RECOVERY OF ESCHERICHIA COLI O157:H7 FROM FIBER OPTIC WAVEGUIDES USED FOR RAPID BIOSENSOR DETECTION

Abstract

Consumption of ground beef has been implicated in the majority of outbreaks of disease from Escherichia coli O157:H7. There is a great need for rapid, sensitive, and specific microbial detection and isolation methods for the detection and recovery of pathogens such as E. coli O157:H7. Evanescent wave, fiber optic biosensors are an innovative, cutting‐edge technology with the potential to meet such a need. Food pathogens such as E. coli O157:H7 can be detected in minutes using the biosensor assay rather than days using conventional methods. The biosensor assay is sensitive and presently has the ability to directly detect 102 CFU of E. coli O157:H7 in E. coli O157:H7‐seeded PBS or ground beef. In this study, it was determined that once the pathogen had been positively identified, it could then be recovered by culturing the cells captured on the waveguide used in the biosensor assay. E. coli O157:H7‐seeded PBS or ground beef samples were assayed using an evanescent wave, fiber optic biosensor. After a positive identification on the biosensor, the waveguide was added to modified LB medium supplemented with 10 μg/mL acriflavin (mLB) and incubated at 42C for a minimum of 4 h followed by selection on Rainbow O157 agar incubated 16 to 18 h at 37C. E. coli O157:H7 was confirmed using agglutination with E. coli O157:H7 antiserum. It was possible to recover E. coli O157:H7 colonies in E. coli O157:H7‐seeded PBS or ground beef when 1 mL samples containing at least 2.0 × 103 CFU of E. coli O157:H7 had been injected into the biosensor. It took only 24 h to detect the target pathogen, recover the pathogen from the sample, and grow isolated colonies. This total time included sample preparation, detection, enrichment culture, and growth of cells to produce isolated colonies on a selective and differential medium. The identification of isolated colonies was then quickly confirmed using slide agglutination with the appropriate antiserum. This method significantly improved the speed of the confirmation of the presence of the pathogen and of the isolation of the pathogen, from 4 days using conventional methods to one day using the biosensor assay.