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Published on: June 5, 2012
Sensitivity of Pseudomonas aeruginosa to normal serum and to polymyxin
Abstract:
Strains of Pseudomonas aeruginosa isolated from clinical material were very variable in their sensitivity to the bactericidal action of normal serum mediated by the complement system. Fifty per cent killing end points ranged from 0.015 ml to greater than 0.4 ml. Most of the strains with relatively greater sensitivity to serum were isolated from patients with cystic fibrosis. Immunization of rabbits resulted in antisera with enhanced levels of bactericidal antibody, except with one strain which was resistant to the bactericidal action of normal serum and antiserum. When P. aeruginosa was cultivated at 41 C instead of at 37 C, it was significantly more sensitive to serum and to several antibiotics, thereby implicating fever as a host defense mechanism in Pseudomonas infections. In contrast to their heterogeneity to serum bactericidal activity, the strains were relatively homogeneous in their sensitivity to polymyxin, with no apparent association between their sensitivity to the two antimicrobial agents.
Insights
Pseudomonas aeruginosa strains show varied sensitivity to serum, but fever may enhance host defenses. This study highlights potential therapeutic targets for Pseudomonas infections.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Pseudomonas aeruginosa is a significant opportunistic pathogen.
- Its susceptibility to host immune mechanisms, like complement-mediated serum killing, varies.
- Understanding these variations is crucial for treating infections, especially in vulnerable populations.
Purpose of the Study:
- To investigate the variability in serum sensitivity among clinical isolates of Pseudomonas aeruginosa.
- To explore the role of host factors, such as fever, in modulating Pseudomonas aeruginosa susceptibility.
- To compare serum sensitivity with antibiotic sensitivity, specifically to polymyxin.
Main Methods:
- Assessing serum bactericidal activity against clinical Pseudomonas aeruginosa isolates.
- Evaluating the effect of cultivation temperature (37°C vs. 41°C) on bacterial sensitivity.
- Testing sensitivity to polymyxin.
Main Results:
- Significant variability in 50% killing endpoints of serum bactericidal activity was observed.
- Isolates from cystic fibrosis patients were generally more serum-sensitive.
- Cultivation at 41°C significantly increased sensitivity to serum and antibiotics.
- Strains showed homogeneous sensitivity to polymyxin, unrelated to serum sensitivity.
Conclusions:
- Pseudomonas aeruginosa exhibits heterogeneous sensitivity to serum, influenced by patient factors and potentially temperature.
- Fever, by increasing bacterial sensitivity, may act as a host defense mechanism.
- Polymyxin sensitivity is independent of serum sensitivity, suggesting different therapeutic approaches.
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