ABSTRACT
BACKGROUND & OBJECTIVES: Serratia marcescens an opportunistic human pathogen, is frequently encountered in a variety of debilitating diseases. Relatively little is known about its virulence traits though most clinical isolates secrete a distinct haemolysin which is considered as a useful marker for pathogenicity of Serratia. In this study purification and characterisation of S. marcescens B-91 haemolysin have been attempted. METHODS: S. marcescens B-91 haemolysin was purified to homogeneity from the growth medium using ammonium sulphate fractional precipitation and gel filtration through Sephadex G-75 column. Homogeneity was determined by gel electrophoresis and purified haemolysin was tested for its stability and other characteristics. RESULTS: The haemolysin was characterised to be a 45 kDa molecular weight protein on SDS-polyacrylamide gel electrophoresis. It was inactivated at 60-100 degrees C within 30 min, and on overnight treatment with 2 per cent formaldehyde. It was also susceptible to the action of pronase, protease and trypsin. INTERPRETATION & CONCLUSIONS: The results indicate that the fragile stability of S. marcescens haemolysin is dependent on the storage temperature. The purified haemolysin can be used for understanding the role of haemolysin in the pathogenesis of S. marcescens and also for evaluation of immunoprophylactic activity.