Library screen

[Default Trumpet User]

Hi,
	I am working on the expression library of screening by polyclonal 
antibody. I am depressed by the false result. I use bacterial phage 
expressin system with ZAP II. When I did first screening, the signals were 
normal. There were two or three plaques which were positive in a 17 mm 
plate. Then,  Every plaques  of  second screening was positive in a 9 mm 
plate even through the plating solution was the mixtures of 4-5 plaque from 
the positive plaque and the neighboring plaques in the first screening 
plate. My blocking reagent was BSA, and I did preabsoption. 
	Did anybody have this problem before ? Do you have any suggestion? 
If my description is not clear, please tell me. I will describe more details 
and discuss with you.