AUTHOR=Yong Jiangyan , Zu Ruiling , Huang Xiaoxue , Ge Yiman , Li Yan 

TITLE=Synergistic Effect of Berberine Hydrochloride and Fluconazole Against Candida albicans Resistant Isolates

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01498

DOI=10.3389/fmicb.2020.01498

ISSN=1664-302X

ABSTRACT=<p>The emergence of resistant <italic>Candida albicans</italic> has made clinical fluconazole (FLC) treatment difficult. Improving sensitivity to FLC is an effective way to treat resistant isolates. Berberine hydrochloride (BBH) is a commonly used traditional Chinese medicine with antimicrobial effects, especially in resistant isolates. We investigated the molecular mechanisms underlying BBH and FLC synergism on biofilm-positive FLC-resistant <italic>C. albicans</italic> inhibition. Checkerboard microdilution assays and time-kill assays showed a strong synergistic effect between BBH and FLC in resistant <italic>C. albicans</italic> isolates, causing a significant 32–512-fold reduction in minimum inhibitory concentrations. BBH combined with FLC inhibited intracellular FLC efflux due to key efflux pump gene <italic>CDR1</italic> downregulation, whereas FLC alone induced high <italic>CDR1</italic> transcription in resistant strains. Further, BBH + FLC inhibited yeast adhesion, morphological hyphae transformation, and biofilm formation by downregulating the hyphal-specific genes <italic>ALS3</italic>, <italic>HWP1</italic>, and <italic>ECE1</italic>. BBH caused cytoplasmic Ca<sup>2+</sup> influx, while FLC alone did not induce high intracellular Ca<sup>2+</sup> levels. The vacuolar calcium channel gene <italic>YVC1</italic> was upregulated, while the vacuolar calcium pump gene <italic>PMC1</italic> was downregulated in the BBH + FLC and BBH alone groups. However, vacuolar calcium gene expression after FLC treatment was opposite in biofilm-positive FLC-resistant <italic>C. albicans</italic>, which might explain why BBH induces Ca<sup>2+</sup> influx. These results demonstrate that BBH + FLC exerts synergistic effects to increase FLC sensitivity by regulating multiple targets in FLC-resistant <italic>C. albicans</italic>. These findings further show that traditional Chinese medicines have multi-target antimicrobial effects that may inhibit drug-resistant strains. This study also found that the vacuolar calcium regulation genes <italic>YVC1</italic> and <italic>PMC1</italic> are key BBH + FLC targets which increase cytoplasmic Ca<sup>2+</sup> in resistant isolates, which might be critical for reversing biofilm-positive FLC-resistant <italic>C. albicans</italic>.</p>