The blood clearance of 51 Cr-labelled heat-killed Salmonella pullorum at 8°C was biphasic and exponential for each phase. This pattern was the same for all three concentrations of bacteria used. The initial more rapid phase lasted for approximately 15 minutes when roughly 90% of the bacteria had been cleared. The second slower phase started 25 to 30 minutes post-inoculation and lasted for approximately 25 to 30 minutes. The tissue distribution of bacteria showed that in both absolute and relative terms, the kidney was the most important organ, accounting for more than 70% uptake of the bacteria. Starvation had little significant effect on the biphasic pattern.Raising the water temperature from 8°C to 18°C enhanced the rate of clearance of the second phase to almost exactly double that at 8°C. At 18 hours post-inoculation the spleen contained much more radioactivity per gram than any other tissue. This finding is in marked contrast to 8°C at which temperature the kidney contained most, and it suggests that redistribution of bacteria occurred. Temperature stress had little significant effect on tissue localization of bacteria with the exception of the heart: a rising temperature stress caused increased numbers of bacteria to localize within the heart.

These kinetics demonstrate that rainbow trout at 8°C are able to clear their bloodstream of Salmonella very efficiently, in a fashion very similar to mammals. It is not known, however, which of the various possible clearance mechanisms dominates each phase. We have been unable to demonstrate that the vascular clearance mechanisms, including the reticuloendothelial system, are significantly compromised by starvation or by raising the water temperature.