Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2015
Publication Date: 5/30/2015
Citation: Roberts, B.N., McLaughlin, M.R., Brooks, J.P. 2015. Effects of climate variability on bacterial pathogen decay in spinach bed macrocosms (abstract). American Society of Microbiology Conference Proceedings, May 30-June 2, 2015, New Orleans, LA.
Technical Abstract: Background: It is estimated that 47.8 million people contract foodborne pathogens each year. Understanding the risk of foodborne pathogens and their ability to survive on or near food crops is of great concern. Current pathogen decay rates are limited due to environmental variability. With a changing climate, it is imperative to predict inactivation rates based on climate extremes, and whether these promote or inhibit pathogen colonization. Method: This study investigates the impact of climate variability on the inactivation of Salmonella, Listeria and E. coli O157 inoculated in bovine feces placed in spinach (Spinacia oleracea) bed macrocosms. Several models have been proposed to predict environmental changes due to the effects of anthropogenic activities; these proposed models have been used to set macrocosm climates and moisture content. Three watering intensities (high, normal, low), two temperatures (25oC, 30oC) and pathogen soil-spatial factor (spinach rhizosphere, furrow) were analyzed to determine the effects on pathogen inactivation. Each bacterium was inoculated in 10 g of cattle manure at 106 cfu g-1 and placed near the spinach rhizosphere and furrow at the top 4 cm of soil. Using selective medium, each bacterium was evaluated over a 6-week period to determine the decline in levels of fecal bound bacteria. Results: During the 6 weeks of spinach growth, Salmonella and E. coli O157 declined 2 -3 log10 and Listeria declined 4-5.5 log10. Inactivation of E. coli O157, and Listeria, Salmonella was slower in lower temperatures but only E. coli O157 was significant. Fecal location was significant in the inactivation of Listeria where the furrow offered a slower decay but was not significant for E. coli O157 and Salmonella. Watering intensity of spinach macrocosms did affect fecal bound bacteria inactivation but not significantly for any bacteria studied. Conclusion: This study gives insight into the effect of climate variability on pathogen inactivation rates near spinach which will be used to drive future quantitative microbial risk analyses. Understanding how extreme climate variances alter bacterial decay will provide useful data to promote safe food crops, to help reduce economic losses and to prevent public health risks.