious treatment using static time-kill studies (24 h, six isolates), an in vitro pharmacokinetic/pharmacodynamic model (IVM; 48 h, two isolates), and the mouse thigh infection model (24 h, six isolates). In static time-kill studies, all monotherapies (polymyxin B, rifampin, amikacin, meropenem, or minocycline) were ineffective. Initial bacterial killing was enhanced with various polymyxin B-containing double combinations; however, substantial regrowth occurred in most cases by 24 h. Most polymyxin B-containing triple combinations provided greater and more sustained killing than double combinations. Standard dosage regimens of polymyxin B (2.5 mg/kg of body weight/day), rifampin (600 mg every 12 h), and amikacin (7.5 mg/kg every 12 h) were simulated in the IVM. Against isolate ATH 16, no viable bacteria were detected across 5 to 25 h with triple therapy, with regrowth to ∼2-log10 CFU/ml occurring at 48 h. Against isolate BD 32, rapid initial killing of ∼3.5-log10 CFU/ml at 5 h was followed by a slow decline to ∼2-log10 CFU/ml at 48 h. In infected mice, polymyxin B monotherapy (60 mg/kg/day) generally was ineffective. With triple therapy (polymyxin B at 60 mg/kg/day, rifampin at 120 mg/kg/day, and amikacin at 300 mg/kg/day), at 24 h there was an ∼1.7-log10 CFU/thigh reduction compared to the starting inoculum for all six isolates. Our results demonstrate that the polymyxin B-rifampin-amikacin combination significantly enhanced in vitro and in vivo bacterial killing, providing important information for the optimization of polymyxin-based combinations in patients.

scholarly journals Pharmacodynamics and Bactericidal Activity of Moxifloxacin in Experimental Escherichia coliMeningitis

2001 ◽  
Vol 45 (11) ◽  
pp. 3092-3097 ◽  
Author(s):  
Violeta Rodriguez-Cerrato ◽  
Cynthia C. McCoig ◽  
Ian C. Michelow ◽  
Faryal Ghaffar ◽  
Hasan S. Jafri ◽  
...  
Keyword(s):  
Bactericidal Activity ◽  
Rabbit Model ◽  
Time Curve ◽  
Bacterial Killing ◽  
E Coli ◽  
Pharmacodynamic Profile ◽  
Spectrum Activity ◽  
Csf Concentration ◽  
Broad Spectrum Activity

ABSTRACT Moxifloxacin, an 8-methoxyquinolone with broad-spectrum activity in vitro, was studied in the rabbit model of Escherichia colimeningitis. The purposes of this study were to evaluate the bactericidal effectiveness and the pharmacodynamic profile of moxifloxacin in cerebrospinal fluid (CSF) and to compare the bactericidal activity with that of ceftriaxone and meropenem therapy. After induction of meningitis, animals were given single doses of 10, 20, and 40 mg/kg or divided-dose regimens of 5, 10, and 20 mg/kg twice, separated by 6 h. After single doses, the penetration of moxifloxacin into purulent CSF, measured as percentage of the area under the concentration-time curve (AUC) in CSF relative to the AUC in plasma, was approximately 50%. After single doses of 10, 20, and 40 mg/kg, the maximum CSF concentration (C max) values were 1.8, 4.2, and 4.9 μg/ml, respectively; the AUC values (total drug) were 13.4, 25.4, and 27.1 μg/ml · h, respectively, and the half-life values (t ½) were 6.7, 6.6, and 4.7 h, respectively. The bacterial killing in CSF for moxifloxacin, calculated as the Δlog10 CFU per milliliter per hour, at 3, 6, and 12 h after single doses of 10, 20, and 40 mg/kg were −5.70, −6.62, and −7.02; −7.37, −7.37, and −6.87; and −6.62, −6.62, and −6.62, respectively, whereas those of ceftriaxone and meropenem were −4.18, −5.24, and −4.43, and −3.64, −3.59, and −4.12, respectively. The CSF pharmacodynamic indices of AUC/MBC and C max/MBC were interrelated (r = 0.81); there was less correlation withT > MBC (r = 0.74). In this model, therapy with moxifloxacin appears to be at least as effective as ceftriaxone and more effective than meropenem therapy in eradicatingE. coli from CSF.

