Evaluation of Pharmacokinetic/Pharmacodynamic Model-Based Optimized Combination Regimens against Multidrug-Resistant Pseudomonas aeruginosa in a Murine Thigh Infection Model by Using Humanized Dosing Schemes

ABSTRACT We previously optimized imipenem and tobramycin combination regimens against a double-resistant clinical Pseudomonas aeruginosa isolate by using in vitro infection models, mechanism-based pharmacokinetic/pharmacodynamic modeling (MBM), and Monte Carlo simulations. The current study aimed to evaluate these regimens in a neutropenic murine thigh infection model and to characterize the time course of bacterial killing and regrowth via MBM. We studied monotherapies and combinations of imipenem with tobramycin in vivo against the double-resistant clinical P. aeruginosa isolate by using humanized dosing schemes. Viable count profiles of total and resistant populations were quantified over 24 h. Tobramycin monotherapy (7 mg/kg every 24 h [q24h] as a 0.5-h infusion) was ineffective. Imipenem monotherapies (continuous infusion of 4 or 5 g/day with a 1-g loading dose) yielded 2.47 or 2.57 log10 CFU/thigh killing at 6 h. At 24 h, imipenem at 4 g/day led to regrowth up to the initial inoculum (4.79 ± 0.26 log10 CFU/thigh), whereas imipenem at 5 g/day displayed 1.75 log10 killing versus the initial inoculum. The combinations (i.e., imipenem at 4 or 5 g/day plus tobramycin) provided a clear benefit, with bacterial killing of ≥2.51 or ≥1.50 log10 CFU/thigh compared to the respective most active monotherapy at 24 h. No colonies were detected on 3×MIC agar plates for combinations, whereas increased resistance (at 3×MIC) emerged for monotherapies (except imipenem at 5 g/day). MBM suggested that tobramycin considerably enhanced the imipenem target site concentration up to 2.6-fold. The combination regimens, rationally optimized via a translational modeling approach, demonstrated substantially enhanced bacterial killing and suppression of regrowth in vivo against a double-resistant isolate and are therefore promising for future clinical evaluation.

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Optimization of Synergistic Combination Regimens against Carbapenem- and Aminoglycoside-Resistant Clinical Pseudomonas aeruginosa Isolates via Mechanism-Based Pharmacokinetic/Pharmacodynamic Modeling

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01011-16 ◽

2016 ◽

Vol 61 (1) ◽

Cited By ~ 15

Author(s):

Rajbharan Yadav ◽

Jürgen B. Bulitta ◽

Roger L. Nation ◽

Cornelia B. Landersdorfer

Keyword(s):

Pseudomonas Aeruginosa ◽

Multidrug Resistant ◽

Viable Count ◽

Resistant Isolate ◽

Pharmacodynamic Modeling ◽

Combination Regimen ◽

Bacterial Killing ◽

Content Type ◽

Dosage Regimens ◽

Combination Regimens

ABSTRACT Optimizing antibiotic combinations is promising to combat multidrug-resistant Pseudomonas aeruginosa. This study aimed to systematically evaluate synergistic bacterial killing and prevention of resistance by carbapenem and aminoglycoside combinations and to rationally optimize combination dosage regimens via a mechanism-based mathematical model (MBM). We studied monotherapies and combinations of imipenem with tobramycin or amikacin against three difficult-to-treat double-resistant clinical P. aeruginosa isolates. Viable-count profiles of total and resistant populations were quantified in 48-h static-concentration time-kill studies (inoculum, 107.5 CFU/ml). We rationally optimized combination dosage regimens via MBM and Monte Carlo simulations against isolate FADDI-PA088 (MIC of imipenem [MICimipenem] of 16 mg/liter and MICtobramycin of 32 mg/liter, i.e., both 98th percentiles according to the EUCAST database). Against this isolate, imipenem (1.5× MIC) combined with 1 to 2 mg/liter tobramycin (MIC, 32 mg/liter) or amikacin (MIC, 4 mg/liter) yielded ≥2-log10 more killing than the most active monotherapy at 48 h and prevented resistance. For all three strains, synergistic killing without resistance was achieved by ≥0.88× MICimipenem in combination with a median of 0.75× MICtobramycin (range, 0.032× to 2.0× MICtobramycin) or 0.50× MICamikacin (range, 0.25× to 0.50× MICamikacin). The MBM indicated that aminoglycosides significantly enhanced the imipenem target site concentration up to 3-fold; achieving 50% of this synergistic effect required aminoglycoside concentrations of 1.34 mg/liter (if the aminoglycoside MIC was 4 mg/liter) and 4.88 mg/liter (for MICs of 8 to 32 mg/liter). An optimized combination regimen (continuous infusion of imipenem at 5 g/day plus a 0.5-h infusion with 7 mg/kg of body weight tobramycin) was predicted to achieve >2.0-log10 killing and prevent regrowth at 48 h in 90.3% of patients (median bacterial killing, >4.0 log10 CFU/ml) against double-resistant isolate FADDI-PA088 and therefore was highly promising.

