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

On a nitrogen-deficient agar medium, the tribeKlebsielleae formed large, glistening, mucoid colonies which were easily distinguished from other colony types. Of 113Klebsielleae isolates from human feces which were characterized,Klebsiella accounted for 88% of the total; 75% wereK. pneumoniae; K. ozaenae (13%) was isolated from one individual only. The remaining strains (12%) were identified asEnterobacter cloacae . Counts (for the tribe) ranged from 102 to 106 , with a median of 104 ; 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 ofKlebsielleae when they were present in low numbers relative to other coliforms; slime production byKlebsielleae concomitant with minimal growth of other bacteria is involved.