1887

Abstract

The gene is the last cistron in the operon and functions as a negative regulator of the Pho regulon. The authors previously identified a mutant of extraintestinal pathogenic strain CFT073 and demonstrated that this mutant was attenuated for survival in the murine model of ascending urinary tract infection. It is hypothesized that the PhoU protein might serve as a urovirulence factor by indirectly affecting the expression of virulence-related genes. In this study, the mutant was further characterized and PhoU was confirmed as a virulence factor. Western blot analysis demonstrated that insertion of the transposon in the gene disrupted the expression of PhoU. The mutant had derepressed alkaline phosphatase activity under phosphate-excess and -limiting conditions. In single-challenge murine ascending urinary tract infection experiments, quantitative cultures of urine, bladder and kidney revealed no significant differences between the mutant strain and the wild-type strain CFT073. However, in competitive colonization experiments, the mutant strain was significantly out-competed by the wild-type strain in the kidneys and urine and recovered in lower amount in the bladder. Complementation of the mutant with a plasmid containing the wild-type gene restored the expression of PhoU and alkaline phosphate activity to wild-type levels and no significant difference in colonization was observed between the mutant containing the complementing plasmid and wild-type in competitive colonization experiments. In human urine, the mutant and wild-type grew comparably when inoculated independently, indicating that the attenuation observed was not due to a general growth defect. However, as observed , the wild-type out-competed the mutant in competition growth experiments in human urine. These data indicate that PhoU contributes to efficient colonization of the murine urinary tract and add PhoU to a short list of confirmed urovirulence factors.

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2006-01-01
2019-10-14
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