scholarly journals Mechanistic Insights into Crosstalk of Tet(X) and MCR-1, Two Resistance Enzymes Co-produced by A Single Plasmid

2020 ◽  
Author(s):  
Yongchang Xu ◽  
Lizhang Liu ◽  
Huimin Zhang ◽  
Youjun Feng
Keyword(s):  
Resistance Gene ◽  
Infection Model ◽  
Global Public Health ◽  
Genetic Determinants ◽  
Colistin Resistance ◽  
E Coli ◽  
New Variant ◽  
Single Plasmid

AbstractTigecycline and colistin are few of last-resort defenses used in anti-infection therapies against carbapenem-resistant bacterial pathogens. The successive emergence of plasmid-borne tet(X) tigecycline resistance mechanism and mobile colistin resistance (mcr) determinant, renders them clinically ineffective, posing a risky challenge to global public health. Here, we report that co-carriage of tet(X6) and mcr-1 gives co-resistance to both classes of antibiotics by a single plasmid in E. coli. Genomic analysis suggested that transposal transfer of mcr-1 proceeds into the plasmid pMS8345A, in which a new variant tet(X6) is neighbored with Class I integron. The structure-guided mutagenesis finely revealed the genetic determinants of Tet(X6) in the context of phenotypic tigecycline resistance. The combined evidence in vitro and in vivo demonstrated its enzymatic action of Tet(X6) in the destruction of tigecycline. The presence of Tet(X6) (and/or MCR-1) robustly prevents the accumulation of reactive oxygen species (ROS) induced by tigecycline (and/or colistin). Unlike that mcr-1 exerts fitness cost in E. coli, tet(X6) does not. In the tet(X6)-positive strain that co-harbors mcr-1, tigecycline resistance is independently of colistin resistance caused by MCR-1-mediated lipid A remodeling, and vice versa. Co-production of Tet(X6) and MCR-1 gives no synergistic delayed growth of the recipient E. coli. Similar to that MCR-1 behaves in the infection model of G. mellonella, Tet(X6) renders the treatment of tigecycline ineffective. Therefore, co-transfer of such two AMR genes is of great concern in the context of “one health” comprising environmental/animal/human sectors, and heightened efforts are required to monitor its dissemination.Author summaryWe report that tet(X6), a new tigecycline resistance gene, is co-carried with the other resistance gene mcr-1 by a single plasmid. Not only have we finely mapped genetic determinants of tet(X6), but also revealed its biochemical action of tigecycline destruction. Crosstalk of Tet(X6) with MCR-1 is addressed. Tet(X6) tigecycline resistance is independently of MCR-1 colistin resistance, and vice versa. Similar to MCR-1 that renders colistin clinically ineffective, Tet(X6) leads to the failure of tigecycline treatment in the infection model of G. mellonella. This study extends mechanistic understanding mechanism and interplay of Tet(X6) and MCR-1, coproduced by a single plasmid. It also heightens the need to prevent rapid and large-scaled spread of AMR.

scholarly journals Quercetin Rejuvenates Sensitization of Colistin-Resistant Escherichia coli and Klebsiella Pneumoniae Clinical Isolates to Colistin

2021 ◽  
Vol 9 ◽  
Author(s):  
Yishuai Lin ◽  
Ying Zhang ◽  
Shixing Liu ◽  
Dandan Ye ◽  
Liqiong Chen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Alternative Pathway ◽  
Membrane Damage ◽  
New Drugs ◽  
Colistin Resistance ◽  
Cell Membrane Damage ◽  
E Coli

Colistin is being considered as “the last ditch” treatment in many infections caused by Gram-negative stains. However, colistin is becoming increasingly invalid in treating patients who are infected with colistin-resistant Escherichia coli (E. coli) and Klebsiella Pneumoniae (K. pneumoniae). To cope with the continuous emergence of colistin resistance, the development of new drugs and therapies is highly imminent. Herein, in this work, we surprisingly found that the combination of quercetin with colistin could efficiently and synergistically eradicate the colistin-resistant E. coli and K. pneumoniae, as confirmed by the synergy checkboard and time-kill assay. Mechanismly, the treatment of quercetin combined with colistin could significantly downregulate the expression of mcr-1 and mgrB that are responsible for colistin-resistance, synergistically enhancing the bacterial cell membrane damage efficacy of colistin. The colistin/quercetin combination was notably efficient in eradicating the colistin-resistant E. coli and K. pneumoniae both in vitro and in vivo. Therefore, our results may provide an efficient alternative pathway against colistin-resistant E. coli and K. pneumoniae infections.

