An "Unlikely" Pair: The Antimicrobial Synergy of Polymyxin B in Combination with the Cystic Fibrosis Transmembrane Conductance Regulator Drugs KALYDECO and ORKAMBI.
Novel combination therapies are desperately needed for combating lung infections caused by bacterial "superbugs". This study aimed to investigate the synergistic antibacterial activity of polymyxin B in combination with the cystic fibrosis (CF) drugs KALYDECO (ivacaftor) and ORKAMBI (ivacaftor + lumacaftor) against Gram-negative pathogens that commonly colonize the CF lung, in particular, the problematic Pseudomonas aeruginosa. The in vitro synergistic activity of polymyxin B combined with ivacaftor or lumacaftor was assessed using checkerboard and static time-kill assays against a panel of polymyxin-susceptible and polymyxin-resistant P. aeruginosa isolates from the lungs of CF patients. Polymyxin B, ivacaftor, and lumacaftor were ineffective when used individually against polymyxin-resistant (MIC ≥ 4 mg/L) isolates. However, when used together, the combination of clinically relevant concentrations of polymyxin B (2 mg/L) combined with ivacaftor (8 mg/L) or ivacaftor (8 mg/L) + lumacaftor (8 mg/L) displayed synergistic killing activity against polymyxin-resistant P. aeruginosa isolates as demonstrated by a 100-fold decrease in the bacterial count (CFU/mL) even after 24 h. The combinations also displayed excellent antibacterial activity against P. aeruginosa under CF relevant conditions in a sputum medium assay. The combination of lumacaftor (alone) with polymyxin B showed additivity against P. aeruginosa. The potential antimicrobial mode of action of the combinations against P. aeruginosa was investigated using different methods. Treatment with the combinations induced cytosolic GFP release from P. aeruginosa cells and showed permeabilizing activity in the nitrocefin assay, indicating damage to both the outer and inner Gram-negative cell membranes. Moreover, scanning and transmission electron micrographs revealed that the combinations produce outer membrane damage to P. aeruginosa cells that is distinct from the effect of each compound per se. Ivacaftor was also shown to be a weak inhibitor of the bacterial DNA gyrase and topoisomerase IV with no effect on either human type I or type IIα topoisomerases. Lumacaftor displayed the ability to increase the cellular production of damaging reactive oxygen species. In summary, the combination of polymyxin B with KALYDECO or ORKAMBI exhibited synergistic activity against highly polymyxin-resistant P. aeruginosa CF isolates and can be potentially useful for otherwise untreatable CF lung infections.
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville, Victoria 3052, Australia.
Elena K
EK
Schneider
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville, Victoria 3052, Australia.
Mohammad A K
MA
Azad
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville, Victoria 3052, Australia.
Mei-Ling
ML
Han
Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University , 575 West Stadium Avenue, West Lafayette, Indiana 47907-2091, United States.
Qi
Q
Tony Zhou
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville, Victoria 3052, Australia.
Jiping
J
Wang
Institute for Molecular Bioscience, The University of Queensland , St Lucia, Queensland 4072, Australia.
Johnny X
JX
Huang
Institute for Molecular Bioscience, The University of Queensland , St Lucia, Queensland 4072, Australia.
Matthew A
MA
Cooper
Division of Infectious Diseases, Department of Medicine, University of Pittsburgh Medical Center , Liliane S. Kaufmann Building, 3471 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
Yohei
Y
Doi
Priority Research Centre in Reproductive Science, School of Environmental and Life Sciences, University of Newcastle , Callaghan, New South Wales 2308, Australia.
Mark A
MA
Baker
Center for Medicine Use and Safety, Monash University , 381 Royal Parade, Parkville, Victoria 3052, Australia.
Phillip J
PJ
Bergen
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida , 6900 Lake Nona Boulevard, Orlando, Florida 32816, United States.
Mark T
MT
Muller
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville, Victoria 3052, Australia.
Jian
J
Li
Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville, Victoria 3052, Australia.
Tony
T
Velkov
D000627:Aminophenols / Q000494:pharmacology*; D000631:Aminopyridines / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D052117:Benzodioxoles / Q000494:pharmacology*; D003550:Cystic Fibrosis / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D006801:Humans; D011112:Polymyxin B / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D015363:Quinolones / Q000494:pharmacology*
D000627:Aminophenols; D000631:Aminopyridines; D000900:Anti-Bacterial Agents; D052117:Benzodioxoles; D015363:Quinolones; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C545203:ivacaftor; C569105:lumacaftor; D011112:Polymyxin B
Pseudomonas aeruginosa; cystic fibrosis; ivacaftor; lumacaftor; polymyxin