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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Food and Feed Safety Research » Research » Publications at this Location » Publication #333083
Research Project: Identification of the Ecological Niches and Development of Intervention Strategies to Reduce Pathogenic Foodborne Pathogens in Poultry

Location: Food and Feed Safety Research

Title: Filth fly transmission of Escherichia coli O157:H7 and Salmonella enterica to lettuce, Lactuca sativa

Author
item PACE, REBECCA - Oklahoma State University
item TALLEY, JUSTIN - Oklahoma State University
item Crippen, Tawni - Tc
item WAYADANDE, ASTRI - Oklahoma State University

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2016
Publication Date: 1/11/2017
Citation: Pace, R.C., Talley, J.L., Crippen, T.L., Wayadande, A.C. 2017. Filth fly transmission of Escherichia coli O157:H7 and Salmonella enterica to lettuce, Lactuca sativa. Annals of the Entomological Society of America. 110(1):83-89.

Interpretive Summary: Filth flies have been implicated in the dispersal of human disease pathogens. The ability of the black blow fly and the house fly to acquire and transfer bacteria onto baby lettuce leaves was compared. The flies were exposed to a tagged E. coli O157:H7 or Salmonella enterica in manure for one hour, then allowed access to lettuce plants overnight. The presence of bacteria on the plants and flies was then assessed. Tagged bacterial colonies were counted, then confirmed by molecular means. While blow flies picked up significantly more E. coli O157:H7 than did house flies, there was not a major difference between the bacterial amounts deposited onto the lettuce. There was no significant difference in the amount of Salmonella picked up by the two fly species; however, blow flies deposited significantly more Salmonella onto lettuce than did house flies. To more accurately assess attachment and release of bacteria, flies were given precisely timed exposure and deposition periods. Individual flies were exposed to tagged bacteria in manure for 10 and 30 second periods. Blow flies acquired more E. coli O157:H7 than Salmonella in the both time periods. Flies exposed to manure for 10 and 30 s were then tested for deposition by forcing the flies to walk on lettuce leaves. While house flies have historically been implicated in the transmission of human pathogens to food, the data presented suggests that blow flies are more efficient vectors of E. coli O157:H7 and Salmonella to leafy greens than house flies.

Technical Abstract: Filth flies have been implicated in the dispersal of human disease pathogens; however, fly transmission parameters of human pathogens to plants are largely undescribed. The capacity of the black blow fly, Phormia regina, to acquire and subsequently release bacteria onto baby lettuce leaves was compared to the house fly, Musca domestica. Adult P. regina and M. domestica were exposed to GFP-tagged E. coli O157:H7 or S. enterica inoculated manure for one hour, then allowed access to lettuce plants overnight. The presence of bacteria on the plants and flies was then measured by standard microbiological methods. GFP-expressing colonies were counted, and polymerase chain reaction was used to confirm the identity of fluorescing bacteria. While blow flies acquired significantly more E. coli O157:H7 than did house flies, there was not a significant difference between the depositions of bacteria on the lettuce. Conversely, there was no significant difference in the acquisition of S. enterica by the two fly species; however, blow flies deposited significantly more S. enterica onto lettuce than did house flies. Therefore, to more accurately assess attachment and release of bacteria, flies were given precisely timed exposure and inoculation periods. Individual flies were exposed to GFP-tagged E. coli O157:H7 or S. enterica inoculated manure for 10 and 30 second periods. Blow flies acquired more E. coli O157:H7 than S. enterica in the both time periods. Flies exposed to manure for 10 and 30 s were then tested for deposition by forcing the flies to walk on lettuce leaves. Blow flies deposited comparable amounts of E. coli O157:H7 and S. enterica. House flies have historically been implicated in the transmission of human pathogens to food. The data presented suggests that blow flies are more efficient vectors of E. coli O157:H7 and S. enterica to leafy greens than house flies.