Automated dead-end ultrafiltration for concentration and recovery of total coliform bacteria and laboratory-spiked Escherichia coli O157:H7 from 50-liter produce washes to enhance detection by an electrochemiluminescence immunoassay.

An automated concentration system (ACS) based on dead-end ultrafiltration was used in this study to concentrate bacteria, including Escherichia coli O157:H7, from 50-liter produce washes (PWs, sieved produce wash). Cells trapped in the filters were recovered in approximately 400 ml of buffer to create PW retentates (PWRs). Extent of concentration was determined by analyzing PWs and PWRs for total coliform bacteria and E. coli O157:H7 using standard methods. In addition, an electrochemiluminescence immunoassay was evaluated for detection of E. coli O157:H7 in spiked PWs and PWRs to demonstrate usefulness of the ACS for same-day detection. The levels of total coliform bacteria and E. coli O157:H7 in PWRs were higher than those in PWs by 1.85 ± 0.41 log most probable number per 100 ml and 1.82 ± 0.24 log CFU/ml, respectively. Electrochemiluminescence detection of E. coli O157:H7 was accomplished within 2 h using ACS concentration of lettuce and spinach wash water artificially spiked with the pathogen at levels as low as 0.36 log CFU/ml and 1.39 log CFU/ml, respectively. Detection of E. coli O157:H7 at -0.93 ± 0.15 log CFU/ml in lettuce wash occurred within approximately 6 h when a 4-h enrichment step was added to the procedure. Use of dead-end ultrafiltration increased bacterial concentrations in PWR and allowed same-day detection of low levels of E. coli O157:H7 in PW. This concentration system could be useful to improve the sensitivity of current rapid methods for detection of low levels of foodborne pathogens in PW water.

[1]  T. Suslow,et al.  Comparative evaluation of practical functionality of rapid test format kits for detection of Escherichia coli O157:H7 on lettuce and leafy greens. , 2009, Journal of food protection.

[2]  James P. Nataro,et al.  Diarrheagenic Escherichia coli , 1998, Clinical Microbiology Reviews.

[3]  V. Hill,et al.  Dead-End Hollow-Fiber Ultrafiltration for Recovery of Diverse Microbes from Water , 2009, Applied and Environmental Microbiology.

[4]  D. Lim,et al.  Automated concentration and recovery of micro‐organisms from drinking water using dead‐end ultrafiltration , 2008, Journal of applied microbiology.

[5]  D. Lim,et al.  Rapid dead-end ultrafiltration concentration and biosensor detection of enterococci from beach waters of Southern California. , 2009, Journal of water and health.

[6]  P. J. Stephens,et al.  Direct inoculation into media containing bile salts and antibiotics is unsuitable for the detection of acid/salt stressed Escherichia coli O157:H7 , 1998, Letters in applied microbiology.

[7]  P. J. Stephens,et al.  An improved direct plate method for the enumeration of stressed Escherichia coli O157:H7 from food. , 1998, Journal of food protection.

[8]  K. Warriner,et al.  Concentration and detection of Salmonella in mung bean sprout spent irrigation water by use of tangential flow filtration coupled with an amperometric flowthrough enzyme-linked immunosorbent assay. , 2009, Journal of food protection.

[9]  Lee-Ann Jaykus,et al.  A field study of the microbiological quality of fresh produce. , 2005, Journal of food protection.

[10]  Barry S. Michaels,et al.  Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 4. Infective doses and pathogen carriage. , 2008, Journal of food protection.

[11]  B. Marks,et al.  A mathematical risk model for Escherichia coli O157:H7 cross-contamination of lettuce during processing. , 2011, Food microbiology.

[12]  Daniel V. Lim,et al.  Same-Day Detection of Escherichia coli O157:H7 from Spinach by Using Electrochemiluminescent and Cytometric Bead Array Biosensors , 2010, Applied and Environmental Microbiology.

[13]  Gwangpyo Ko,et al.  Hollow-fiber ultrafiltration for the concentration and simultaneous recovery of multiple pathogens in contaminated foods. , 2009, Journal of food protection.

[14]  Jothikumar Narayanan,et al.  Ultrafiltration-based techniques for rapid and simultaneous concentration of multiple microbe classes from 100-L tap water samples. , 2008, Journal of Microbiological Methods.

[15]  Guobao Xu,et al.  Applications and trends in electrochemiluminescence. , 2010, Chemical Society reviews.

[16]  L. Jaykus,et al.  Detection of pathogens in foods: the current state-of-the-art and future directions , 2011, Critical reviews in microbiology.

[17]  Darrell W. Donahue,et al.  Methods for rapid separation and concentration of bacteria in food that bypass time-consuming cultural enrichment. , 2003, Journal of food protection.

[18]  J. Bruno,et al.  Sensitive detection of biotoxoids and bacterial spores using an immunomagnetic electrochemiluminescence sensor. , 1995, Biosensors & bioelectronics.

[19]  Adopted March,et al.  Response to questions posed by the food safety and inspection service regarding determination of the most appropriate technologies for the food safety and inspection service to adopt in performing routine and baseline microbiological analyses. , 2010, Journal of food protection.

[20]  Stephaney D. Leskinen,et al.  Rapid Ultrafiltration Concentration and Biosensor Detection of Enterococci from Large Volumes of Florida Recreational Water , 2008, Applied and Environmental Microbiology.

[21]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .