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Staphylococcus saprophyticus is one of the leading causes of urinary tract infections. However, prior to our ancient genome study described above, the genomes of only a few strains had been sequenced. In our previous analysis, we observed a lineage enriched in human pathogenic isolates. To further understand S. saprophyticus adaptation to the human pathogenic niche, I performed selection and demographic analyses on the S. saprophyticus lineage associated with human urinary tract isolates and discovered a selective sweep in a gene encoding the fibronectin binding autolysin Aas, a known virulence factor. We collaborated with Dr. Deane Mosher to confirm that the ancestral and derived versions of Aas bind human and bovine fibronectin and discovered that Aas also binds human thrombospondin. Genome-wide patterns of diversity in the lineage enriched in human isolates are consistent with a selective sweep followed by a population size expansion, consistent with emergence into the human pathogenic niche.

This work is published in mSphere here!