Human enteric bacteria transmission to leafy greens by flies
J. TALLEY (1), R. Pace (1), A. Wayadande (1). (1) Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, U.S.A.
Synanthropic flies are known mechanical vectors of human pathogens, primarily in hospital and restaurant settings. However, the role of flies in transmission of pathogenic bacteria to food crops is largely unknown. Using blow flies, <i>Phormia regina</i>, and house flies, <i>Musca domestica</i>, vector competence and the transmission parameters of two GFP-tagged bacteria, <i>Escherichia coli</i> O157:H7 and <i>Salmonella enterica</i> was tested. Adult flies were given access to cow manure inoculated with 10<sup>6</sup> cfus/gr <i>E. coli</i>, <i>Salmonella</i>, or buffer control, then transferred to lettuce plants. Plants were homogenized and 100 ul aliquots plated on selective media. Analysis of recovered GFP-expressing colonies revealed that house flies and blow flies transferred more <i>E. coli</i> O157:H7 to lettuce than <i>S. enterica</i>. Blow flies were also tested for acquisition of each pathogen per unit time. Flies were given precise 10 sec and 30 sec acquisitions on manure contaminated with bacteria or control buffer, then homogenized and plated as above. Blow flies acquired significantly more <i>E. coli</i> O137:H7 than <i>S. enterica</i>, regardless of acquisition time. When pathogen-exposed blow flies were given two 30 second inoculation periods on lettuce discs, flies deposited approximately the same number of <i>E. coli</i> O157:H7 cells as <i>S. enterica</i> cells. These data suggest greater <i>E. coli</i> adhesion to fly tarsi and mouthparts compared to <i>Salmonella</i>, but equal release rates to the lettuce surface for the two pathogens.
View Presentation |
