Serum resistance properties of Klebsiella pneumoniae and K. oxytoca isolated from different sources.

A total of 481 K. pneumoniae and K. oxytoca strains from different sources was examined with respect to sensitivity to normal human serum. K. oxytoca strains much more frequently proved to be serum resistant than K. pneumoniae isolates. Environmental strains of both species showed greater serum sensitivity than fecal or clinical isolates. While K. oxytoca strains isolated from feces and clinical specimens showed similar frequencies of serum resistant isolates, fecal K. pneumoniae strains less often were serum resistant than clinical K. pneumoniae isolates. Clinical Klebsiella strains appear to be more related to strains isolated from feces than to those isolated from the environment.