Prevalence of Shiga Toxin-Producing Escherichia coli stx ₁ , stx ₂ , eaeA , and rfbE Genes and Survival of E. coli O157:H7 in Manure from Organic and Low-Input Conventional Dairy Farms

Abstract

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.Shiga-toxin producing Escherichia coli (STEC) is an important group of zoonotic human pathogens, with E. coli O157 being the best known and most studied serotype (10). STEC strains are generally carried asymptomatically by cattle and shed in their feces, which in turn may serve as a means of maintenance and spread of these pathogens among cattle herds (47). Since the reported increase in food-borne disease associated with the consumption of fresh vegetables (51, 54), the potential contamination of vegetable crops that are grown in fields enriched with manure has raised increasing concern (18, 29, 52). Understanding on-farm survival and spread of human pathogens is of utmost importance in preventing the spread of this organism to the environment, groundwater, food, and crops and subsequently back to cattle.A considerable body of literature exists on the prevalence of STEC on cattle farms and statistically associated management factors which could be used for potential intervention strategies to reduce shedding of these pathogens (2, 53, 57). However, these studies are not unambiguous and have resulted in the identification of only a very few risk factors, like season and cattle age, which are ubiquitous. The direction of influence of the majority of the management practices like feeding regimen and housing conditions remains unclear and is under debate.D...

Shiga-toxigenic Escherichia coli in ready-to-eat food staffs: Prevalence and distribution of putative virulence factors

“…They represented that 54.54% of E. coli isolates were STEC. In addition to our results and also finding of Momtaz et al, 13 Hemmatinezhad et al 14 and Ranjbar et al, 15 simultaneous presences of stx1, stx2, eaeA and ehly virulence factors have also been reported by Franz et al, 17 JayRussell et al 18 and Kabiru et al 19 …”

Escherichia coli Contamination of Lettuce Grown in Soils Amended with Animal Slurry

“…According to the National Organic Program regulations, ''proper'' composting implies that the stored manure reach a temperature above 55uC for several continuous days, depending on the level of aeration (stacked manure must be turned). The length of time needed to reach a satisfactory reduction of pathogens after fertilization depends also on the initial concentration in the manure (12), which again partly depends on the source, age, and storage conditions of the manure (19,26,39). Storage of manure with no continuous input will decrease pathogen numbers, but the rate of decline varies due to the composition of the manure, temperature, and other physicochemical factors (5).…”

“…Animal manure is a potential source of zoonotic pathogens such as Salmonella, Campylobacter, verotoxinproducing E. coli, and protozoan parasites, because many animals shed these pathogens asymptomatically in their feces (2,19,27). Pathogens persist in manure for a variable length of time, depending on the storage conditions, e.g., in stacked heaps or slurry tanks, which affect heat development, a main determinant of pathogen survival (5,20,22,26,39).…”

Microbial diversity determines the invasion of soil by a bacterial pathogen

“…In this context, the microbial communities that established after soil fumigation were shown to determine the fate of the invading species, whereby reduction in microbial diversity due to progressively enhanced fumigation depths resulted in higher pathogen persistence in soil (21). Similarly, in 25 different manures, the decline rate of E. coli O157:H7 was negatively correlated with Enterobacteriaceae richness (22). Furthermore, the easily available carbon content of the manure explained this decline rate (22).…”

“…Similarly, in 25 different manures, the decline rate of E. coli O157:H7 was negatively correlated with Enterobacteriaceae richness (22). Furthermore, the easily available carbon content of the manure explained this decline rate (22). A study in organic manure-amended soil showed a faster pathogen decline when rates of nutrient flow were reduced (23).…”