Physical Covering to control Escherichia coli O157:H7 and Salmonella in Static and Windrow Composting Process

Authors: Patel, Jitu; YOSSA, IRENE - Food And Drug Administration(FDA); MACARISIN, DUMITRU - Food And Drug Administration(FDA); Millner, Patricia

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2015
Publication Date: 3/1/2015
Citation: Patel, J.R., Yossa, I., Macarisin, D., Millner, P.D. 2015. Physical Covering to control Escherichia coli O157:H7 and Salmonella in Static and Windrow Composting Process. Applied and Environmental Microbiology. 81:2063-2074.

Interpretive Summary: Compost can be used as a soil amendment for poor soil or as a slow-release fertilizer, a cheaper, sustainable alternative to chemical fertilizers. It also provides other benefits such as increased water retention, improved soil structure and stability, decreased erosion, and a general suppression of plant diseases. During composting, varieties of bacteria break down waste and generate heat, which causes an increase in temperature. High temperatures result in killing of pathogens in compost. We investigated the effect of a 30-cm covering of finished compost on survival of E. coli O157:H7 and Salmonella in static and windrow piles during 84 days of active composting process. Salmonella were reduced significantly within 24 h in windrow piles and were below detection limit after 3 and 7 days at internal locations of windrow and static piles containing finished compost covering, respectively. Likewise, E. coli O157:H7 were undetectable after 1 day in windrow pile covered with finished compost. Use of finished compost as covering significantly increased the number of days =55°C in windrow piles at all locations and in static piles at internal location which resulted in rapid reduction of inoculated pathogens. The sample location significantly influenced survival of E. coli O157:H7 and Salmonella; recovery was lowest at the top location compared to interface locations. Finished compost covering of compost piles aids in reduction of pathogens during the composting process. This information will be usfull to other scientists and the compost industry.

Technical Abstract: This study investigated the effect of 30-cm covering of finished compost on survival of E. coli O157:H7 and Salmonella in active static and windrow composting systems. Feedstock inoculated with E. coli O157:H7 (7.41 log CFU/g) and Salmonella (6.46 log CFU/g) were placed in biosentry tubes (7.5 cm dia x 30 cm) and placed at approximately 10-, 10-, and 30- cm depths beneath the surface at three locations: two sides of interface and internal (top) location of the piles, respectively. Uninoculated feedstock samples for moisture, pH, and total carbon (C) and nitrogen (N) analysis, and a Datalogger for temperature recording were also placed in biosentry tubes. On days 1, 3, 7, 14, 21, 28, 56, and 84, surviving populations of inoculated E. coli O157:H7 and Salmonella, generic E. coli, total and fecal coliforms in compost samples were analyzed. Salmonella were reduced significantly within 24 h in windrow piles and were below detection limit after 3 and 7 days at internal locations of windrow and static piles containing finished compost covering, respectively. Likewise, E. coli O157:H7 were undetectable after 1 day in windrow pile covered with finished compost. Use of finished compost as covering significantly increased the number of days =55°C in windrow piles at all locations and in static piles at internal location which resulted in rapid reduction of inoculated pathogens. Further, the rate of bacterial reduction was rapid in windrow piles. The sample location significantly influenced survival of E. coli O157:H7 and Salmonella;, recovery was the least at top location compared to interface locations. Finished compost covering of compost piles aids in reduction of pathogens during the composting process.