title: Decay rates of zoonotic pathogens and viral surrogates in soils amended with biosolids and manures and comparison of qPCR and culture derived rates.
abstract: OBJECTIVE
  The purpose of this study was to establish inactivation decay constants of foodborne pathogens and coliphage in clay and sandy soils for future "downstream" analyses such as quantitative microbial risk analysis and to compare cultivation-dependent and -independent (e.g. qPCR) methods.
  
  
  RESULTS
  Salmonella enterica, Campylobacter jejuni, Listeria monocytogenes, Escherichia coli O157:H7, and Clostridium perfringens, were seeded together with MS2 and ØX174 phages, into three waste matrices (Class B biosolids, swine lagoon effluent, cattle manure), and phosphate buffered saline (PBS) as a control, and applied to two soil types (sandy loam, clay loam) using two management practices (incorporated, surface applied). S. enterica and L. monocytogenes inactivation rates were positively affected (e.g. slower rate) by solid wastes, while C. jejuni was quickly inactivated by day 7 regardless of waste type. The use of qPCR provided more conservative inactivation rates, with qPCR-based rates typically twice as slow as cultivation-based. The effect of soil type and management were less apparent as rates were variably affected. For instance, incorporation of waste negatively impacted (e.g. faster rate) inactivation of Salmonella when measured by qPCR, while the opposite was true when measured by cultivation. Inactivation rates were organism∗waste∗soil∗management dependent since the interactions of these main effects significantly affected most combinations.
  
  
  CONCLUSIONS
  Class B biosolids and cattle manure most often slowed inactivation when measured by cultivation, but the complex interactions between variables and organism made sweeping conclusions difficult. On the contrary cultivation-independent inactivation rates were negatively affected by solid wastes. Inactivation rates developed by cultivation-dependent and -independent assays needs further scrutiny as interprerations can vary by orders of magnitude depending on the organism∗environment combination.
  
  
  CONCLUSIONS
  This study compares decay rate data based on waste, soil, management and assay type which can be further used in risk assessments.
authors: Agriculture Research Service, United States Department of Agriculture, Mississippi State, MS 39762, USA. Electronic address: bnh3@msstate.edu.
authors: B N
authors: BN
authors: Roberts
authors: Pathobiology and Population Medicine Department, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
authors: R H
authors: RH
authors: Bailey
authors: Agriculture Research Service, United States Department of Agriculture, Mississippi State, MS 39762, USA.
authors: M R
authors: MR
authors: McLaughlin
authors: Agriculture Research Service, United States Department of Agriculture, Mississippi State, MS 39762, USA.
authors: J P
authors: JP
authors: Brooks
mesh_terms: D000818:Animals; D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D002417:Cattle; D015169:Colony Count, Microbial / Q000379:methods*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D008372:Manure / Q000382:microbiology*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D013552:Swine; D014780:Viruses / Q000378:metabolism; D014865:Waste Disposal, Fluid
chemical_list: D008372:Manure; D012987:Soil
keywords: Campylobacter; Clostridium perfringens; E. coli O157:H7; Land application; Listeria; MS2; Salmonella; biosolids; manure; waste; ØX174