The mycobactericidal properties of whole blood and plasma in South African species

Abstract

In wildlife species, relatively little is known about interspecific variation of innate immune response to infection with pathogens. In order to optimize methods, a pilot study to test the ability of 20_l of whole blood and 10_l of plasma to inhibit Escherichia coli, Staphylococcus aureus and Bovine BCG was conducted. Following this, the capability of whole blood and plasma from ten species of South African vertebrates to inhibit the growth of Escherichia coli, Staphylococcus aureus and Bovine BCG bacteria was tested at concentrations of 5_l, 10_l, 20_l, 50_l, 100_l and 200_l. Inhibition ability varied significantly between species, with the scavenging species spotted hyena, Nile crocodile and palm nut vulture exhibiting the lowest minimum inhibitory volume of blood and the highest overall inhibition activity. EC50 values for scavenging species was significantly lower than that of herbivorous species. In all species, E. coli and Bovine BCG bacteria were inhibited with a complement mediated response and were inhibited by both whole blood and plasma. S. aureus induced a cell-mediated response and was inhibited by whole blood but not by plasma. The sex and age of an individual, as well as the season in which the samples was collected did not significantly affect the results. We further studied the leukocyte proliferation of ten species of vertebrates in response to E. coli, S. aureus and Bovine BCG bacteria. The results show that scavengers have higher overall numbers of circulating leukocytes than did carnivores and herbivores. After addition of bacterial species to whole blood, statistically significant post-hoc comparisons of leukocyte numbers were found in species known to supplement their diet with carrion.