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Meropenem Combined with Ciprofloxacin Combats Hypermutable Pseudomonas aeruginosa from Respiratory Infections of Cystic Fibrosis Patients

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01150-18 ◽

2018 ◽

Vol 62 (11) ◽

Cited By ~ 9

Author(s):

Vanessa E. Rees ◽

Rajbharan Yadav ◽

Kate E. Rogers ◽

Jürgen B. Bulitta ◽

Veronika Wirth ◽

...

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Time Course ◽

Respiratory Infections ◽

Resistant Bacteria ◽

Infection Model ◽

Time Curve ◽

Bacterial Killing ◽

Content Type ◽

Concentration Time

ABSTRACT Hypermutable Pseudomonas aeruginosa organisms are prevalent in chronic respiratory infections and have been associated with reduced lung function in cystic fibrosis (CF); these isolates can become resistant to all antibiotics in monotherapy. This study aimed to evaluate the time course of bacterial killing and resistance of meropenem and ciprofloxacin in combination against hypermutable and nonhypermutable P. aeruginosa. Static concentration time-kill experiments over 72 h assessed meropenem and ciprofloxacin in mono- and combination therapies against PAO1 (nonhypermutable), PAOΔmutS (hypermutable), and hypermutable isolates CW8, CW35, and CW44 obtained from CF patients with chronic respiratory infections. Meropenem (1 or 2 g every 8 h [q8h] as 3-h infusions and 3 g/day as a continuous infusion) and ciprofloxacin (400 mg q8h as 1-h infusions) in monotherapies and combinations were further evaluated in an 8-day hollow-fiber infection model study (HFIM) against CW44. Concentration-time profiles in lung epithelial lining fluid reflecting the pharmacokinetics in CF patients were simulated and counts of total and resistant bacteria determined. All data were analyzed by mechanism-based modeling (MBM). In the HFIM, all monotherapies resulted in rapid regrowth with resistance at 48 h. The maximum daily doses of 6 g meropenem (T>MIC of 80% to 88%) and 1.2 g ciprofloxacin (area under the concentration-time curve over 24 h in the steady state divided by the MIC [AUC/MIC], 176), both given intermittently, in monotherapy failed to suppress regrowth and resulted in substantial emergence of resistance (≥7.6 log10 CFU/ml resistant populations). The combination of these regimens achieved synergistic killing and suppressed resistance. MBM with subpopulation and mechanistic synergy yielded unbiased and precise curve fits. Thus, the combination of 6 g/day meropenem plus ciprofloxacin holds promise for future clinical evaluation against infections by susceptible hypermutable P. aeruginosa.

