On 2 previous occasions reports from this laboratory have described the results of the application of a plate screening technique to the determination of the antibiotic sensitivity of a large number of organisms isolated from clinical materials.1,2 The first covered the period from May of 1950 through March of 1953, and the second from May of 1954 through August of 1955.
It seemed worthwhile to review the results obtained during another interval, from October of 1957 through June of 1959, when the laboratory was closed and the work transferred from San Francisco to the new Stanford Medical Center in Palo Alto, Calif. It was believed that a comparison of the results of testing in the 3 periods might provide information as to whether patterns of resistance of antimicrobial agents were changing.
During the first period only penicillin, streptomycin, tetracycline, and chloramphenicol were employed. Erythromycin, neomycin, and polymyxin were added