scholarly journals Interactions of polymyxin B in combination with aztreonam, minocycline, meropenem and rifampicin against Escherichia coli producing NDM and OXA-48-group carbapenemases

2021 ◽  
Author(s):  
Anna Olsson ◽  
Marcus Hong ◽  
Hissa Al-Farsi ◽  
Christian G. Giske ◽  
Pernilla Lagerbäck ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Lipid A ◽  
Time Lapse ◽  
Polymyxin B ◽  
Positive Interactions ◽  
Exact Test ◽  
E Coli ◽  
Genes Encoding ◽  
Severe Infections

Objectives. Carbapenemase-producing Enterobacterales pose an increasing medical threat. Combination therapy is often used for severe infections; however, there is little evidence supporting the optimal selection of drugs. This study aimed to determine the in vitro effects of polymyxin B combinations against carbapenemase-producing Escherichia coli . Methods. The interactions of polymyxin B in combination with aztreonam, meropenem, minocycline or rifampicin against 20 clinical isolates of NDM and OXA-48-group-producing E. coli were evaluated using time-lapse microscopy. 24-h samples were spotted on plates with and without 4 x MIC polymyxin B for viable counts. Whole-genome sequencing was applied to identify resistance genes and mutations. Finally, potential associations between combination effects and bacterial genotypes were assessed using Fisher’s exact test. Results. Synergistic and bactericidal effects were observed with polymyxin B and minocycline against 11/20 strains and with polymyxin B and rifampicin against 9/20 strains. The combinations of polymyxin B and aztreonam or meropenem showed synergy against 2/20 strains. Negligible resistance development against polymyxin B was detected. Synergy with polymyxin B and minocycline was associated with genes involved in efflux (presence of tet(B) , wildtype soxR and the marB mutation H44Q) and lipopolysaccharide synthesis ( eptA C27Y, lpxB mutations and lpxK L323S). Synergy with polymyxin B and rifampicin was associated with sequence variations in arnT , which plays a role in lipid A modification. Conclusion. Polymyxin B in combination with minocycline or rifampicin frequently showed positive interactions against NDM- and OXA-48-group-producing E. coli . Synergy was associated with genes encoding efflux and components of the bacterial outer membrane.

In Vitro Analytical System for Determining the Ability of Antibiotics at Residue Levels to Select for Resistance in Bacteria

1988 ◽  
Vol 71 (2) ◽  
pp. 295-298
Author(s):  
Marietta Suebrady ◽  
Robert J Strobel ◽  
Stanley E Katz
Keyword(s):  
Analytical Procedure ◽  
Inhibitory Concentration ◽  
Enteric Bacteria ◽  
E Coli ◽  
Resistant Population ◽  
Test Organisms ◽  
Residue Levels ◽  
Analytical System ◽  
Selection Of

Abstract An analytical procedure, based on the concept that exposure of bacteria to antibiotics will result in the selection of a resistant population, was developed. Two strains of enteric bacteria, Escherichia coli CS-1 and Enterobacter cloacae B520, which are sensitive to a wide variety of antibiotics, were used as the test organisms. E. coli CS-1 were exposed to 1.00 μg antibiotic or antimicrobial/mL; E. cloacae B520 were exposed to 0.01, 0.10, 0.50,1.00, and 5.00 μg/mL. Both organisms developed increased resistance to other antibiotics after exposure to chlortetracycline and oxytetracycline, as measured by the minimum inhibitory concentration (MIC). E. cloacae B520 showed increased resistance to ampicillin, oxytetracycline, and chloramphenicol after exposure to levels as low as 0.10 μg/mL. Exposure to streptomycin, sulfamethazine, tylosin, bacitracin, flavomycin, virginiamycin, and monensin at levels of 1.00 μg/mL did not increase the MIC. Exposure to 5.00 *tg streptomycin, sulfamethazine, tylosin, and monensin/mL increased the MIC ofE. cloacae to one of the antibiotic markers. These increased MICs exceeded the 95% confidence limits of the MIC values of the unexposed organisms.

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