RESUMEN
Farnesol, a self-secreted quorum-sensing molecule (QSM) of Candida albicans, has been known to limit yeast-to-hyphal transition by blocking the RAS1-cAMP-PKA pathway. In a similar fashion, certain bacterial QSMs have also been reported to be successful in attenuating C. albicans biofilm and hyphal formation at relatively high cell density. This prompted us to investigate the antihyphal efficacy of certain bacterial QSMs through virtual docking against seminal drug targets, viz., CYCc and RAS1, that have been reported to be the hallmark players in C. albicans dimorphic virulence cascade. Against this backdrop, 64 QSMs belonging to five different bacterial QS signaling systems were subjected to initial virtual screening with farnesol as reference. Data of the virtual screening unveiled QSMs belonging to diketopiperazines (DKPs), i.e., 3-benzyl-6-isobutylidene-2,5-piperazinedione (QSSM 1157) and cyclo(l-Pro-l-Leu) (QSSM 1112), as potential inhibitors of CYCc and RAS1 with binding energies of -8.2 and -7.3 kcal mol-1, respectively. Further, the molecular dynamics simulations (for 50 ns) of CYCc-QSSM 1157 and RAS1-QSSM 1112 complexes revealed the mean ligand root mean square deviation (RMSD) values of 0.35 and 0.27 Å, respectively, which endorsed the rigid nature, less fluctuation in binding stiffness, and conformation of binding complexes. Furthermore, the identified two QSMs were found to be good in solubility, absorption, and permeation and less toxic in nature, as revealed by pharmacokinetics and toxicity analyses. In addition, the in vitro antihyphal assays using liquid and solid media, germ-tube experiment, and microscopic analysis strongly validated DKP-QSSM 1112 as a promising inhibitor of hyphal transition. Taken together, the present study unequivocally proves that DKPs can be used as potent inhibitors of C. albicans virulence dimorphism.
Asunto(s)
Candida albicans , Caracteres Sexuales , Farnesol/farmacología , Percepción de Quorum , VirulenciaRESUMEN
Aims@#The objective of the present study is to evaluate the possibility of reversing the resistance of pathogens to antibiotics using phytochemicals from plant extracts as antibiotic-adjuvant.@*Methodology and results@#Twenty-one plants were collected from Podhigai Hills, Tamil Nadu, India and tested in this study. The susceptibility of burn wound isolates (Pseudomonas aeruginosa and Staphylococcus aureus) to antibiotics and the adjuvant activity of the aqueous plant extracts were tested using well diffusion assay. The impact of the plant extracts on quorum sensing was assessed using Chromobacterium violaceum as the model organism. The antibiofilm activity of the adjuvant and antibiotics was determined by crystal violet assay. The isolates which were resistant to more than one class of antibiotics (aminoglycoside, cephalosporin, fluoroquinolone and penicillin) were designated as multidrug resistant bacteria. Combination of cefdinir-Citrullus colocynthis showed 17 mm inhibition zone which is greater than cefdinir (0 mm) against P. aeruginosa. The combination reduced quorum sensing with an inhibition zone of 30 mm. The same combination reduced 96% and 95% of the biofilm formed by P. aeruginosa and S. aureus, respectively at 16 h. Besides, cefdinir with Leucas aspera reduced quorum sensing with an inhibition zone of 28 mm. The combination reduced 94% and 95% of biofilm formed by P. aeruginosa and S. aureus, respectively at 16 h. The aqueous extract of C. colocynthis and L. aspera revealed the presence of flavonoids that possess adjuvant activity. @*Conclusion, significance and impact of study@#Cefdinir-C. colocynthis and cefdinir-L. aspera reversed the resistance of multi drug resistant bacteria to cefdinir. The flavonoids of C. colocynthis and L. aspera served as an adjuvant that potentiates the activity of cefdinir.
Asunto(s)
Farmacorresistencia Microbiana , FitoquímicosRESUMEN
Candida albicans and Staphylococcus epidermidis are important opportunistic human pathogens, which form mixed-species biofilms and cause recalcitrant device associated infections in clinical settings. Further to many reports suggesting the therapeutic potential of plant-derived monoterpenoids, this study investigated the interaction of the monoterpenoids carvacrol (C) and thymol (T) against mono- and mixed-species growth of C. albicans and S. epidermidis. C and T exhibited synergistic antimicrobial activity. The time-kill study and post-antimicrobial effect results revealed the effective microbicidal action of the C + T combination. Filamentation, surface coating assays and live-dead staining of biofilms determined the anti-hyphal, antiadhesion, and anti-biofilm activities of the C + T combination, respectively. Notably, this combination killed highly tolerant persister cells of mono-species and mixed-species biofilms and demonstrated less risk of resistance development. The collective data suggest that the C + T combination could act as an effective therapeutic agent against biofilm associated mono-species and mixed-species infections of C. albicans and S. epidermidis.