Salmonella Survival in Manure‐Treated Soils during Simulated Seasonal Temperature Exposure

Abstract

Addition of animal manure to soil can provide opportunity for Salmonella contamination of soil, water, and food. This study examined how exposure of hog manure-treated loamy sand and clay soils to different simulated seasonal temperature sequences influenced the length of Salmonella survival. A six-strain cocktail of Salmonella serovars (Agona, Hadar, Heidelberg, Montevideo, Oranienburg, and Typhimurium) was added to yield 5 log cfu/g directly to about 5 kg of the two soils and moisture adjusted to 60 or 80% of field capacity (FC). Similarly, the Salmonella cocktail was mixed with fresh manure slurry from a hog nursery barn and the latter added to the two soils at 25 g/kg to achieve 5 log cfu/g Salmonella. Manure was mixed either throughout the soil or with the top kilogram of soil and the entire soil volume was adjusted to 60 or 80% FC. Soil treatments were stored 180 d at temperature sequences representing winter to summer (-18, 4, 10, 25 degrees C), spring to summer (4, 10, 25, 30 degrees C), or summer to winter (25, 10, 4, -18 degrees C) seasonal periods with each temperature step lasting 45 d. Samples for Salmonella recovery by direct plating or enrichment were taken at 0, 7, and 15 d post-inoculation and thereafter at 15-d intervals to 180 d. Salmonella numbers decreased during application to soil and the largest decreases occurred within the first week. Higher soil moisture, manure addition, and storage in the clay soil increased Salmonella survival. Salmonella survived longest (> or = 180 d) in both soils during summer-winter exposure but was not isolated after 160 d from loamy sand soil exposed to other seasonal treatments. For all but one treatment decimal reduction time (DRT45d) values calculated from the first 45 d after application were < or = 30 d and suggested that a 30-d delay between field application of manure in the spring or fall and use of the land would provide reasonable assurance that crop and animal contamination by Salmonella would be minimized.

Differential interaction of Salmonella enterica serovars with lettuce cultivars and plant-microbe factors influencing the colonization efficiency

“…However, the difference between the serovars in apparent lettuce colonization might be partially determined by the survival of the different S. enterica serovars in manure-amended soil. S. enterica serovars were found to remain viable for at least several months even though a decline was observed (as expected) (Holley et al, 2006). Especially, in the first weeks after inoculation of S. enterica into the manure prior mixing with soil, no significant difference in survival rate (that is decline in viable cell numbers) between S. enterica serovars is expected.…”

Assessment of the content of heavy metals and potential pathogenic microorganisms in soil under illegal dumping sites

“…Salmonella bacteria occurred only in the soil at C landfill at 25 MPN g -1 . According to Holley et al (2006), bacilli of Salmonella spp. survival in soil range from 6 to several hundred days, which create a real risk for soil contamination and for the growing plants.…”

Risk Factors Associated with Salmonella and Listeria monocytogenes Contamination of Produce Fields

“…Application of manure was also identified as a significant factor that increased the odds of both Salmonella and L. monocytogenes isolation in fields. Numerous studies (37,39,41,(57)(58)(59)(60)(61)(62)(63)(64) have demonstrated that the application of manure to soils can introduce pathogens and may facilitate long-term persistence of pathogens in soil. One study observed Salmonella to persist in manure, manure-amended nonsterilized soil, and manure-amended sterilized soil for 184, 332, and 405 days, respectively (60).…”