Methods and compositions effective for at least a week for prevention of microbial colony growth on a surface, for example an inanimate surface, where the surface is covered with a dry or substantially dry film formed from a composition comprising a polyvinyl alcohol and a quaternary ammonium compound. The film may be formed in situ by coating the surface with a solution or emulsion comprising a polyvinyl alcohol and a quaternary ammonium compound and then causing or allowing it to dry or substantially dry.