od 530 hourly using a spectronic 20 until the turbidity of the broth reached a plateau in a complete growth curve the number of bacteria in the nutrient was determined by homogeneously plating 0 1 ml of serially diluted bacteria onto a nutrient agar plate and incubated at 37 u00b0 c for 18 24 hours the agar plates 9 cm in diameter with colony counts between 30 and 300 were selected for the measurement of bacteria a masterbatch of e coli broth was prepared by growing pure cultures in a nutrient broth difco detroit mich for 6 7 hours until a concentration of 7 u00d7 10 8 colony forming units cfu per ml was reached the turbidity at the wavelength of 650 nm was measured to be about 0 5 the masterbatch e coli broth was diluted with pbs phosphate buffered saline by a factor of 20 to obtain diluted e coli suspensions at a concentration of 3 5 u00d7 10 7 colony forming units per ml the mice used in this study were male balb c having a body weight around 25 g intraperitoneal injection of the diluted e coli suspensions were then administered to the mice prior to the injection of the.