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Virulence Attributes and Host Response Assays for Determining Pathogenic Potential of Pseudomonas Strains Used in
Azam F Tayabali1, Gordon Coleman1, Kathy C Nguyen1
1Biotechnology Laboratory, Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Environmental Health Centre, Health Canada, Ottawa, Ontario, Canada.
Abstract:
Pseudomonas species are opportunistically pathogenic to humans, yet closely related species are used in biotechnology applications. In order to screen for the pathogenic potential of strains considered for biotechnology applications, several Pseudomonas strains (P.aeruginosa (Pa), P.fluorescens (Pf), P.putida (Pp), P.stutzeri (Ps)) were compared using functional virulence and toxicity assays. Most Pa strains and Ps grew at temperatures between 28°C and 42°C. However, Pf and Pp strains were the most antibiotic resistant, with ciprofloxacin and colistin being the most effective of those tested. No strain was haemolytic on sheep blood agar. Almost all Pa, but not other test strains, produced a pyocyanin-like chromophore, and caused cytotoxicity towards cultured human HT29 cells. Murine endotracheal exposures indicated that the laboratory reference strain, PAO1, was most persistent in the lungs. Only Pa strains induced pro-inflammatory and inflammatory responses, as measured by elevated cytokines and pulmonary Gr-1 -positive cells. Serum amyloid A was elevated at ≥ 48 h post-exposure by only some Pa strains. No relationship was observed between strains and levels of peripheral leukocytes. The species designation or isolation source may not accurately reflect pathogenic potential, since the clinical strain Pa10752 was relatively nonvirulent, but the industrial strain Pa31480 showed comparable virulence to PAO1. Functional assays involving microbial growth, cytotoxicity and murine immunological responses may be most useful for identifying problematic Pseudomonas strains being considered for biotechnology applications.
Insights
Assessing Pseudomonas strains for biotechnology use is crucial. Functional assays measuring virulence and toxicity can identify potentially pathogenic strains, as species alone may not reflect risk.
Area of Science:
- Microbiology
- Pathogen identification
- Biotechnology safety
Background:
- Pseudomonas species present a dual role: opportunistic human pathogens and valuable biotechnology tools.
- Distinguishing pathogenic potential among Pseudomonas strains is essential for safe biotechnological applications.
Purpose of the Study:
- To compare the virulence and toxicity of different Pseudomonas species (P. aeruginosa, P. fluorescens, P. putida, P. stutzeri).
- To evaluate the utility of functional assays in screening Pseudomonas strains for pathogenic potential before biotechnological use.
Main Methods:
- Functional virulence and toxicity assays were performed on selected Pseudomonas strains.
- Assays included microbial growth, antibiotic resistance, haemolytic activity, chromophore production, cytotoxicity, and murine immunological responses (cytokines, Gr-1+ cells, Serum amyloid A).
Main Results:
- P. aeruginosa and P. stutzeri showed broad temperature growth, while P. fluorescens and P. putida exhibited higher antibiotic resistance.
- Only P. aeruginosa strains produced a pyocyanin-like chromophore, induced cytotoxicity in HT29 cells, and triggered significant pro-inflammatory and inflammatory responses in murine models.
- Strain virulence varied independently of species or source, with an industrial P. aeruginosa strain exhibiting high virulence.
Conclusions:
- Functional assays are more reliable than species designation or isolation source for assessing pathogenic potential in Pseudomonas.
- These assays are vital for identifying strains that pose a risk for biotechnology applications.
- P. aeruginosa strains demonstrated greater pathogenic characteristics compared to other tested species.
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