Modulatory effect of iron on the pathogenesis of Pseudomonas aeruginosa mouse corneal infections.

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.