HEMOLYSIN: A POTENTIAL VIRULENCE FACTOR OF Edwardsiella ictaluri AND THE USE OF RANDOM MUTAGENESIS IN THIS DETERMINATION

摘要

Edwardsiella ictaluri is the causative agent of enteric septicemia of catfish (ESC), an important disease for the channel catfish industry. The pathogenesis of ESC is not fully understood; however, several characteristics have been examined as potential virulence factors. One of these is a cell-associated hemolysin. Hemolysins have been shown to be virulence factors for other bacterial pathogens including Actinobacillus pleuropneumonae, Listeria monocytogenes, Leptospira sp., and Streptococcus pneumonae. A study by Stanley et al.1 determined that there was no clear relationship between hemolytic activity and virulence of E. ictaluri. This assay was performed using bacterial broth cultures incubated with a suspension of 5% sheep red blood cells. Since differences in hemolytic activity could be attributable to differences in growth patterns, we repeated this study using stationary phase bacteria suspended in hemolysin buffer. We found, as Stanley et al. had, that hemolysin activity varied greatly between isolates and that virulent strains appeared to produce more hemolysis than their corresponding attenuated strains.