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Meropenem-Tobramycin Combination Regimens Combat Carbapenem-Resistant Pseudomonas aeruginosa in the Hollow-Fiber Infection Model Simulating Augmented Renal Clearance in Critically Ill Patients

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01679-19 ◽

2019 ◽

Vol 64 (1) ◽

Author(s):

Rajbharan Yadav ◽

Phillip J. Bergen ◽

Kate E. Rogers ◽

Carl M. J. Kirkpatrick ◽

Steven C. Wallis ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Hollow Fiber ◽

Critically Ill Patients ◽

Infection Model ◽

Augmented Renal Clearance ◽

Bacterial Killing ◽

Content Type ◽

Carbapenem Resistant ◽

Combination Regimens ◽

Rapid Regrowth

ABSTRACT Augmented renal clearance (ARC) is common in critically ill patients and is associated with subtherapeutic concentrations of renally eliminated antibiotics. We investigated the impact of ARC on bacterial killing and resistance amplification for meropenem and tobramycin regimens in monotherapy and combination. Two carbapenem-resistant Pseudomonas aeruginosa isolates were studied in static-concentration time-kill studies. One isolate was examined comprehensively in a 7-day hollow-fiber infection model (HFIM). Pharmacokinetic profiles representing substantial ARC (creatinine clearance of 250 ml/min) were generated in the HFIM for meropenem (1 g or 2 g administered every 8 h as 30-min infusion and 3 g/day or 6 g/day as continuous infusion [CI]) and tobramycin (7 mg/kg of body weight every 24 h as 30-min infusion) regimens. The time courses of total and less-susceptible bacterial populations and MICs were determined for the monotherapies and all four combination regimens. Mechanism-based mathematical modeling (MBM) was performed. In the HFIM, maximum bacterial killing with any meropenem monotherapy was ∼3 log10 CFU/ml at 7 h, followed by rapid regrowth with increases in resistant populations by 24 h (meropenem MIC of up to 128 mg/liter). Tobramycin monotherapy produced extensive initial killing (∼7 log10 at 4 h) with rapid regrowth by 24 h, including substantial increases in resistant populations (tobramycin MIC of 32 mg/liter). Combination regimens containing meropenem administered intermittently or as a 3-g/day CI suppressed regrowth for ∼1 to 3 days, with rapid regrowth of resistant bacteria. Only a 6-g/day CI of meropenem combined with tobramycin suppressed regrowth and resistance over 7 days. MBM described bacterial killing and regrowth for all regimens well. The mode of meropenem administration was critical for the combination to be maximally effective against carbapenem-resistant P. aeruginosa.

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Optimization of Polymyxin B in Combination with Doripenem To Combat Mutator Pseudomonas aeruginosa

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02377-15 ◽

2016 ◽

Vol 60 (5) ◽

pp. 2870-2880 ◽

Cited By ~ 9

Author(s):

Neang S. Ly ◽

Zackery P. Bulman ◽

Jürgen B. Bulitta ◽

Christopher Baron ◽

Gauri G. Rao ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Time Course ◽

Excision Repair ◽

Polymyxin B ◽

Pharmacodynamic Modeling ◽

Wild Type ◽

Bacterial Killing ◽

Content Type ◽

Mutator Strains ◽

Base Excision

ABSTRACTDevelopment of spontaneous mutations inPseudomonas aeruginosahas been associated with antibiotic failure, leading to high rates of morbidity and mortality. Our objective was to evaluate the pharmacodynamics of polymyxin B combinations against rapidly evolvingP. aeruginosamutator strains and to characterize the time course of bacterial killing and resistance via mechanism-based mathematical models. Polymyxin B or doripenem alone and in combination were evaluated against sixP. aeruginosastrains: wild-type PAO1, mismatch repair (MMR)-deficient (mutSandmutL) strains, and 7,8-dihydro-8-oxo-deoxyguanosine system (GO) base excision repair (BER)-deficient (mutM,mutT, andmutY) strains over 48 h. Pharmacodynamic modeling was performed using S-ADAPT and facilitated by SADAPT-TRAN. Mutator strains displayed higher mutation frequencies than the wild type (>600-fold). Exposure to monotherapy was followed by regrowth, even at high polymyxin B concentrations of up to 16 mg/liter. Polymyxin B and doripenem combinations displayed enhanced killing activity against all strains where complete eradication was achieved for polymyxin B concentrations of >4 mg/liter and doripenem concentrations of 8 mg/liter. Modeling suggested that the proportion of preexisting polymyxin B-resistant subpopulations influenced the pharmacodynamic profiles for each strain uniquely (fraction of resistance values are −8.81 log10for the wild type, −4.71 for themutSmutant, and −7.40 log10for themutMmutant). Our findings provide insight into the optimization of polymyxin B and doripenem combinations againstP. aeruginosamutator strains.

