Role of rpoS in Acid Resistance and Fecal Shedding of Escherichia coli O157:H7
Autor: | John W. Foster, James C. Wright, Charles W. Kaspar, Fred J. DeGraves, Chorng-Ming Cheng, Stuart Price, Marie-Pierre Castanie-Cornet, Thomas Penfound |
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Rok vydání: | 2000 |
Předmět: |
Arginine
Mutant Colony Count Microbial Sigma Factor Biology Escherichia coli O157 medicine.disease_cause Applied Microbiology and Biotechnology Microbiology Feces Mice Bacterial Proteins medicine Environmental Microbiology and Biodegradation Animals Humans Escherichia coli Pathogen Escherichia coli Infections Mice Inbred ICR Ecology Strain (chemistry) Hydrogen-Ion Concentration biology.organism_classification Enterobacteriaceae Mutation Cattle rpoS Bacteria Food Science Biotechnology |
Zdroj: | Applied and Environmental Microbiology. 66:632-637 |
ISSN: | 1098-5336 0099-2240 |
Popis: | Acid resistance (AR) is important to survival of Escherichia coli O157:H7 in acidic foods and may play a role during passage through the bovine host. In this study, we examined the role in AR of the rpoS -encoded global stress response regulator ς S and its effect on shedding of E. coli O157:H7 in mice and calves. When assayed for each of the three AR systems identified in E. coli , an rpoS mutant ( rpoS ::pRR10) of E. coli O157:H7 lacked the glucose-repressed system and possessed reduced levels of both the arginine- and glutamate-dependent AR systems. After administration of the rpoS mutant and the wild-type strain (ATCC 43895) to ICR mice at doses ranging from 10 1 to 10 4 CFU, we found the wild-type strain in feces of mice given lower doses (10 2 versus 10 3 CFU) and at a greater frequency (80% versus 13%) than the mutant strain. The reduction in passage of the rpoS mutant was due to decreased AR, as administration of the mutant in 0.05 M phosphate buffer facilitated passage and increased the frequency of recovery in feces from 27 to 67% at a dose of 10 4 CFU. Enumeration of E. coli O157:H7 in feces from calves inoculated with an equal mixture of the wild-type strain and the rpoS mutant demonstrated shedding of the mutant to be 10- to 100-fold lower than wild-type numbers. This difference in shedding between the wild-type strain and the rpoS mutant was statistically significant ( P ≤ 0.05). Thus, ς S appears to play a role in E. coli O157:H7 passage in mice and shedding from calves, possibly by inducing expression of the glucose-repressed RpoS-dependent AR determinant and thus increasing resistance to gastrointestinal stress. These findings may provide clues for future efforts aimed at reducing or eliminating this pathogen from cattle herds. |
Databáze: | OpenAIRE |
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