Survival of Escherichia coli O157:H7 in soils under different land use types

Abstract

Laboratory studies on Escherichia coli O157:H7 survival in soils from four different land use types: forest, tea plantation, bamboo grove, and vegetable garden were investigated at 25 ± 1 °C with the field capacity (soil water content at -33 kPa). Results showed that E. coli O157:H7 declined quickly in the test soils, but its survival dynamics varied in the soils under different land use types. The survival time needed to reach the detection limit (t d) in the test soils ranged from 2.1 to 3.6 days, with slightly longer t d values being observed in soils from the bamboo grove. Stepwise multiple regression analysis revealed that the t d values were shorter in sandy, lower pH, and lower organic carbon content soils. Different E. coli O157:H7 survival time in the soils under different land uses suggests that it is important to adapt proper management practices for reducing the potential risks of pathogen contamination when diary manure is applied to agricultural land.

Interaction between the Microbial Community and Invading Escherichia coli O157:H7 in Soils from Vegetable Fields

“…Before the inoculation experiment, the soil samples, previously stored at 4°C, were incubated in a darkroom at 25 Ϯ 1°C for 5 days to activate the soil microbial communities (9,32). E. coli O157:H7 derived from E. coli O157:H7 EDL933 (ATCC 43895) was used as the test bacterial strain, as described previously by Yao et al (9).…”

“…At 0, 0.04, 1, 3, 5, 7, 10, 15, and 25 days after inoculation, approximately 0.5 g (oven-dry weight) of soil sample was taken from each tube to determine the survival of E. coli O157:H7 over time (9). The experimental data were fitted to the Weibull survival function by the following equation, as described by Wang et al (32):…”

“…p , where N t represents the number of surviving cells remaining at time t, N 0 is the inoculum size, p is the shape parameter, and ␦ is the scale parameter that represents the time (day) needed for first decimal reduction (32)(33)(34). The time when N t reaches the detection limit (100 CFU · g Ϫ1 ), t d , can also be calculated from this equation.…”

Enteropathogen survival in soil from different land-uses is predominantly regulated by microbial community composition

“…PLFA loadings show that the suppressive effect observed in this case was of a general community-scale basis rather than specialist nature, caused by interactions with the total microbial consortium within these soils, rather than with specific microbial groups, which would be indicated by a few dominant PLFAs in the loadings. This suggests that the pathogen risk is higher when applying organic materials to arable soils relative to grasslands, as these soils may lack suppressive capacity associated with higher microbial diversity that tends to be promoted by intermediate A recent study by Wang et al (2014) showed that landuse factors including soil pH, organic matter and sand content significantly influenced the decay of E. coli O157; however the authors did not take account of the inherent soil biology associated with each land-use type. In contrast, we observed that none of the physico-chemical factors included in this study could explain differences in pathogen survival between soils, when PC scores representing the community context were included in regression analysis (Table 4).…”

Microbes in the Anthropocene: spillover of agriculturally selected bacteria and their impact on natural ecosystems

“…There is a rapid decline of antibiotic resistance genes with distance from the treatment plants, indicating a cost to carriage of the genes that is difficult to detect under laboratory conditions, resulting in negative population growth rates in low-antibiotic environments. Similarly, there are rapid rates of decline of well-studied obligate pathogens when dispersing into natural environments [75]. While decline rates are rapid, they are by no means instantaneous even for bacteria for which soil must be extremely harsh relative to their typical environment.…”