**2. Material and methods**

The present study was conducted from 2009 to 2012. A total number of 350 bacterial and 50 Candida strains were studied. The microbial strains were isolated from different clinical specimens like urine, blood, pus and wound swab, endotracheal aspirate, urinary catheter tip, central venous catheter tip etc. All the microbial strains were identified by conventional methods [55]. We used microtitre plate biofilm assay to detect microbial attachment to an abiotic surface [56].

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**12.** Then the optical density of each well containing 125μl solution was measured at a wavelength of 545nm in an ELISA reader. As each strain was put in triplicate the average of the three readings were taken.

The biofilm formation of different strains were classified in three groups according to the cut off OD. The cut off OD (ODc) for the microtiter plate test was defined as three standard deviations above the mean OD of the negative control. Isolates were classified into four groups as nonadheremt, weakly adherent, moderately adherent and strongly adherent according to Stepanovi et al [57].
