Antifungaldrugresistanceisasignificantclinicalproblem,andantifungalagentsthatcanevaderesistanceareurgentlyneeded.Ininfectiveniches,resistantorganismsoftenco-existedwithsensitiveones,orasubpopulationofantibiotic-susceptibleorganismsmayevolveintoresistantonesduringantibiotictreatmentandeventuallydominatethewholepopulation.Inthisstudy,weestablishedaco-cultureassayinwhichanazole-resistantCandidaalbicansstrainwasmixedwithasusceptiblestrainlabeledwithgreenfluorescentproteintomimicinvivoconditionsandscreenforantifungaldrugs.Fluconazolewasusedasapositivecontroltoverifythevalidityofthisco-cultureassay.FivenaturalmoleculesexhibitedantifungalactivityagainstbothsusceptibleandresistantC.albicans.Twoofthesecompounds,retigericacidB(RAB)andriccardinD(RD),preferentiallyinhibitedC.albicansstrainsinwhichtheeffluxpumpMDR1wasactivated.Thisselectivitywasattributedtogreaterintracellularaccumulationofthedrugsintheresistantstrains.Changesinsterolandlipidcompositionswereobservedintheresistantstrainscomparedtothesusceptiblestrain,andmightincreasecellpermeabilitytoRABandRD.Inaddition,RABandRDinterferedwiththesterolpathway,furtheraggregatingthedecreaseinergosterolinthesterolsynthesispathwayintheMDR1-activatedstrains.Ourfindingshereprovideanalternativeforcombatingresistantpathogenicfungi.
