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Use of tools of biotechnology to address questions of virulence and survival of foodborne pathogensThrough support from USDA grants we are addressing the role that fertilization with manure may play in the contamination of fresh produce and about the extent to which contamination can arise from irrigation with contaminated water. This project complements an additional project addressing the microbial safety of alfalfa sprouts. We utilize marker bacteria expressing green fluorescent protein (GFP) to study behavior of bacteria in plants and other food matrix's. Marker bacteria are visualized using fluorescence microscopy and images captured with a CCD camera. Alfalfa seeds are contaminated with marker bacteria. germinated. and sprouts grown to maturity in specially constructed chambers. The sprouts are harvested and processed for imaging to determine spatial location of marker bacteria. Research investigating membrane vesicles released by E. coli O157:H7 lead to the discovery that such vesicles contain chromosomal. plasmid. and phage DNA. Although other researchers have demonstrated vesicles contain DNA. and that DNA can be transferred: transformation and expression has not been demonstrated previously. Our research demonstrates that shiga toxin is not only produced. but expressed in an active form based on verocytotoxicity studies. Microorganisms use many methods to ensure their survival including entering a viable but non-culturable state to prolong survival under adverse growth conditions. We demonstrate E. coli O157:H7 enter the VNC state. alone this finding is significant. However. our research demonstrates that E. coli O157:H7 do not enter the VNC state in ground beef . but can exist in the VNC state in ground beef. Finally. as stated we are interested in development of methods for identifying foodborne pathogens. Currently we are developing an RT-PCR assay for screening samples for the presence of only viable E. coli O157:H7 in food samples. The assay is particularly beneficial for detecting cells. which grow poorly or not at all when standard growth conditions are used. View Dr. Matthews' publications in Pub Med |
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