ABSTRACT
AIM: To investigate the survival of Escherichia coli O157:H7 and Salmonella Typhimurium in cowpats on pasture in a temperate Nordic climate. METHODS AND RESULTS: The study consists of two parts, the first part using artificially created cowpats inoculated with E. coli O157:H7 and S. Typhimurium and the second part using cowpats from empty pastures on which cattle herds positive for E. coli O157:H7 had grazed 6 month previously. Artificial cowpats were created, placed in an outdoor field station in June, August and October, and sampled over 1 year. Escherichia coli O157:H7 and S. Typhimurium were analysed by standard culture methods. The results showed viable E. coli O157:H7 and S. Typhimurium in the sampled cowpats throughout the 365-day sample period for the June trial, 250 days for the August trial and 40-70 days for the October trial. In addition, 200 natural cowpats were sampled from eight pastures that had previously held E. coli O157:H7 positive cattle herds. Five positive E. coli O157:H7 isolates were obtained, all with the same multi-locus variable number tandem repeat analysis pattern as had been found on the pasture the previous grazing season. CONCLUSIONS: Escherichia coli O157:H7 and S. Typhimurium can survive in cowpats up to a year and persist throughout a winter season. Therefore, there is a possibility that cowpats can act as a reservoir and be a source of re-infection of Salmonella or E. coli O157:H7 in cattle between grazing seasons. SIGNIFICANCE AND IMPACT OF THE STUDY: The obtained results can provide valuable information for managing the risk posed by zoonotic pathogens originating from farm environments.
Subject(s)
Escherichia coli O157/physiology , Salmonella typhimurium/physiology , Animals , Cattle , Escherichia coli O157/genetics , Escherichia coli O157/isolation & purification , Manure/microbiology , Microbial Viability , Minisatellite Repeats , Salmonella typhimurium/isolation & purificationABSTRACT
Transcription was determined in liver chromatin from rats fed for 6 days, an optimal (20%) or suboptimal (3%) amount of high-quality protein. Transcription by Escherichia coli RNA polymerase (EC 2.7.7.6) was lower after prolonged incubation with chromatin from rats fed 3% as compared with 20% protein. Differences were detected in the transcripts of the two types of chromatin after analysis by sucrose density gradient centrifugation. But no measurable differences were found in the melting profiles at low ionic strength of the two chromatin preparations. Transcription per milligram chromatin DNA was 25-fold higher using E. coli RNA polymerase instead of rat liver RNA polymerase II. The use of UTP as radioactive precursor in the absence of ATP, GTP and CTP resulted in a low labelling of RNA. One [lambda32P]UTP nucleotide was incorporated/8 UMP nucleotides. The product obtained was sensitive to ribonuclease treatment. In the presence of ATP, GTP and CTP [lambda-32P]UTP nucleotide incorporation was reduced and that of UMP nucleotide was increased giving a ratio of 1:188.
Subject(s)
Chromatin , DNA-Directed RNA Polymerases , Dietary Proteins , Liver/ultrastructure , Templates, Genetic , Transcription, Genetic , Animals , Centrifugation, Density Gradient , Dietary Proteins/administration & dosage , Escherichia coli , Liver/enzymology , Male , RNA/biosynthesis , RatsSubject(s)
Chromatin/metabolism , DNA-Directed RNA Polymerases/metabolism , Liver/metabolism , Protein Deficiency/metabolism , RNA Polymerase II/metabolism , RNA Polymerase I/metabolism , Transcription, Genetic , Animals , Dietary Proteins , Kinetics , Male , RNA/biosynthesis , Rats , Templates, GeneticABSTRACT
Rats were fed for 6 days on a diet containing either 3 or 20% high-quality protein. Nuclei were isolated from liver and DNA-dependent RNA polymerases (EC 2.7.7.6) extracted with 1 M-(NH4)2SO4. The proteins were then precipitated with 3.5 M-(NH4)2SO4 and after dialysis applied to a DEAE-Sephadex column. The column was developed with a gradient of (NH4)2SO4. Polymerase I separated well from alpha-amanitin-sensitive polymerase II. The enzyme activities were compared between the two dietary groups. Rats that had received 3% protein showed a lower polymerase I activity per g wet wt. of liver, per mg of DNA and per mg of protein. Polymerase II was lower in activity per g wet wt. of liver and per mg of DNA, but was higher per mg of protein. Polyacrylamide-gel electrophoretograms showed a higher proportion of contaminating proteins in polymerase II fractions isolated from 20%-protein-fed rats. The data explain the lower activity obtained per mg of protein in these rats. It is concluded that a decrease in dietary protein content from 20 to 3% induces a fall in content and specific activity of RNA polymerase I and II in liver.
