The Townsend v. Catalina Ambulance Co., 857 S.W.2d 791 (Tex.App.-Corpus Christi 1993, no writ) court held an ambulance service was not expressly listed in section 103(3) and, therefore, was excluded from the definition of "health care provider." Id. at 796.. Under the doctrine of respondeat superior, "an employer is vicariously liable for the negligence of an agent or employee acting within the scope of his or her agency or employment, although the principal or employer has not personally committed a wrong." Baptist Mem'l Hosp. Sys., 969 S.W.2d at 947. We do not read Medical Liability and Insurance Improvement Act to bar suit against an entity which employs physicians to treat patients. TEX. REV. CIV. STAT. ANN. art. 4590i (Vernon Supp. 2000).