Factors Affecting Pathogen Survival in Finished Dairy Compost with Different Particle Sizes Under Greenhouse Conditions

Abstract

This study investigated the survival of Escherichia coli O157:H7 and Salmonella Typhimurium in finished dairy compost with different particle sizes during storage as affected by moisture content and temperature under greenhouse conditions. The mixture of E. coli O157:H7 and S. Typhimurium strains was inoculated into the finished composts with moisture contents of 20, 30, and 40%, separately. The finished compost samples were then sieved into 3 different particle sizes (>1000, 500-1000, and <500 μm) and stored under greenhouse conditions. For compost samples with moisture contents of 20 and 30%, the average Salmonella reductions in compost samples with particle sizes of >1000, 500-1000, and <500 μm were 2.15, 2.27, and 2.47 log colony-forming units (CFU) g(-1) within 5 days of storage in summer, respectively, as compared with 1.60, 2.03, and 2.26 log CFU g(-1) in late fall, respectively, and 2.61, 3.33, and 3.67 log CFU g(-1) in winter, respectively. The average E. coli O157:H7 reductions in compost samples with particle sizes of >1000, 500-1000, and <500 μm were 1.98, 2.30, and 2.54 log CFU g(-1) within 5 days of storage in summer, respectively, as compared with 1.70, 2.56, and 2.90 log CFU g(-1) in winter, respectively. Our results revealed that both Salmonella and E. coli O157:H7 in compost samples with larger particle size survived better than those with smaller particle sizes, and the initial rapid moisture loss in compost may contribute to the fast inactivation of pathogens in the finished compost. For the same season, the pathogens in the compost samples with the same particle size survived much better at the initial moisture content of 20% compared to 40%.

Survival of Escherichia coli O157:H7 and Salmonella enterica in animal waste‐based composts as influenced by compost type, storage condition and inoculum level

“…Typhimurium survived in dairy compost with various particle sizes after a 30‐day storage under greenhouse condition (Diao et al . ). And non‐O157 STEC also survived for over 125 days in dairy compost stored at 4 and 22°C (Wang et al .…”

“…However, there are very few studies on the survival of foodborne pathogens in composted or physically heat-treated animal wastes during storage. Our previous studies have showed that E. coli O157:H7 and S. Typhimurium survived in dairy compost with various particle sizes after a 30-day storage under greenhouse condition (Diao et al 2015).…”

Fate of Viable but Non-culturable Listeria monocytogenes in Pig Manure Microcosms

“…In that case, the presence of manure in the soil significantly reduced the survival of the strain of Salmonella at 5°C and 15°C but not at 25°C. Furthermore, characteristics of manure matrix can also contribute to the survival of pathogens as suggested by Diao et al (2015) who observed that temperature, moisture content and particle size of dairy compost affected the survival of E. coli O157:H7 and Salmonella Typhimurium.…”

Persistence and Potential Viable but Non-culturable State of Pathogenic Bacteria during Storage of Digestates from Agricultural Biogas Plants

“…Several abiotic factors can affect the persistence of pathogenic bacteria. The characteristics of manure samples, including temperature, moisture content and particle size, may contribute to the persistence of pathogens ( Ahmed et al, 1995 ; Garcia et al, 2010 ; Diao et al, 2015 ). In this study, the temperature was maintained at 24°C and we focused on such characteristics of the digestates as moisture content, nutrient content, VM and pH.…”

“…Among such physical and chemical properties, volatile acids were not tested in our study, but this factor has been shown to affect the persistence of L. monocytogenes in manure-based compost mixtures of animal origin ( Erickson et al, 2014a ). Characteristics of environmental matrices can thus contribute to the persistence of pathogens, as suggested by Diao et al (2015) . In particular, the effect on the persistence of pathogenic bacteria of biotic factors such as microbial diversity and activity still remains to be explored in treated waste ( Sidhu et al, 2001 ; Paniel et al, 2010 ; Klein et al, 2011 ; Orzi et al, 2015 ).…”