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Modulatory effect of iron on the pathogenesis of Pseudomonas aeruginosa mouse corneal infections
Abstract:
The iron concentration of the culture medium used to prepare the inocula influenced the pathogenesis of mouse corneal infections by Pseudomonas aeruginosa. When the parental strain PAO1 was cultured in high-iron medium (5 micrograms of Fe per ml), it was less virulent than when it was cultured in low-iron medium (0.05 microgram of Fe per ml). The iron concentration of the growth medium had no effect on the virulence of a P. aeruginosa mutant which was resistant to the iron regulation of toxin A yields (PAO-toxFeR-18). A severely defective iron transport mutant, PAO-toxFeR-10, was avirulent regardless of the iron concentration of the growth medium. These studies indicate that both iron acquisition and iron regulation of toxin production are important factors in the determination of P. aeruginosa virulence.
Insights
Iron levels in growth media impact Pseudomonas aeruginosa virulence. Lower iron concentrations increase pathogenicity, while iron acquisition and toxin regulation are key to P. aeruginosa virulence.
Area of Science:
- Microbiology
- Infectious Diseases
- Ophthalmology
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen that causes severe corneal infections.
- Iron is a critical nutrient for bacterial growth and virulence factor production.
- Iron acquisition and regulation mechanisms are essential for P. aeruginosa pathogenesis.
Purpose of the Study:
- To investigate the role of iron concentration in the culture medium on the virulence of Pseudomonas aeruginosa in a mouse corneal infection model.
- To determine the impact of iron availability on the expression of virulence factors, specifically toxin A.
- To elucidate the interplay between iron uptake, toxin regulation, and bacterial pathogenicity.
Main Methods:
- Preparation of Pseudomonas aeruginosa inocula in culture media with varying iron concentrations (high: 5 µg/ml, low: 0.05 µg/ml).
- Infection of mouse corneas with the parental strain (PAO1) and specific mutants (PAO-toxFeR-18, PAO-toxFeR-10).
- Assessment of bacterial virulence and pathogenicity following corneal inoculation.
Main Results:
- The parental strain PAO1 exhibited reduced virulence when cultured in high-iron medium compared to low-iron medium.
- Iron concentration did not affect the virulence of a mutant resistant to iron regulation of toxin A (PAO-toxFeR-18).
- A severe iron transport mutant (PAO-toxFeR-10) was avirulent irrespective of the growth medium's iron concentration.
Conclusions:
- Iron acquisition mechanisms are crucial for Pseudomonas aeruginosa virulence in corneal infections.
- Iron regulation of toxin production plays a significant role in P. aeruginosa pathogenicity.
- Both efficient iron uptake and regulated toxin expression are vital determinants of P. aeruginosa virulence.