B-236. Biofilm Formation by Candida spp. on in vitro Model of Albumin Coated Silica Beads (ACSB)

A. T. Abou Khalifa1, M. El-Azizi1, N. Khardori2;
1German Univ. in Cairo, New Cairo City, EGYPT, 2Southern Illinois Univ. Sch. of Med., Springfield, IL.

We tested the biofilm formation of 20 clinical isolates of Candida spp. namely, Candida albicans (16), Candida tropicalis (3), and Candida glabrata (1) by using an in vitro model consisting of bovine serum albumin (BSA)-coated silica beads (ACSB). Briefly, 100 mg of sterile silica beads were soaked overnight in 1 ml of BSA. The solution was aspirated and the beads were washed three times with PBS. One ml of Yeast Nitrogen Base (YNB) medium containing 1 X 109 cfu/ml portions of the tested isolates were added to the beads and the mixtures were shaked for 1 h at 50 rpm. The tubes containing the mixtures were incubated at 37oC without agitation. After 48 h, the contents of the tubes were aspirated and the beads were washed three times with PBS. The beads were then suspended in 1 ml portions of sterile normal saline and sonicated to dislodge the biofilms. Viable cells were finally determined by viable count on Sabouraud’s agar.The ACSB successfully demonstrated the capability of adherence and biofilm formation of the tested isolates. All tested isolates were capable of forming biofilm on the beads. The mean log cfu/ml of adherent C. albicans and C tropicalis were 7.36 (±0.98), and 7.16 (±0.81) respectively. The tested isolate of C. glabrata was also highly adherent with log cfu/ml 7.38. The beads were also used to visualize the biofilms microscopically. ACSB is a good model to demonstrate the adherence and biofilm formation of different Candida spp