Nitrogen-deficient Medium in the Differential Isolation of Klebsiella and Enterobacter from Feces

On a nitrogen-deficient agar medium, the tribe Klebsielleae formed large, glistening, mucoid colonies which were easily distinguished from other colony types. Of 113 Klebsielleae isolates from human feces which were characterized, Klebsiella accounted for 88% of the total; 75% were K. pneumoniae; K. ozaenae (13%) was isolated from one individual only. The remaining strains (12%) were identified as Enterobacter cloacae. Counts (for the tribe) ranged from 10(2) to 10(6), with a median of 10(4); 9 of 53 stool specimens were negative. K. pneumoniae was also isolated from 6 of 41 frozen foil-pack foods. Anaerobic studies at room temperature and 37 C revealed no appreciable differences from aerobic plates. The nitrogen-deficient medium appeared better than E M B for isolation of Klebsielleae when they were present in low numbers relative to other coliforms; slime production by Klebsielleae concomitant with minimal growth of other bacteria is involved.