Hill & Knowlton’s Paul Oestreicher is taking over as head of Zeno Group, the Chicago-based healthcare PR firm, following Charlotte Wray’s defection to Omnicom startup Mosaic Health Communication. Wray, who spent five years at Zeno Group, an Edelman company formerly known as PR21, was most recently managing director and head of the firm’s New York office. She said the move was “a great opportunity to create something out of nothing.” Mosaic will be the healthcare arm of a new Omnicom PR conglomerate comprised of consumer technology shop Brodeur and several other mid-sized agencies. Wray hopes eventually to extend the startup’s business to medical communications, recruitment and retention strategy, and said she was drawn to Omnicom’s “people-centric and entrepreneurial” culture.Oestreicher joined Hill & Knowlton last year from DeVries Public Relations, but previously served as general manager of Edelman Chicago. He has also worked stints at Sanofi-Synthelabo, Wyeth, Genaissance Pharmaceuticals, Hoffman-La Roche and Medicus PR.