title: Laboratory and pilot-scale dead-end ultrafiltration concentration of sanitizer-free and chlorinated lettuce wash water for improved detection of Escherichia coli O157:H7.
abstract: An automated dead-end (single pass, no recirculation) ultrafiltration device, the Portable Multi-use Automated Concentration System (PMACS), was evaluated as a means to concentrate Escherichia coli O157:H7 from 40 liters of simulated commercial lettuce wash water. The assessment included generating, sieving, and concentrating sanitizer-free lettuce wash water, either uninoculated or inoculated with green fluorescent protein-transformed E. coli O157:H7 at a high (1.00 log CFU/ml) or low (-1.00 log CFU/ml) concentration. Cells collected within the filters were recovered in approximately 400 ml of buffer to create lettuce wash retentates. The extent of concentration was determined by viable plate counts using a medium selective for the transformed E. coli O157:H7. The samples were qualitatively analyzed for E. coli O157:H7 according to the U. S. Food and Drug Administration Bacteriological Analytical Manual enrichment method and with an electrochemiluminescence immunoassay. This concentration method was then evaluated in a pilot-scale production line at Michigan State University using chlorinated (100, 30, and 10 ppm of available chlorine) lettuce wash water. The total PMACS processing times were 82 ± 6 and 65 ± 5 min for sanitizer-free and chlorinated washes, respectively. Overall, E. coli O157:H7 populations were approximately 2 log higher in retentates than in unconcentrated lettuce wash samples. The higher E. coli O157:H7 levels in the retentates enabled cultural and electrochemiluminescence immunoassay detection in some samples when the corresponding lettuce wash samples were negative. When combined with standard and rapid detection methods, the PMACS concentration method may provide a means to enhance pathogen monitoring of produce wash water.
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, ISA2015, Tampa, Florida 33620-7115, USA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Magaña
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, ISA2015, Tampa, Florida 33620-7115, USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Schlemmer
authors.affiliation: Department of Food Science and Human Nutrition, Michigan State University, 469 Wilson Road, East Lansing, Michigan 48824-1225, USA; Department of Food Science and Technology, University of California-Davis, Davis, CA 95616, USA.
authors.forename: Gordon R
authors.initials: GR
authors.lastname: Davidson
authors.affiliation: Department of Food Science and Human Nutrition, Michigan State University, 469 Wilson Road, East Lansing, Michigan 48824-1225, USA.
authors.forename: Elliot T
authors.initials: ET
authors.lastname: Ryser
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 East Fowler Avenue, ISA2015, Tampa, Florida 33620-7115, USA. lim@usf.edu.
authors.forename: Daniel V
authors.initials: DV
authors.lastname: Lim
mesh_terms: D002713:Chlorine / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004202:Disinfectants / Q000494:pharmacology*; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification*; D005506:Food Contamination / Q000032:analysis; D005511:Food Handling / Q000295:instrumentation / Q000379:methods*; D005618:Fresh Water / Q000382:microbiology*; D006801:Humans; D007753:Laboratories; D018545:Lactuca / Q000382:microbiology*; D010865:Pilot Projects; D014462:Ultrafiltration / Q000295:instrumentation / Q000379:methods*; D014481:United States
chemical_list: D004202:Disinfectants; D002713:Chlorine