Potential transfer of Salmonella to cutting blade during spinach harvesting operation

Authors: Adeeb, Shanta; Patel, Jitu; Sharma, Manan; Millner, Patricia

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/2009
Publication Date: 4/15/2009
Citation: Adeeb, S.L., Patel, J.R., Sharma, M., Millner, P.D. 2009. Potential transfer of Salmonella to cutting blade during spinach harvesting operation. BARC Poster Day Abstract Book.

Interpretive Summary:

Technical Abstract: Outbreaks of Salmonellosis from the consumption of produce have often been reported. Produce such as tomatoes, lettuce, peppers and cantaloupes have been implicated in outbreaks of Salmonellosis in the United States. Recent S. saintpaul outbreak associated with raw tomatoes resulted in 1442 cases of infections in 43 states, the District of Columbia, and Canada. Outbreaks associated with leafy greens have focused attention on the transfer of human pathogens to leafy greens during mechanical harvesting. Harvesting of baby spinach presents an opportunity for contaminated blades to transfer bacterial foodborne pathogens to recently harvested spinach. Biofilm forming ability of Salmonella on harvester blades immersed in spinach extract was studied. Individual cocktails of five Salmonella isolates isolates were prepared. Twenty-five ml of spinach extract were inoculated with either Salmonella cocktail at inoculum levels of 1 (low) or 4 (high) log CFU/ml. A sterilized spinach harvester blade (2x1”) was placed in inoculated extract and incubated at room (22 deg C) or dynamic temperature (30 deg C-day, 20 deg C-night) for up to 48 h. At specific times, 2 blades at each inoculum level were analyzed for Salmonella populations. Populations in biofilms were determined by scraping the blade with a Teflon spatula, followed by spiral plating on XLT4 media. Typical Salmonella colonies were counted after 24 h incubation at 37 deg C. The adherence of Salmonella to blade varied (P<0.05) with incubation temperature and incubation time. Salmonella populations recovered from blades inoculated with 4 log CFU/ml following 24 and 48 h incubation at static temperature (6.20 and 5.72 log CFU/ml) were significantly higher than those populations recovered at dynamic temperature (3.97 and 3.68 log CFU/ml), respectively. Biofilms were formed by Salmonella on harvester blades under both static and dynamic temperatures. Effective cleaning to remove pathogens adhered to harvesting equipment would help prevent potential cross contamination with these pathogens during spinach harvest.