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Abstract
Purpose:
The pathogenicity in Candida spp was attributed by several virulence factors such as production of tissue damaging extracellular enzymes, germ tube formation, hyphal morphogenesis and establishment of drug resistant biofilm. The objective of present study was to investigate the effects of silver nanoparticles (AgNPs) on growth, cell morphology and key virulence attributes of Candida species.
Methods:
AgNPs were synthesized by the using seed extract of Syzygium cumini (Sc), and were characterized by UV-Vis spectrophotometer, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM). ScAgNPs were used to evaluate their antifungal and antibacterial activity as well as their potent inhibitory effects on germ tube and biofilm formation and extracellular enzymes viz. phospholipases, proteinases, lipases and hemolysin secreted by Candida spp.
Results:
The MICs values of ScAgNPs were ranged from 0.125-0.250 mg/ml, whereas the MBCs and MFCs were 0.250 and 0.500 mg/ml, respectively. ScAgNPs significantly inhibit the production of phospholipases by 82.2, 75.7, 78.7, 62.5, and 65.8%; proteinases by 82.0, 72.0, 77.5, 67.0, and 83.7%; lipase by 69.4, 58.8, 60.0, 42.9, and 65.0%; and hemolysin by 62.8, 69.7, 67.2, 73.1, and 70.2% in C. albicans, C. tropicalis, C. dubliniensis, C. parapsilosis and C. krusei, respectively, at 500 μg/ml. ScAgNPs inhibit germ tube formation in C. albicans up to 97.1% at 0.25 mg/ml. LIVE/DEAD staining results showed that ScAgNPs almost completely inhibit biofilm formation in C. albicans. TEM analysis shows that ScAgNPs not only anchored onto the cell surface but also penetrated and accumulated in the cytoplasm that causes severe damage to the cell wall and cytoplasmic membrane.
Conclusion:
To summarize, the biosynthesized ScAgNPs strongly suppressed the multiplication, germ tube and biofilm formation and most importantly secretion of hydrolytic enzymes (viz. phospholipases, proteinases, lipases and hemolysin) by Candia spp. The present research work open several avenues of further study, such as to explore the molecular mechanism of inhibition of germ tubes and biofilm formation and suppression of production of various hydrolytic enzymes by Candida spp.
Acknowledgments
Mr. Mohammad Jalal is grateful to Maulana Azad National Fellowship, UGC, New Delhi, India for providing fellowship in the form of JRF. The authors are sincerely thankful to Ahmad Ali Khan and Sanjay Sharma Department of Microbiology, J.N. Medical College, Aligarh Muslim University, Aligarh, U.P India for their technical help and support. The authors thank the Aligarh Muslim University, Aligarh, India for providing instruments facilities and other items used in this study.
Disclosure
The authors declare that they have no conflicts of interest in this work.
Supplementary material
Figure S1 Ability of biofilm formation of C. albicans on BHI agar supplemented with Congo red and ScAgNPs. (A) Control (without ScAgNPs) showing black crystalline colonies indicate the exopolysaccharides production. Plates (B) and (C) treated with 0.025 and 0.05 mg/mL of ScAgNPs showing inhibition of exopolysaccharide synthesis.
Abbreviation: ScAgNPs, Syzygium cumini silver nanoparticles.
