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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL ECOLOGY AND SAFETY OF FRESH PRODUCE

Location: Environmental Microbial and Food Safety Laboratory

Title: Comparison of microbial methods to detect fecal coliforms, E. coli and Salmonella spp. in finished compost

Authors
item Reynnells, Russell
item Ingram, David
item Roberts, Cheryl
item Stonebraker, Richard
item Millner, Patricia
item Sharma, Manan

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 22, 2013
Publication Date: N/A

Technical Abstract: Introduction: Compost provides nutrients for produce crops. Improperly composted feedstocks can harbor pathogens which can be transferred to produce crops. The US Environmental Protection Agency (EPA) and US Composting Council (USCC) provide methods to test biosolids and compost, respectively, for fecal coliforms, E. coli, and Salmonella spp. Purpose: To compare existing EPA and USCC methods for the recovery of low levels of fecal coliforms, E. coli, and Salmonella spp. from composts containing a variety of feedstocks (biosolids, manure, and/or yard wastes). Methods: Twenty-nine USCC-certified compost samples were collected from across the United States. Salmonella spp. and non-pathogenic E. coli were inoculated into three 400g aliquots from each sample at 10^1-2 cfu/g. Each inoculated aliquot was processed using EPA Method 1680 (fecal coliforms), EPA Method 1682 (Salmonella spp.), TMECC Method 0701 (fecal coliforms and generic E. coli), and TMECC Method 0702 (Salmonella spp.). Results: Statistical significance was reported using alpha = 0.10. EPA methods had significantly higher recovery efficiencies (RE) of E. coli (p<0.0001) and Salmonella spp. (p=0.0596) than USCC methods from biosolids composts, and for E. coli (p=0.0318) from manure composts. Both methods had statistically equivalentl REs of Salmonella and E. coli from manure and yard waste composts (E. coli (p=0.5164) and Salmonella (p=0.6738). EPA methods had a significantly higher RE of E. coli from biosolids compost compared to RE for yard waste composts. USCC had significantly higher RE for E. coli (p=0.0187) and Salmonella (p=0.0975) from yard waste composts compared to those from biosolids or manure composts. Significance: Overall, EPA methods were more efficient in recovering low levels of both Salmonella and E. coli across all compost types compared to USCC methods. USCC methods were consistently more likely to have higher RE of target organisms from yard waste composts compared to manure or biosoids composts.

Last Modified: 10/25/2014