Rapid Detection of Escherichia coli in Fresh Foods Using a Combination of Enrichment and PCR Analysis

  • Choi, Yukyung ;
  • Lee, Sujung ;
  • Lee, Heeyoung ;
  • Lee, Soomin ;
  • Kim, Sejeong ;
  • Lee, Jeeyeon ;
  • Ha, Jimyeong ;
  • Oh, Hyemin ;
  • Lee, Yewon ;
  • Kim, Yujin ;
  • Yoon, Yohan
  • Received : 2018.05.01
  • Accepted : 2018.07.22
  • Published : 2018.08.31


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 Escherichia coli 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 Escherichia coli. Samples were enriched in filter bags for 3 or 5 h at $44.5^{\circ}C$, depending on sample type. E. coli cell counts in the samples were enriched in E. coli (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 uidA gene. To detect E. coli (uidA) in the samples, a 3-4 Log CFU/mL cell concentration was required. However, E. coli 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 $44.5^{\circ}C$, and PCR analysis using uidA gene-specific primers were appropriate to detect E. coli rapidly in food samples.


fresh meat;fresh-cut lettuce;Escherichia coli;enrichment;PCR


  1. Cebula TA, Payne WL, Feng P. 1995. Simultaneous identification of strains of Escherichia coli serotype O157:H7 and their Shiga-like toxin type by mismatch amplification mutation assay-multiplex PCR. J Clin Microbiol 33:248-250.
  2. Dwivedi HP, Jaykus LA. 2011. Detection of pathogens in foods: The current state-of-the-art and future directions. Crit Rev Microbiol 37:40-63.
  3. Feng P, Stephen D, Weagant SD, Grant GA, Burkhardt W. 2002. Food Drug Administration (FDA)-Bacteriological Analytical Manual (BAM) chapter 4: Enumeration of Escherichia coli and the coliform bacteria. Available from: Accessed at Mar 4, 2018.
  4. Frampton EW, Restaino L. 1993. Methods for Escherichia coli identification in food, water and clinical samples based on beta-glucuronidase detection. J Appl Microbiol 74:223-233.
  5. Gracias KS, McKillip JL. 2004. A review of conventional detection and enumeration methods for pathogenic bacteria in food. Can J Microbiol 50:883-890.
  6. Heidenreich B, Poehlmann C, Sprinzl M, Gareis M. 2010. Detection of Escherichia coli in meat with an electrochemical biochip. J Food Prot 73:2025-2033.
  7. Kim HJ, Ryu JO, Song JY, Kim HY. 2017. Multiplex polymerase chain reaction for identification of Shigellae and four Shigella species using novel genetic markers screened by comparative genomics. Foodborne Pathog Dis 14:400-406.
  8. Li F, Li B, Dang H, Kang Q, Yang L, Wang Y, Aguilar ZP, Lai W, Xu H. 2017. Viable pathogens detection in fresh vegetables by quadruplex PCR. LWT Food Sci Technol 81:306-313.
  9. Molina F, Lopez-Acedo E, Tabla R, Roa I, Gomez A, Rebollo JE. 2015. Improved detection of Escherichia coli and coliform bacteria by multiplex PCR. BMC Biotechnol 15:48.
  10. Rossen L, Norskov P, Holmstrom K, Rasmussen OF. 1992. Inhibition of PCR by components of food samples, microbial diagnostic assays and DNA-extraction solutions. Int J Food Microbiol 17:37-45.
  11. Scheinberg JA, Dudley EG, Campbell J, Roberts B, DiMarzio M, DebRoy C, Cutter CN. 2017. Prevalence and phylogenetic characterization of Escherichia coli and hygiene indicator bacteria isolated from leafy green produce, beef, and pork obtained from farmers’ markets in Pennsylvania. J Food Prot 80:237-244.
  12. Seo YH, Jang JH, Moon KD. 2010. Microbial evaluation of minimally processed vegetables and sprouts produced in Seoul, Korea. Food Sci Biotechnol 19:1283-1288.
  13. Simancas A, Molina F, Tabla R, Roa I, Rebollo JE. 2016. YaiO, a new target for highly specific detection of Escherichia coli by PCR amplification. In Microbes in the spotlight: Recent progress in the understanding of beneficial and harmful microorganisms. Mendez-Vilas A (ed). Brown Walker Press, Boca Raton, FI, USA. p 234.
  14. Stromberg ZR, Lewis GL, Marx DB, Moxley RA. 2015. Comparison of enrichment broths for supporting growth of Shiga toxin-producing Escherichia coli. Curr Microbiol 71:214-219.
  15. Thomas EJ, King RK, Burchak JACK, Gannon VP. 1991. Sensitive and specific detection of Listeria monocytogenes in milk and ground beef with the polymerase chain reaction. Appl Environ Microbiol 57:2576-2580.
  16. Wang Y, Salazar JK. 2016. Culture-independent rapid detection methods for bacterial pathogens and toxins in food matrices. Compr Rev Food Sci Food Saf 15:183-205.
  17. Yang H, Qu L, Wimbrow AN, Jiang X, Sun Y. 2007. Rapid detection of Listeria monocytogenes by nanoparticle-based immunomagnetic separation and real-time PCR. Int J Food Microbiol 118:132-138.


Grant : Cooperative Research Program for Agriculture Science & Technology Development

Supported by : Rural Development Administration