General suppression of Escherichia coli O157:H7 in sand-based dairy livestock bedding.
ABSTRACT Sand bedding material is frequently used in dairy operations to reduce the occurrence of mastitis and enhance cow comfort. One objective of this work was to determine if sand-based bedding also supported the microbiologically based suppression of an introduced bacterial pathogen. Bedding samples were collected in summer, fall, and winter from various locations within a dairy operation and tested for their ability to suppress introduced populations of Escherichia coli O157:H7. All sources of bedding displayed a heat-sensitive suppressiveness to the pathogen. Differences in suppressiveness were also noted between different samples at room temperature. At just 1 day postinoculation (dpi), the recycled sand bedding catalyzed up to a 1,000-fold reduction in E. coli counts, typically 10-fold greater than the reduction achieved with other substrates, depending on the sampling date. All bedding substrates were able to reduce E. coli populations by over 10,000-fold within 7 to 15 dpi, regardless of sampling date. Terminal restriction fragment length polymorphism (T-RFLP) analysis was used to identify bacterial populations potentially associated with the noted suppression of E. coli O157:H7 in sand bedding. Eleven terminal restriction fragments (TRFs) were overrepresented in paired comparisons of suppressive and nonsuppressive specimens at multiple sampling points, indicating that they may represent environmentally stable populations of pathogen-suppressing bacteria. Cloning and sequencing of these TRFs indicated that they represent a diverse subset of bacteria, belonging to the Cytophaga-Flexibacter-Bacteroidetes, Gammaproteobacteria, and Firmicutes, only a few of which have previously been identified in livestock manure. Such data indicate that microbial suppression may be harnessed to develop new options for mitigating the risk and dispersal of zoonotic bacterial pathogens on dairy farms.
Full-textDOI: · Available from: Michele L Williams, May 28, 2015
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ABSTRACT: Escherichia coli O157:H7 (E. coli O157:H7) is recognized as a hazardous microorganism in the environment and for public health. The E. coli O157:H7 survival dynamics were investigated in 12 representative soils from Jiangsu Province, where the largest E. coli O157:H7 infection in China occurred. It was observed that E. coli O157:H7 declined rapidly in acidic soils (pH, 4.57 - 5.14) but slowly in neutral soils (pH, 6.51 - 7.39). The survival dynamics were well described by the Weibull model, with the calculated td value (survival time of the culturable E. coli O157:H7 needed to reach the detection limit of 100 CFU g(-1)) from 4.57 days in an acidic soil (pH, 4.57) to 34.34 days in a neutral soil (pH, 6.77). Stepwise multiple regression analysis indicated that soil pH and soil organic carbon favored E. coli O157:H7 survival, while a high initial ratio of Gram-negative bacteria phospholipid fatty acids (PLFAs) to Gram-positive bacteria PLFAs, and high content of exchangeable potassium inhibited E. coli O157:H7 survival. Principal component analysis clearly showed that the survival profiles in soils with high pH were different from those with low pH.PLoS ONE 12/2013; 8(12):e81178. DOI:10.1371/journal.pone.0081178 · 3.53 Impact Factor
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ABSTRACT: The Escherichia coli O157:H7 (E. coli O157:H7) survival in soils would contaminate vegetables, fruits or drinking water, etc. However, data on the impact of E. coli O157:H7 on soil microbial communities is limited. In this study, we monitored the changes of indigenous microbial community using phospholipid fatty acids (PLFAs) method to investigate the interaction of soil microbial community with E. coli O157:H7 in soils. Simple correlation analysis showed that E. coli O157:H7 survival in the test soils was negatively correlated with the ratio of Gram-negative (G(-)) bacteria PLFAs to Gram-positive (G(+)) bacteria PLFAs (G(-)/G(+)). In particular, 14 PLFAs were negatively correlated with E. coli O157:H7 survival time. The content of actinomycetes PLFAs and fungi PLFAs in the test soils significantly declined (P < 0.05) after 25 days of incubation with E. coli O157:H7. The G(-)/G(+) ratio declined slightly, while the ratio of bacteria PLFAs to fungi PLFAs (B/F) and the ratio of normal saturated PLFAs to monounsaturated PLFAs (S/M) increased after E. coli O157:H7 inoculation. Principal component analysis results further indicated that the invasion of E. coli O157:H7 had some effects on the soil microbial community. Our data revealed that the toxicity of E. coli O157:H7 presents not only in its pathogenicity but also in its effect on soil micro-ecological environment. Hence, closer attention should be paid to E. coli O157:H7 survival and its potential environmental contamination risk in the soils.Applied and Environmental Microbiology 10/2013; DOI:10.1128/AEM.03046-13 · 3.95 Impact Factor
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ABSTRACT: Escherichia coli O157:H7 (E. coli O157:H7) is an important food-borne pathogen, which continues to be a major public health concern worldwide. It is known that E. coli O157:H7 survive in soil environment might result in the contamination of fresh produce or water source. To investigate how the soils and their properties affect E. coli O157:H7 survival, we studied E. coli O157:H7 survival dynamics in 14 soils collected in eastern China from the warm-temperate zone to subtropical zone. Results showed that E. coli O157:H7 survival as a function of time can be well described by the Weibull model. The calculated td values (survival time to reach the detection limit, 100 colony forming units per gram oven-dried weight of soil) for the test soils were between 1.4 and 25.8 days. A significantly longer survival time (td) was observed in neutral or alkaline soils from north-eastern China (the warm-temperate zone) than that in acidic soils from south-eastern China (the subtropical zone). Distinct E. coli O157:H7 survival dynamics was related to soil properties. Stepwise multiple regression analysis revealed that the td values were significantly enhanced by soil microbial biomass carbon and total nitrogen, but were significantly reduced by amorphous Al2O3 and relative abundance of Chloroflexi. It should pay more attention to E. coli O157:H7 long survival in soils and its potential environmental contamination risk.Science of The Total Environment 04/2014; 476-477:49-56. DOI:10.1016/j.scitotenv.2014.01.004 · 3.16 Impact Factor