Analysis of the variability in the number of viable bacteria after mild heat treatment of food.

Variability in the numbers of bacteria remaining in saline solution and whole milk following mild heat treatment has been studied with Listeria innocua, Enterococcus faecalis, Salmonella enterica serovar Enteritidis, and Pseudomonas fluorescens. As expected, the most heat-resistant bacterium was E. faecalis, while P. fluorescens was the least heat resistant, and all bacteria showed greater thermal resistance in whole milk than in saline solution. Despite the differences in the inactivation kinetics of these bacteria in different media, the variability in the final number of bacteria was affected neither by the species nor by the heating substrate, but it did depend on the intensity of the heat treatment. The more severe the heat treatment was, the lower the average number of surviving bacteria but the greater the variability. Our results indicated that the inactivation times for the cells within a population are not identically distributed random variables and that, therefore, the population includes subpopulations of cells with different distributions for the heat resistance parameters. A linear relationship between the variability of the log of the final bacterial concentration and the logarithmic reduction in the size of the bacterial population was found.

Nocturnal oxygen therapy in patients with the Eisenmenger syndrome.

This prospective and controlled pilot study evaluates the long-term effects of nocturnal oxygen therapy (NOT) on exercise endurance, hematology variables, quality of life, and survival of 23 adult patients (mean age, 32 +/- 6 yr) with post-tricuspid congenital heart defects (ventricular septal defect = 10; patent ductus arteriosus = 13) and Eisenmenger Syndrome. All had pulmonary hypertension (mean pulmonary artery pressure = 88 +/- 20 mm Hg), severe hypoxemia (Pa(O(2)) = 44 +/- 5 mm Hg), and secondary erythrocytosis (hematocrit = 61.5 +/- 7%). Exercise endurance (6-min walk test = 380 +/- 88 m) was limited. In a random fashion, NOT was given to one group of patients (n = 12) but withheld from a comparable control group (n = 11). At 2 yr of close follow-up, two patients in the group of control patients, and three in the treatment group died. Mean survival estimates were similar in both groups (20.7 versus 20.8 mo; chi-square log-rank, 0.08; p = NS). Likewise, none of the hematology, exercise capacity, and quality of life variables examined showed statistically significant changes that were dependent on treatment regimen. We conclude that NOT does not modify the natural history of patients with advanced Eisenmenger Syndrome.