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Pharmacodynamic Evaluation of Plasma and Epithelial Lining Fluid Exposures of Amikacin against Pseudomonas aeruginosa in a Dynamic In Vitro Hollow-Fiber Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00879-20 ◽

2020 ◽

Vol 64 (9) ◽

Author(s):

Aaron J. Heffernan ◽

Fekade B. Sime ◽

Derek S. Sarovich ◽

Michael Neely ◽

Yarmarly Guerra-Valero ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Hollow Fiber ◽

Infection Model ◽

High Dose ◽

Epithelial Lining ◽

Bacterial Killing ◽

Epithelial Lining Fluid ◽

Content Type ◽

Initial Inoculum

ABSTRACT Given that aminoglycosides, such as amikacin, may be used for multidrug-resistant Pseudomonas aeruginosa infections, optimization of therapy is paramount for improved treatment outcomes. This study aims to investigate the pharmacodynamics of different simulated intravenous amikacin doses on susceptible P. aeruginosa to inform ventilator-associated pneumonia (VAP) and sepsis treatment choices. A hollow-fiber infection model with two P. aeruginosa isolates (MICs of 2 and 8 mg/liter) with an initial inoculum of ∼108 CFU/ml was used to test different amikacin dosing regimens. Three regimens (15, 25, and 50 mg/kg) were tested to simulate a blood exposure, while a 30 mg/kg regimen simulated the epithelial lining fluid (ELF) for potential respiratory tract infection. Data were described using a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model. Whole-genome sequencing was used to identify mutations associated with resistance emergence. While bacterial density was reduced by >6 logs within the first 12 h in simulated blood exposures following this initial bacterial kill, there was amplification of a resistant subpopulation with ribosomal mutations that were likely mediating amikacin resistance. No appreciable bacterial killing occurred with subsequent doses. There was less (<5 log) bacterial killing in the simulated ELF exposure for either isolate tested. Simulation studies suggested that a dose of 30 and 50 mg/kg may provide maximal bacterial killing for bloodstream and VAP infections, respectively. Our results suggest that amikacin efficacy may be improved with the use of high-dose therapy to rapidly eliminate susceptible bacteria. Subsequent doses may have reduced efficacy given the rapid amplification of less-susceptible bacterial subpopulations with amikacin monotherapy.

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Activity of Meropenem-Vaborbactam againstPseudomonas aeruginosaandAcinetobacter baumanniiin a Neutropenic Mouse Thigh Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01665-18 ◽

2018 ◽

Vol 63 (1) ◽

Cited By ~ 5

Author(s):

Mojgan Sabet ◽

Ziad Tarazi ◽

David C. Griffith

Keyword(s):

Pseudomonas Aeruginosa ◽

Acinetobacter Baumannii ◽

Clinical Isolates ◽

Infection Model ◽

Model Data ◽

Bacterial Killing ◽

Content Type

ABSTRACTWe have evaluated the activity of meropenem-vaborbactam against clinical isolates ofPseudomonas aeruginosaandAcinetobacter baumanniiin a neutropenic mouse thigh infection model. Data show that meropenem-vaborbactam regimens equivalent to 3-h infusions every 8 h with 2 g meropenem and 2 g vaborbactam produced bacterial killing against strains with MICs of 2 to 16 mg/liter and suggests that this combination may have utility in the treatment of infections caused byP. aeruginosaandA. baumannii.

