Evaluation Strategies for Triple‐Drug Combinations against Carbapenemase‐Producing Klebsiella Pneumoniae in an In Vitro Hollow‐Fiber Infection Model

Abstract

Mounting antimicrobial resistance to carbapenemase-producing Klebsiella pneumoniae (CPKP) highlights the need to optimize currently available treatment options. The objective of this study was to explore alternative dosing strategies that limit the emergence of resistance to preserve the utility of last-line antibiotics by: (i) evaluating the pharmacodynamic (PD) killing activity of simulated humanized exposures to monotherapy and two-drug and three-drug combinations against CPKP bacterial isolates with different resistance mechanisms; and (ii) optimizing polymyxin B (PMB) exposure simulated in the three-drug combination regimens to maximize the killing activity. Two CPKP clinical isolates (BAA2146 (NDM-1) and BRKP76 (KPC-2)) were evaluated over 168 hours using a hollow-fiber infection model simulating clinically relevant PMB, fosfomycin, and meropenem dosing regimens. PMB-based three-drug combinations were further optimized by varying the initial exposure (0-24 hours) or maintenance dose received over the duration of treatment. The area under the bacterial load-versus-time curve (AUCFU) was used to determine PD activity. Overall reductions in PMB exposure ranged from 2 to 84%. BAA2146 and BRKP76 had median (range) AUCFUs of 11.0 (10.6-11.6) log 10 CFU hour/mL and 7.08 (7.04-11.9) log 10 CFU hour/mL, respectively. The PMB "front loaded" 2.5 mg/ kg/day + 0.5 mg/kg maintenance dose in combination with meropenem and fosfomycin was a promising regimen against BRKP76, with an overall reduction in PMB exposure of 56% while still eradicating the bacteria. Tailored triplecombination therapy allows for the optimization of dose and treatment duration of last-line agents like PMB to achieve adequate drug exposure and appropriate PD activity while minimizing the emergence of resistance.

Proof‐of‐concept for incorporating mechanistic insights from multi‐omics analyses of polymyxin B in combination with chloramphenicol against Klebsiella pneumoniae

“…minimize emergence of resistance using dynamic in vitro models of infection. [16][17][18][19] Chloramphenicol (CHL) is a broad-spectrum antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, was approved for clinical use in the late 1940s, and was the first antibiotic to be manufactured synthetically on a large scale. 20 These drugs were abandoned due to their toxicities: nephrotoxicity for polymyxins and aplastic anemia for CHL.…”

“…Given that polymyxin B (PMB), an old antibiotic, is still effective as a last line agent against infections caused by CRKP, there is a need to identify and develop novel PMB‐based combination therapies to conserve its utility 14,15 . Our group has previously explored and evaluated PMB‐based double and triple combination therapies that maintain efficacy and minimize emergence of resistance using dynamic in vitro models of infection 16–19 . Chloramphenicol (CHL) is a broad‐spectrum antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, was approved for clinical use in the late 1940s, and was the first antibiotic to be manufactured synthetically on a large scale 20 .…”

Losing the Battle but Winning the War: Can Defeated Antibacterials Form Alliances to Combat Drug-Resistant Pathogens?

“…Double combinations that utilize a polymyxin and fosfomycin have also been investigated in vitro against polymyxin-resistant KPCKP, and the combination was able to achieve synergy in time-killing experiments (albeit at high drug concentrations) and a hollow-fiber infection model [35,36]. In vitro dynamic model [33] In vivo rabbit osteomyelitis model [32] (meropenem) + colistin + gentamicin In vivo rabbit osteomyelitis model [32] (meropenem) + polymyxin B + fosfomycin In vitro dynamic model [37] (meropenem) + colistin + tigecycline In vitro dynamic model [33] (meropenem) + colistin and/or tigecycline and/or gentamicin Retrospective clinical [34] (meropenem) + (amikacin)…”

“…In vivo murine thigh model [42] Retrospective clinical [43,44] NDMKP (meropenem) + tigecycline In vitro dynamic model [45] (meropenem) + fosfomycin + polymyxin B In vitro dynamic model [37] (fosfomycin) + colistin In vitro dynamic model [46] (polymyxin B) + amikacin + aztreonam In vitro dynamic model [47] ˆDrugs were determined to be inactive if the pathogens' MIC was above the CLSI breakpoint for susceptibility, if available. Polymyxin MICs of 2 or higher were considered inactive.…”

Applications of the hollow-fibre infection model (HFIM) in viral infection studies

“…Most of the work done on the HFIM has focused on bacteria and antimicrobial testing. 11,[13][14][15] Although comprehensive literature on the use of the HFIM for performance evaluation of antimicrobial compounds exist, [16][17][18][19][20] the current literature about the applications of the HFIM to study viral infections is still lacking. This review therefore focuses on the applications of the HFIM in viral infection studies.…”