4341
Three different approaches were assayed : pre - incubation of bacteria and compounds before addition to cells ( competition ) ; pre - incubation of the cells with compounds ( exclusion ) ; and pre - incubation of cells with bacteria ( displacement ) .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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