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June 1956

Sensitivity of Various Clinically Important Bacteria to Seven Antibiotics

Author Affiliations

San Francisco

From the Department of Medicine, Stanford University School of Medicine.

AMA Arch Intern Med. 1956;97(6):694-702. doi:10.1001/archinte.1956.00250240046004

For several years a screening procedure for estimating the sensitivity of bacteria to antibiotics has been in use in this laboratory. Organisms have been exposed to a single arbitrarily selected concentration of the antimicrobial agent contained in a blood agar plate. Those inhibited have been regarded as sensitive, and those exhibiting growth, as resistant. The clinical correlations have been good.

The results obtained from the study of 720 strains isolated during the two-and-one-half-year period from October, 1950, to March, 1953, have been previously reported.1 Penicillin, streptomycin, oxytetracycline, and chloramphenicol were included in the routine testing. In May, 1954, erythromycin, neomycin, and polymyxin were added to this list and tetracycline was substituted for oxytetracycline. Penicillin and erythromycin were usually omitted in the study of Gramnegative bacilli, as was polymyxin with Gram-positive organisms.

It is the purpose of this report to describe the antibiotic sensitivity of 1698 strains of bacteria, all