p.m. and (2) stationary. Biofilms were quantified using the standardized crystal violet method (O’Toole check details et al., 1999; Dusane et al., 2008a). Adhesion of bacteria to 96-well polycarbonate microtiter plate surfaces was carried out by inoculating 20 μL of overnight grown culture in 0.5 × LB containing 180 μL of the growth medium. The plates were incubated at 37 °C for 72 h and biofilm formation was estimated by a routine crystal

violet staining method (Dusane et al., 2008b). The experiments were carried out in triplicates. Biofilm formation was also analyzed in glass test tubes (Tomaras et al., 2003). The biofilms were formed by adding 0.1 mL of the culture to 10 mL LB (0.5 ×) dispensed Sirtuin inhibitor in glass test tubes. The experiment was performed in duplicates and

the cultures were incubated at 37 °C for 72 h under two sets of different conditions: (1) shaking at 200 r.p.m. and (2) stationary. After incubation, the medium was removed, the tubes were washed with distilled water, air dried and biofilms were assayed using the crystal violet method. Strains of Escherichia coli HB101 and Pseudomonas aeruginosa PA01 were used as controls for the biofilm experiments (Kazemi-Pour et al., 2007). In vitro assay of bacterial adhesion to the catheter surface was assessed as described earlier with some modifications (Sheth et al., 1983). The selected isolates used for this study were cultivated for 24 h at 30 °C in 0.5 × LB containing 0.25 × minimum

inhibitory concentration (MIC) (0.5 μg mL−1) and 0.5 × MIC (1 μg mL−1) concentrations new of colistin (Sigma, India). After the incubation period, antibiotic was removed from the culture by rinsing twice with sterile saline followed by centrifugation (6000 g for 10 min). The bacterial cells were resuspended in sterile saline and the OD of each suspension was measured colorimetrically at 540 nm to achieve the cell density equivalent to 1–5 × 107 CFU mL−1 (confirmed by plate count). Cultures without antibiotics were used as the controls. Urinary catheters (Rusch GmbH, Kemen, Germany), 7 mm in diameter were cut into 1.5-cm-long segments. The segments were then immersed in 13 × 100 mm tubes containing suspensions of the previously standardized strains and kept at room temperature for 30 min. After this contact, each fragment was placed in a tube (18 × 160 mm) containing 15 mL of sterile saline solution, and the tubes were manually inverted 40 times. This procedure was repeated 15 times, transferring the fragment to 15 tubes successively, with the objective of removing the nonadherent bacteria. After the 15 rinses, the catheter fragments were removed from the tube and rolled over the surface of 10 Petri dishes (90 × 15 mm) containing LB agar. After an incubation period of 24 h at 30 °C, the bacterial colonies were counted.