Quantitative determination of biofilm was made using microtiter plate adhesion assay in accordance with Stepanovic et al. (2000); Perez et al. (2011); Mulla and Revdiwala (2011) with some modifications. Briefly, three to five colonies were suspended with 5 ml of Trypticasesoy broth (TSB) (HiMedia, India) and incubated for 24 hrs. Then, diluted and adjusted to 0.5 McFarland turbidity standards to reach 105 CFU/ml. An aliquot of 200 μL of diluted bacterial suspension with 0.25% glucose (BDH, England), was added to each well of 96-well flat-bottomed polystyrene microtitre plates (Div.Becton, Dickinson &Co. Oxnard ,California, USA) and incubated for 18-24 hrs. at 37°C. Media with suspended bacteria were then removed; the plates washed carefully 3-4 times with sterile distilled water and air-dried, then stained with 200 μL of 0.9% crystal violet (Fluka, Switzerland). After washing the dye, the attached bacteria solubilized with 95% ethanol and the optical density of the adherent biofilm was determined twice with a filter of 450/630nm in ELISA reader (STAT-FAX 3200, USA). In our experiment 200 μL of TSB broth with 0.25% glucose were used as a negative control to obtain a background absorbance, which was then deducted from absorbance values obtained from the wells containing study isolates. All isolates were tested in triplicate