Modeling the contamination of lettuce with Escherichia coli 157:H7 from manure-amended soil and the effect of intervention strategies
Franz, E. ; Semenov, A.V. ; Bruggen, A.H.C. van - \ 2008
Journal of Applied Microbiology 105 (2008)5. - ISSN 1364-5072 - p. 1569 - 1584.
quantitative risk-assessment - enterica serovar typhimurium - waste-water reclamation - treated sewage-sludge - virus monitoring data - dutch dairy farms - in-ground beef - irrigation water - leaf lettuce - cattle feces
Aims: A growing number of foodborne illnesses has been associated with the consumption of fresh produce. In this study, the probability of lettuce contamination with Escherichia coli O157:H7 from manure-amended soil and the effect of intervention strategies was determined. Methods and Results: Pathogen prevalence and densities were modelled probabilistically through the primary production chain of lettuce (manure, manure-amended soil and lettuce). The model estimated an average of 0·34 contaminated heads per hectare. A minimum manure storage time of 30 days and a minimum fertilization-to-planting interval of 60 days was most successful in reducing the risk. Some specific organic farming practices concerning manure and soil management were found to be risk reducing. Conclusions: Certain specific organic farming practices reduced the likelihood of contamination. This cannot be generalized to organic production as a whole. However, the conclusion is relevant for areas like the Netherlands where there is high use of manure in both organic and conventional vegetable production. Significance and Impact of the Study: Recent vegetable-associated disease outbreaks stress the importance of a safe vegetable production chain. The present study contributed to this by providing a first estimate of the likelihood of lettuce contamination with E. coli O157:H7 and the effectiveness of risk mitigation strategies
Prevalence of shiga toxin-producing Escherichia coli stx1, stx2, eaeA, and rfbE genes and survival of E. coli O157:H7 in manure from organic and low-input conventional dairy farms
Franz, E. ; Klerks, M.M. ; Vos, O.J. de; Termorshuizen, A.J. ; Bruggen, A.H.C. van - \ 2007
Applied and Environmental Microbiology 73 (2007)7. - ISSN 0099-2240 - p. 2180 - 2190.
real-time pcr - enterica serovar typhimurium - gradient gel-electrophoresis - polymerase-chain-reaction - salmonella-enterica - thermal inactivation - contaminated manure - irrigation water - ribosomal-rna - cattle feces
Manure samples were collected from 16 organic (ORG) and 9 low-input conventional (LIC) Dutch dairy farms during August and September 2004 to determine the prevalence of the STEC virulence genes stx(1) (encoding Shiga toxin 1), stx(2) (encoding Shiga toxin 2), and eaeA (encoding intimin), as well as the rfbE gene, which is specific for Escherichia coli O157. The rfbE gene was present at 52% of the farms. The prevalence of rfbE was higher at ORG farms (61%) than at LIC farms (36%), but this was not significant. Relatively more LIC farms were positive for all Shiga toxin-producing E. coli (STEC) virulence genes eaeA, stx(1), and stx(2), which form a potentially highly virulent combination. Species richness of Enterobacteriaceae, as determined by DGGE, was significantly lower in manure positive for rfbE. Survival of a green fluorescent protein-expressing E. coli O157:H7 strain was studied in the manure from all farms from which samples were obtained and was modeled by a biphasic decline model. The time needed to reach the detection limit was predominantly determined by the level of native coliforms and the pH (both negative relationships). Initial decline was faster for ORG manure but leveled off earlier, resulting in longer survival than in LIC manure. Although the nonlinear decline curve could theoretically be explained as the cumulative distribution of an underlying distribution of decline kinetics, it is proposed that the observed nonlinear biphasic pattern of the survival curve is the result of changing nutrient status of the manure over time (and thereby changing competition pressure), instead of the presence of subpopulations differing in the level of resistance.
Explorative research into quality of slurry manure from dairy farms with different feeding strategies
Reijs, J.W. ; Meijer, W.H. ; Bakker, E.J. ; Lantinga, E.A. - \ 2003
Netherlands Journal of Agricultural Science 51 (2003)1-2. - ISSN 0028-2928 - p. 67 - 89.
rundveemest - rundveedrijfmest - stikstof - diervoedering - grasbestand - fytotoxiciteit - grassen - klavers - biotesten - melkveehouderij - cattle manure - cattle slurry - nitrogen - animal feeding - herbage - phytotoxicity - grasses - clovers - bioassays - dairy farming - cress lepidium-sativum - seed-germination - sewage-sludge - cattle feces - growth - mineralization - decomposition - netherlands - deterrents
To assess cattle slurry manure quality in relation to feeding strategy, a field experiment and a bio-assay were carried out with slurries from four dairy farming systems that used diets differing in protein content and digestibility. Several quality aspects were evaluated. In the field experiment the effects of slurry manure type on herbage rejection by grazing heifers and herbage yield on undisturbed plots under cages were studied for a grass monoculture and a grass/clover mixture. The bio-assay, consisting of a cress (Lepidium sativum L.) seed germination test, was used to study differences in phytotoxicity between the slurry types. After five weeks of undisturbed growth at equal amounts of applied inorganic nitrogen (N), the herbage yields differed statistically for the different slurries. This was probably due to immobilization of N in the case of the two slurries from farming systems in which straw was fed and used as bedding material. Herbage rejection by grazing animals was significantly shown for all slurry types and was significantly and positively correlated with the NH3/NH4 +-N content of the slurry. The slurries showed large differences in phytotoxicity to seeds and seedlings in the bio-assay. Ammonia and electric conductivity appeared to be the most important slurry parameters with inhibiting effects. The slurries with a high C/N ratio showed lowest phytotoxicity. Phytotoxicity in the cress seed germination test did not account for reduced herbage yields in the field experiment. On the contrary, when the slurries were ranked according to their phytotoxicity the order was the same as the ranking on the basis of undisturbed herbage yield. It was concluded that there is a need for other laboratory tests that show greater resemblance with what is observed in the field to assess slurry quality.