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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.
Insights
Pseudomonas cepacia, an opportunistic pathogen, was studied for extracellular products. Most strains produced lipase, protease, and lecithinase, but hemolysin production was rare, suggesting its gene is chromosomal.
Area of Science:
- Microbiology
- Bacteriology
- Pathogen Research
Background:
- Pseudomonas cepacia is an opportunistic pathogen, particularly affecting immunocompromised individuals.
- Understanding the virulence factors of P. cepacia is crucial for managing infections.
Purpose of the Study:
- To screen clinical isolates of Pseudomonas cepacia for extracellular product formation.
- To characterize the hemolysin produced by P. cepacia.
Main Methods:
- Screening of 120 clinical P. cepacia isolates for lipase, protease, lecithinase, and hemolysin production.
- Biochemical characterization of the P. cepacia hemolysin.
- Generation and analysis of hemolysin-negative mutants using N-methyl-N'-nitro-N-nitrosoguanidine.
Main Results:
- Approximately 70% of strains produced lipase, protease, and lecithinase; only 4% produced hemolysin.
- The P. cepacia hemolysin exhibited broad erythrocyte activity, was heat labile, and inhibited by sterols.
- Hemolysin-negative mutants retained other extracellular enzyme production, and a 58-kb plasmid was present in both parent and mutant strains.
Conclusions:
- Hemolysin production is uncommon in the screened P. cepacia isolates.
- The hemolysin gene in P. cepacia JN106 is likely located on the chromosome, not on the identified plasmid.