Five oysters were disserted every month and the
alimentary tract (0.5 g) was triturated in 1 mL normal saline (0.85%) and then
diluted with normal saline and smeared on nutrient agar medium and TCBS agar
plates for three proper gradients, three parallel groups for every gradient. All the
plates were layed up in biochemistry incubators at 28 1C for 96 h.