Aliquots (100 L) of the diluted bacteria suspension in phosphate buffered saline were then plated on LB agar and incubated at 37 C overnight. All the bactericidal tests were performed in triplicate for each sample and the results are expressed as mean  standard deviation (SD). The bacterial viability was determined by counting the colony numbers on LB agar plates from appropriate bacterial dilution and percent viability was obtained according to the following equation: