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)

Antimicrobial resistance in organisms isolated at the University Hospital of the West Indies during 1975

The results of standardized disc-sensitivity testing for common bacterial pathogens isolated from clinical specimens at the University Hospital of the West Indies during 1975 are reported. Antibiotic resistance and multiple resistance is now common, multiple resistance occurring in 54 percent of Gram negative isolates and 37 percent of Gram positives. Seventy-nine per cent isolates of Staphylococcus aureus were resistant to penicillin but only 7 percent were resistant to methicilin. Sixty-three per cent of both Gram negative and Gram positive isolates showed resistance to ampicillin but most organisms remained sensitive to cotrimoxazole. Although S. typhi remained fully sensitive to the commonly-used antibiotics, other Salmonellae showed resistance to both ampicillin and chloraphenicol in 52 percent of isolates. Isolates of Shigellae, however, showed surprisingly little antibiotic resistance. Cotrimoxazole remains an effective agent against most of the multiple-resistant organisms except Pseudomonas aeruginosa. It is suggested that the restriction of the use of chloramphenicol might preserve its effectiveness for serious infections, such as typhoid fever (AU)

Physiological mechanism and pathogenesis of weanling diarrhea

Quantitative aerobic and anaerobic bacteriological studies of the upper and lower jejunum were performed in six malnourished children without diarrhea and in a group of five malnourished children with weanling diarrhea. A third group of children was tested after prolonged treatment in the hospital. All three groups of children had small numbers of mixed aerobic and anaerobic bacteria in the upper and lower intestine; only four children had a total bacterial count above 10[4]/g, and there was no correlation between the numbers or type of organinsms and the nutritional state of the child. Jejunal perfusion studies showed that the children with weanling diarrhea had a marked jejunal accumulation of fluid, i.e., net secretion, similar to that seen in cholera. Malnourished or treated children without diarrhea did not show this abnormality. Glucose promoted water absorption even in children with gastroenteritis who had reduced glucose absorption rates. No enterotoxin-producing organisms were isolated to account for these functional changes. Treating cases of weanling diarrhea with low concentrations of oral glucose should promote positive water and electrolyte balance, but this effect will be limited by the degree of glucose malabsorption in the individual child. (Summary)