Importance of soil amendments: survival of bacterial pathogens in manure and compost used as organic fertizliers

Authors: Sharma, Manan; REYNNELLS, RUSSELL - University Of Maryland Eastern Shore (UMES)

Submitted to: Microbiology Spectrum
Publication Type: Review Article
Publication Acceptance Date: 9/3/2015
Publication Date: 8/5/2016
Publication URL: http://handle.nal.usda.gov/10113/5399131
Citation: Sharma, M., Reynnells, R. 2016. Importance of soil amendments: survival of bacterial pathogens in manure and compost used as organic fertizliers. Microbiology Spectrum. 4:1-13.

Interpretive Summary: Biological soil amendments (BSA’s) like manure and compost can be nutrient-rich fertilizers for the cultivation of fruit and vegetable crops. However, animal manures are known to harbor enteric pathogens which can be transferred to fruits and vegetables, potentially leading to cases of foodborne illness through the consumption of contaminated produce. Under certain conditions pathogens have been shown to regrow and resuscitate in both manure-amended soils and compost. Other studies have indicated that manure application may lead to the introduction of bacteria harboring antibiotic-resistant genes to soils. The physicochemical characteristics (moisture content, type of soils, type of animal manure used) of the manure and soil affects the survival and potential regrowth of these pathogens in BSA’s. In some cases bacterial pathogens, may adapt to conditions in manure or compost-amended soils, extending their potential survival in these environments. In the United States there are several commodity-specific, current and proposed federal rules which provide guidance on the application of BSA’s as fertilizers to soils. Several of these guidelines and rules require an interval between the application of manure to soils and harvest to minimize the transfer of pathogens to fruits and vegetables. Overall, biological soil amendments applied as fertilizers to soils can support the survival and regrowth of pathogens. BSA’s should be handled and applied in a manner which reduces the prevalence of pathogens in soils and likelihood of transfer of foodborne pathogens to fruits and vegetables.

Technical Abstract: Biological soil amendments (BSA’s) like manure and compost are frequently used as organic fertilizers to soils to improve its physical and chemical properties. However, BSAs have been known to be a reservoir for enteric bacterial pathogens like enterohemorrhagic E. coli, Salmonella spp, and Listeria spp. There are numerous mechanisms for manure to transfer pathogens to growing fruits and vegetables, and several outbreaks of infections have been linked to manure-related contamination of leafy greens. In the United States there are several commodity-specific, current and proposed federal rules which provide guidance on the application of BSA’s as fertilizers to soils, some of which require an interval between the application of manure to soils and the harvest of fruits and vegetables. The work presented here reviews the survival, persistence, and regrowth/ resuscitation of bacterial pathogens in manure, biosolids, and composts. Moisture, along with climate and physicochemical properties of soil, manure, or compost, play a significant role in the ability pathogens to persist and resuscitate in amended soils. Adaptation of enteric bacterial pathogens may also extend their persistence in manure- or compost-amended soils. The presence of antibiotic resistance genes in soils may also be increased by manure application. Overall, biological soil amendments applied as fertilizers to soils can support the survival and regrowth of pathogens. BSA’s should be handled and applied in a manner which reduces the prevalence of pathogens in soils and likelihood of transfer of foodborne pathogens to fruits and vegetables.