Characterization of hemolysin in extracellular products of Pseudomonas cepacia

Abstract

Pseudomonas cepacia is recognized as an opportunistic pathogen in immunocompromised patients. We screened 120 strains of P. cepacia isolated from clinical specimens for production of extracellular products. About 70% of these strains produced lipase, protease, and lecithinase, but only 4% produced hemolysin. A hemolysin produced by P. cepacia JN106 was characterized. The hemolysin was most active against human erythrocytes. Horse, sheep, chicken, and rabbit erythrocytes were also susceptible. The hemolysin was heat labile and was inhibited by sterols but was not activated by 2-mercaptoethanol and dithiothreitol. Four hemolysin-negative mutants obtained by N-methyl-N'-nitro-N-nitrosoguanidine treatment produced the other extracellular products. A 58-kilobase-pair plasmid found in the parent strain was also found in the mutant strains, suggesting that the hemolysin gene resides on the chromosome.