Metabolic activity of pathogenic bacteria during semicontinuous anaerobic digestion

In natural environments such as anaerobic digesters, bacteria are frequently subjected to the stress of nutrient fluxes because of the continual changes in the flow of nutrients, and to survive, they must be capable of adapting readily to nutrient changes. In this study, the metabolic activities of Escherichia coli, Salmonella typhimurium, Yersinia enterocolitica, Listeria monocytogenes, and Campylobacter jejuni were studied within culture bags (Versapor -200 filters, 0.22 - microns pore size) in laboratory anaerobic digesters. The metabolic activity of these bacteria was indicated by their adenylate energy charge (EC) ratios and their ability to incorporate [3H] thymidine, which was related to the respective changes in viable number within the culture bags during anaerobic digestion. Fluctuations in the adenylate EC ratios, the uptake of [3H] thymidine, and the viable numbers of E. coli, S. typhimurium, Y enterocolitica, and L. monocytogenes cells were probably due to constant changes in the amount of available nutrients within the anaerobic digesters. The viability of S.typhimurium increased quickly after a fresh supply of nutrients was added to the system as indicated by the uptake of [3H] thymidine and an increase in the adenylate EC ratios. The viable numbers of E. coli, S. typhimurium, Y. enterocolitica, and L. monocytogenes organisms declined rapidly from 10 (7) to 10 (8) CFU/ml to 10(3) to 10 (4) CFU/ml and remained at this level for an indefinite period. The decimal reduction time calculated during the period of exponential decline ranged from 0.8 to 1.2 days for these bacteria. C. jejuni had the greatest mean decimal reduction time value (3 - 6 days).(AU)

Frequency of isolation of Yersinia enterocolitica from livestock in Trinidad

As part of a study to determine the enteric pathogens associated with diarrhoea in livestock in Trinidad, rectal swabs were taken from diarrhoeic and non-diarrhoeic calves, piglets, lambs and kids. Swabs were transported to the laboratory ice-cooled in Amies transport medium within two hours of collection and then enriched in 0.067 M phosphate buffered saline, pH 7.6 for three weeks at 4§C. Subcultures were made on to Yersinia selective medium (Oxoid) after one and three weeks and incubated at room temperature (22 to 25§C) for 24 to 48 hours. Pinkish 'bull-eyed' colonies were picked and subjected to biochemical tests as reported by Shiemann and Flemming (1981). The confirmation of isolates, serotyping and biotyping were kindly done at the Laboratory Centre for Disease Control in Ontario, Canada (AU)