Assessment of vermicompost compositions containing cattle, sheep, and poultry manures for contamination risk of microgreens by foodborne pathogens

Abstract

Transfer of pathogens to microgreens may occur due to the use of contaminated materials used during growth. The aim of this study was to assess contamination risk of microgreens from solid and vermicompost (extract) tea compositions containing cattle, sheep, and poultry manures. Pasteurized vermicompost compositions and non-aerated vermicompost teas were produced with composted cattle, sheep, and poultry feces. Separate ampicillin (Amp) resistant cocktails (3-strains/cocktail) of Escherichia coli O157:H7 and Salmonella enterica and non-resistant Listeria monocytogenes were inoculated (10(5)-10(7) CFU/g) into solid vermicompost and vermicompost tea for storage at room temperature up to 28 days. Radish microgreens were grown in vermicompost and in inoculated perlite mixture (1:1) and diluted (1:1) vermicompost tea-soaked perlite as soilless substrate (n = 4). Pathogen persistence was not affected by vermicompost compositions made of different animal manures (P > 0.05). Similar survival trends were observed for E. coli O157:H7 and S. enterica in all vermicompost samples. Over the 28-day storage, E. coli O157:H7 and S. enterica populations declined between 4.5 and 5.7 log CFU/g in solid vermicompost compositions, and 3.9 and 5.9 log CFU/g in prepared vermicompost teas, respectively (P <= 0.05). Reduction in L. monocytogenes populations were <= 1.8 log CFU/g in all vermicompost preparations. Pathogen populations transferred to microgreens from vermicompost and perlite mixture and vermicompost tea-soaked perlite ranged from 5.6 +/- 1.0 to 7.1 +/- 0.1 log CFU/g. The use of contaminated or inadequately pasteurized solid vermicompost and derived vermicompost teas made of animal feces could pose a high risk for contamination of microgreens.