MYCIN, an early expert system developed at Stanford University in 1972, aimed to assist physicians in diagnosing and treating bacterial infections. Using a knowledge base of over 600 rules on infectious diseases and a backward-chaining inference engine, MYCIN diagnosed infections and recommended antibiotics. A breakthrough in artificial intelligence, MYCIN significantly influenced the development of expert systems. It was among the pioneering medical AI systems evaluated in a clinical setting. In a study at Stanford University Medical Center, MYCIN achieved 95% accuracy in diagnosing bacterial infections and recommending antibiotics.