Rapid Detection of <i>Escherichia coli</i> in Fresh Foods Using a Combination of Enrichment and PCR Analysis.

Abstract

The objective of this study was to determine the minimum enrichment time for different types of food matrix (pork, beef, and fresh-cut lettuce) in an effort to improve <i>Escherichia coli</i> detection efficiency. Fresh pork (20 g), beef (20 g), and fresh-cut lettuce (20 g) were inoculated at 1, 2, and 3 Log CFU/g of <i>Escherichia coli</i>. Samples were enriched in filter bags for 3 or 5 h at 44.5°C, depending on sample type. <i>E. coli</i> cell counts in the samples were enriched in <i>E. coli</i> (EC) broth at 3 or 5 h. One milliliter of the enriched culture medium was used for DNA extraction, and PCR assays were performed using primers specific for <i>uidA</i> gene. To detect <i>E. coli</i> (<i>uidA</i>) in the samples, a 3-4 Log CFU/mL cell concentration was required. However, <i>E. coli</i> was detected at 1 Log CFU/g in fresh pork, beef, and fresh-cut lettuce after 5, 5, and 3-h enrichment, respectively. In conclusion, 5-h enrichment for fresh meats and 3-h enrichment for fresh-cut lettuce in EC broth at 44.5°C, and PCR analysis using <i>uidA</i> gene-specific primers were appropriate to detect <i>E. coli</i> rapidly in food samples.