title: Inactivation of Escherichia coli O157:H7 attached to spinach harvester blade using bacteriophage.
abstract: Outbreaks associated with leafy greens have focused attention on the transfer of human pathogens to these commodities during harvest with commercial equipment. Attachment of Escherichia coli O157:H7 on new or rusty spinach harvester blades immersed in spinach extract or 10% tryptic soy broth (TSB) was investigated. Bacteriophages specific for E. coli O157:H7 were evaluated to kill cells attached to blade. A cocktail of five nalidixic acid-resistant E. coli O157:H7 isolates was transferred to 25 mL of spinach extract or 10% TSB. A piece of sterilized spinach harvester blade (2×1") was placed in above spinach extract or 10% TSB and incubated at room (22 °C) or dynamic (30 °C day, 20 °C night) temperatures. E. coli O157:H7 populations attached to blade during incubation in spinach extract or 10% TSB were determined. When inoculated at 1 log CFU/mL, E. coli O157:H7 attachment to blades after 24 and 48 h incubation at dynamic temperature (6.09 and 6.37 log CFU/mL) was significantly higher than when incubated at 22 °C (4.84 and 5.68 log CFU/mL), respectively. After 48 h incubation, two blades were sprayed on each side with a cocktail of E. coli O157-specific bacteriophages before scraping the blade, and subsequent plating on Sorbitol MacConkey media-nalidixic acid. Application of bacteriophages reduced E. coli O157:H7 populations by 4.5 log CFU on blades after 2 h of phage treatment. Our study demonstrates that E. coli O157:H7 can attach to and proliferate on spinach harvester blades under static and dynamic temperature conditions, and bacteriophages are able to reduce E. coli O157:H7 populations adhered to blades.
authors: Environmental and Microbial Food Safety Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705-2350, USA. jitu.patel@ars.usda.gov
authors: Jitendra
authors: J
authors: Patel
authors: Manan
authors: M
authors: Sharma
authors: Patricia
authors: P
authors: Millner
authors: Todd
authors: T
authors: Calaway
authors: Manpreet
authors: M
authors: Singh
mesh_terms: D000383:Agriculture / Q000295:instrumentation*; D001422:Bacterial Adhesion; D001435:Bacteriophages / Q000502:physiology*; D018441:Biofilms; D015169:Colony Count, Microbial; D018556:Crops, Agricultural / Q000737:chemistry / Q000382:microbiology; D019453:Escherichia coli O157 / Q000254:growth & development* / Q000302:isolation & purification / Q000502:physiology / Q000821:virology*; D005516:Food Microbiology; D005517:Foodborne Diseases / Q000517:prevention & control; D050296:Microbial Viability; D010572:Pest Control, Biological / Q000379:methods*; D010936:Plant Extracts; D018515:Plant Leaves / Q000737:chemistry / Q000382:microbiology; D013045:Species Specificity; D018724:Spinacia oleracea / Q000737:chemistry / Q000382:microbiology*; D013696:Temperature; D013997:Time Factors
chemical_list: D010936:Plant Extracts