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Efficacy of Humanized Cefiderocol Exposures over 72 Hours against a Diverse Group of Gram-Negative Isolates in the Neutropenic Murine Thigh Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01040-18 ◽

2018 ◽

Vol 63 (2) ◽

pp. e01040-18 ◽

Cited By ~ 3

Author(s):

Sean M. Stainton ◽

Marguerite L. Monogue ◽

Masakatsu Tsuji ◽

Yoshinori Yamano ◽

Roger Echols ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Acinetobacter Baumannii ◽

Infection Model ◽

Diverse Group ◽

Gram Negative ◽

Content Type ◽

Adaptive Resistance

ABSTRACT Herein, we evaluated sustainability of humanized exposures of cefiderocol in vivo over 72 h against pathogens with cefiderocol MICs of 0.5 to 16 μg/ml in the neutropenic murine thigh model. In Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacteriaceae displaying MICs of 0.5 to 8 μg/ml (n = 11), sustained kill was observed at 72 h among 9 isolates. Postexposure MICs revealed a single 2-dilution increase in one animal compared with controls (1/54 samples, 1.8%) at 72 h. Adaptive resistance during therapy was not observed.

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Investigation of Novel pmrB and eptA Mutations in Isogenic Acinetobacter baumannii Isolates Associated with Colistin Resistance and Increased Virulence In Vivo

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01586-18 ◽

2019 ◽

Vol 63 (3) ◽

Cited By ~ 18

Author(s):

Stefanie Gerson ◽

Jonathan W. Betts ◽

Kai Lucaßen ◽

Carolina Silva Nodari ◽

Julia Wille ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Lipid A ◽

Galleria Mellonella ◽

Resistance Mechanism ◽

Resistant Isolate ◽

Infection Model ◽

Colistin Resistance ◽

Strain Specificity ◽

Content Type

ABSTRACT Colistin resistance in Acinetobacter baumannii is of great concern and is a threat to human health. In this study, we investigate the mechanisms of colistin resistance in four isogenic pairs of A. baumannii isolates displaying an increase in colistin MICs. A mutation in pmrB was detected in each colistin-resistant isolate, three of which were novel (A28V, I232T, and ΔL9-G12). Increased expression of pmrC was shown by semi-quantitative reverse transcription-PCR (qRT-PCR) for three colistin-resistant isolates, and the addition of phosphoethanolamine (PEtN) to lipid A by PmrC was revealed by mass spectrometry. Interestingly, PEtN addition was also observed in some colistin-susceptible isolates, indicating that this resistance mechanism might be strain specific and that other factors could contribute to colistin resistance. Furthermore, the introduction of pmrAB carrying the short amino acid deletion ΔL9-G12 into a pmrAB knockout strain resulted in increased pmrC expression and lipid A modification, but colistin MICs remained unchanged, further supporting the strain specificity of this colistin resistance mechanism. Of note, a mutation in the pmrC homologue eptA and a point mutation in ISAba1 upstream of eptA were associated with colistin resistance and increased eptA expression, which is a hitherto undescribed resistance mechanism. Moreover, no cost of fitness was observed for colistin-resistant isolates, while the virulence of these isolates was increased in a Galleria mellonella infection model. Although the mutations in pmrB were associated with colistin resistance, PEtN addition appears not to be the sole factor leading to colistin resistance, indicating that the mechanism of colistin resistance is far more complex than previously suspected and is potentially strain specific.

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Mechanism-Based Pharmacokinetic/Pharmacodynamic Modeling of Aerosolized Colistin in a Mouse Lung Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01965-17 ◽

2017 ◽

Vol 62 (3) ◽

Cited By ~ 4

Author(s):

Yu-Wei Lin ◽

Qi Tony Zhou ◽

Mei-Ling Han ◽

Nikolas J. Onufrak ◽

Ke Chen ◽

...

