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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #325210

Title: Reduction of Salmonella populations on cucumber fruit by application of lytic bacteriophages

item Sharma, Manan
item DASHIELL, GWENDOLYN - University Of Maryland Eastern Shore (UMES)
item Handy, Eric
item East, Cheryl - Roberts
item REYNNELLS, RUSSEL - University Of Maryland Eastern Shore (UMES)
item Millner, Patricia
item WHITE, CHANELLE - University Of Maryland Eastern Shore (UMES)
item HASHEM, FAWZY - University Of Maryland Eastern Shore (UMES)
item NYARKO, EDMOND - University Of Delaware
item MICALLEF, SHIRLEY - University Of Maryland
item COLLINS, ALYSSA - Pennsylvania State University

Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: .

Technical Abstract: Background: Foodborne illness outbreaks of Salmonella enterica associated with consumption of cucumbers (Cucumis sativus) in the U.S. in 2014 and 2015 sickened over 1000 people and caused 5 deaths. Whole and fresh-cut cucumbers are susceptible to Salmonella contamination during growing and harvesting. We evaluated the effectiveness of applying lytic bacteriophages, a non-chemical intervention, to reduce Salmonella populations on cucumbers. Methods: Unwaxed cucumbers (greenhouse-grown, ‘Lisboa’ variety, or mini-cucumbers purchased at retail) were inoculated with 5 log CFU/cucumber Salmonella Newport, and then sprayed with 3.2 mL of 9 log PFU/ml SalmoFresh, a Salmonella-specific bacteriophage preparation (phage), or phosphate-buffered saline (control). Whole cucumbers were stored at 10 or 22oC for 7 days. Mini-cucumbers were sliced with a sterile knife to investigate Salmonella transfer to mesocarp, and fresh-cut pieces were stored at 4oC for 2 days. Salmonella populations from whole and fresh-cut cucumbers were recovered on selective media. Three replicates of each trial were conducted, and statistical analysis (Student t-Test) was performed. Results: Populations (log CFU/cucumber) of Salmonella on phage-treated whole cucumbers stored at 10oC were 2.44, 1.72, and 1.56, which were significantly (p < 0.05) lower than those on control-treated cucumbers (4.27, 3.20, and 2.33) on days 0, 1, and 4, respectively. There were no significant differences in Salmonella populations between phage- and control-treatments of a) whole cucumbers at 22oC, or b) fresh-cut cucumbers stored at 4oC. Conclusions: Direct application of lytic bacteriophages (through spraying) to whole cucumbers was more effective in reducing Salmonella populations than indirect transfer of phages (through slicing) to the mesocarp of cucumbers. The greatest reduction in Salmonella populations occurred immediately after spraying phages onto cucumbers.