Epimerizes UDP-galactose to UDP-glucose. May contribute to formation of LPS or the exopolysaccharide slime layer by providing UDP-galactose as a substrate for either molecule. UDP-alpha-D-glucose = UDP-alpha-D-galactose Addition of NAD/NADP does not result in differences in enzymatic activity. Gene transcripts were detected at ten days post-infection in chicken yolk sacs infected with strain Breinl. Belongs to the polysaccharide synthase family.