A mutual insurance company which has merged or consolidated with a hospital service association shall not terminate its contract entered into under Chapter 1739. of the Revised Code with a hospital based upon such hospital’s charges in relation to the charges of other hospitals operating in the same geographical area, where such hospital is the only osteopathic hospital operating in a county in this state. For purposes of this section, “osteopathic hospital” means one in which more than seventy-five per cent of the physicians are licensed osteopathic physicians.