ABSTRACT
Several tests used in the microbiological examination of foods are qualitative in nature (presence/absence), including tests for the detection of Salmonella, Listeria monocytogenes, Yersinia enterocolitica, Campylobacter, Escherichia coli O157:H7, Vibrio cholerae and Vibrio parahaemolyticus. Enrichment is a critical step of presence/absence tests for several reasons. The first reason is that the population of pathogens in the samples is normally low, making it necessary to increase the number of cells to detectable quantities. The second reason is that in most industrially processed foods, the cells of the target microorganism are injured by processing, thus requiring the recovery of the injured cells. The objective of pre-enrichment is to repair injured cells, offering conditions for their recovery, but at the same time, without favoring too much the growth of competing microflora. The objective of selective enrichment is to inhibit the competing microflora present in the samples, favoring at the same time multiplication of the target microorganism.
