Abstract
Purpose :
To ascertain whether antibiotic resistance and biofilm forming potential in Candida albicans isolated from patients with keratitis and cellulitis are positively correlated at the level of gene expression
Methods :
Susceptibility of the seven C. albicans isolates, from six keratitis and one orbital cellulitis patients to six antibiotics was determined by E test. Biofilm was assessed and confirmed by scanning electron microscopy (SEM) and confocal microscopy (CM). Gene expression of 30 different genes coding for biofilm formation (adhesion and transcription factors) and virulence (aspartyl proteinase and phospholipases) was first compared between C. albicans L-391/2015 which has the potential to form biofilm and C. albicans L-726/2011 cells which lacked the ability to form biofilm by Real-time PCR. Subsequently 20 genes that were up regulated in expression in the biofilm forming C. albicans were monitored to evaluate the temporal expression of the genes. Genes which showed > two fold expression compared to the 4 hr time point with p value <0.05 were considered as significantly expressed.
Results :
Four out of seven C. albicans were susceptible to Amphotericin B, Itraconazole, Voriconazole, Caspofungin, Fluconazole and Natamycin and three were resistant to one or more of the antibiotics. One resistant (itraconazole, voriconazole, fluconazole) isolate L-391/15 (from keratitis) was positive for biofilm formation. SEM indicated progressive deposition of biofilm from a single adherent layer of cells at 24 h to multiple layers by 72 h. CM confirmed that the thickness of biofilm increased from 5.2 μm at 24 h to 15 μm at 72 h. Further Real-time PCR indicated that 20 genes involved in virulence and biofilm were up-regulated in the biofilm positive isolate. We also observed time-dependent increase in expression of virulence genes such as drug transporters (mnt4, mdr1), proteinases (sap1, sap3, sap5, sap7, sap10), phospholipase genes (plb1, plb2, plc, pld), ATPases (pmr) and genes involved in biofilm such as the transcriptional factors (tup1, zap, efg) and adhesion genes (och, asl, hwp).
Conclusions :
This is the first study on gene expression analysis of an ocular C. albicans with a potential to form biofilm. The genes up regulated during biofilm could serve as potential targets for developing therapeutic strategies.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.