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Hypochlorite scavenging by Pseudomonas aeruginosa alginate
Infection and Immunity
|August 1, 1987
Summary
Pseudomonas aeruginosa alginate scavenges hypochlorite, a reactive oxygen species. This protects bacteria from immune cells, potentially increasing virulence in infections like cystic fibrosis.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen, particularly problematic in cystic fibrosis patients due to its mucoid strains.
- Mucoid P. aeruginosa produces alginate, an extracellular polysaccharide, but its role in virulence is not fully understood.
- Phagocytes generate hypochlorite (HOCl) as a key microbicidal agent.
Purpose of the Study:
- To investigate the interaction between Pseudomonas aeruginosa alginate and hypochlorite.
- To determine if alginate contributes to bacterial resistance against host defenses.
- To elucidate the mechanism by which alginate might enhance bacterial virulence.
Main Methods:
- Purification of alginic acid from a mucoid P. aeruginosa clinical isolate.
- Assessing the effect of purified alginate on neutrophil chemiluminescence and oxygen consumption.
- Evaluating the hypochlorite-scavenging capacity of purified alginate compared to seaweed alginate and dextran.
- Investigating the role of uronic acid and O-acetyl groups in alginate's scavenging ability.
- Comparing the survival of mucoid and non-mucoid P. aeruginosa strains exposed to hypochlorite.
Main Results:
- Pseudomonas aeruginosa alginate inhibited neutrophil chemiluminescence but not oxygen consumption, indicating interference with hypochlorite.
- Purified P. aeruginosa alginate effectively scavenged hypochlorite, while seaweed alginate was less effective and dextran was ineffective.
- The uronic acid core and O-acetyl groups of P. aeruginosa alginate appear crucial for its hypochlorite-scavenging activity.
- Mucoid P. aeruginosa exhibited greater resistance to hypochlorite killing than a non-mucoid revertant.
- Adding purified alginate to the non-mucoid strain conferred protection against hypochlorite.
Conclusions:
- Pseudomonas aeruginosa alginate possesses significant hypochlorite-scavenging properties.
- This scavenging ability protects the bacteria from the microbicidal effects of phagocyte-generated hypochlorite.
- Alginate may enhance P. aeruginosa virulence by neutralizing host-generated oxidants, contributing to persistent infections, especially in cystic fibrosis.