Keyword(s):

Critically Ill ◽

Critically Ill Patients ◽

Pharmacodynamic Modeling ◽

Mouse Lung ◽

Infection Model ◽

Bacterial Reduction ◽

Bacterial Killing ◽

Deterministic Simulation ◽

Dosage Regimens

ABSTRACTOptimized dosage regimens of aerosolized colistin (as colistin methanesulfonate [CMS]) are urgently required to maximize bacterial killing against multidrug-resistant Gram-negative bacteria while minimizing toxicity. This study aimed to develop a mechanism-based pharmacokinetic (PK)/pharmacodynamic (PD) model (MBM) for aerosolized colistin based upon PK/PD data in neutropenic infected mice and to perform a deterministic simulation with the PK of aerosolized colistin (as CMS) in critically ill patients.In vivotime-kill experiments were carried out with three different strains ofPseudomonas aeruginosa. An MBM was developed in S-ADAPT and evaluated by assessing its ability to predict the PK/PD index associated with efficacy in mice. A deterministic simulation with human PK data was undertaken to predict the efficacy of current dosage regimens of aerosolized colistin in critically ill patients. In the final MBM, the total bacterial population for each isolate consisted of colistin-susceptible and -resistant subpopulations. The antimicrobial efficacy of aerosolized colistin was best described by a sigmoidalEmaxmodel whereby colistin enhanced the rate of bacterial death. Deterministic simulation with human PK data predicted that an inhalational dosage regimen of 60 mg colistin base activity (CBA) every 12 h is needed to achieve a ≥2-log10bacterial reduction (as the number of CFU per lung) in critically ill patients at 24 h after commencement of inhaled therapy. In conclusion, the developed MBM is a useful tool for optimizing inhalational dosage regimens of colistin. Clinical studies are warranted to validate and refine our MBM for aerosolized colistin.

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Aminoglycoside Concentrations Required for Synergy with Carbapenems against Pseudomonas aeruginosa Determined via Mechanistic Studies and Modeling

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00722-17 ◽

2017 ◽

Vol 61 (12) ◽

Cited By ~ 10

Author(s):

Rajbharan Yadav ◽

Jürgen B. Bulitta ◽

Elena K. Schneider ◽

Beom Soo Shin ◽

Tony Velkov ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Outer Membrane ◽

Time Course ◽

Membrane Damage ◽

Confocal Imaging ◽

Mechanistic Studies ◽

Bacterial Killing ◽

Content Type ◽

Uptake Data ◽

Time Kill

ABSTRACT This study aimed to systematically identify the aminoglycoside concentrations required for synergy with a carbapenem and characterize the permeabilizing effect of aminoglycosides on the outer membrane of Pseudomonas aeruginosa. Monotherapies and combinations of four aminoglycosides and three carbapenems were studied for activity against P. aeruginosa strain AH298-GFP in 48-h static-concentration time-kill studies (SCTK) (inoculum: 107.6 CFU/ml). The outer membrane-permeabilizing effect of tobramycin alone and in combination with imipenem was characterized via electron microscopy, confocal imaging, and the nitrocefin assay. A mechanism-based model (MBM) was developed to simultaneously describe the time course of bacterial killing and prevention of regrowth by imipenem combined with each of the four aminoglycosides. Notably, 0.25 mg/liter of tobramycin, which was inactive in monotherapy, achieved synergy (i.e., ≥2-log10 more killing than the most active monotherapy at 24 h) combined with imipenem. Electron micrographs, confocal image analyses, and the nitrocefin uptake data showed distinct outer membrane damage by tobramycin, which was more extensive for the combination with imipenem. The MBM indicated that aminoglycosides enhanced the imipenem target site concentration up to 4.27-fold. Tobramycin was the most potent aminoglycoside to permeabilize the outer membrane; tobramycin (0.216 mg/liter), gentamicin (0.739 mg/liter), amikacin (1.70 mg/liter), or streptomycin (5.19 mg/liter) was required for half-maximal permeabilization. In summary, our SCTK, mechanistic studies and MBM indicated that tobramycin was highly synergistic and displayed the maximum outer membrane disruption potential among the tested aminoglycosides. These findings support the optimization of highly promising antibiotic combination dosage regimens for critically ill patients.

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