This study was concerned with the examination of 120 strains of Gram-aegative bacilli belonging to the Klebsiella group isolated from patients observed over a one-year period who were suffering with infections owing to these organisms. The identification of these organisms was based on the criteria set forth in the most recent report of the Subcommittee on Taxonomy of the Enterobacteriaceae1 and of Edwards and Ewing.2 In general, these organisms were nonmotile, Gram-negative, encapsulated bacilli which fermented glucose, lactose, and sucrose. They did not produce H2S and were indole negative. They did utilize ammonium citrate as the sole source of carbon but failed to decarboxylate ornithine.
Sixty-three strains were isolated from the urinary tract, 38 strains from the respiratory system, and 19 strains from other sources. Of the 38 strains isolated from the respiratory system, 34 were obtained from nasopharyngeal secretions and sputum, 2 from pleural fluid, and 2 from lung tissue taken at autopsy. Of the 19 strains isolated from