Dr. Robert A Zajac has 2 locations. Responsive Infectious Disease 150 E Sonterra Blvd Ste 170 San Antonio, TX 78258. (210) 481-2800. ACCEPTING NEW PATIENTS. Ridge Responsive Id Solutions 150 E Sonterra Blvd Ste 170 San Antonio, TX 78258. (210) 481-2800..