Counterimmunoelectrophoresis for rapid identification of blood-culture isolates.

A total of 303 blood cultures that were positive by examination of Gram-stained smears were tested immediately by counterimmunoelectrophoresis for detection of bacterial antigens. Antigen was detected in all 82 blood cultures containing Streptococcus pneumoniae and 11 of 22 with Klebsiella pneumoniae, two of two with Haemophilus influenzae, and one of one with Neisseria meningiditis. False-positive cross-reactions in 265 tests occurred only with pneumococcal Omniserum in two cases of nongroupable streptococcal bacteremia and with Klebsiella antiserum in one case of Escherichia coli bacteremia (1.1%). A specific identification of the microorganisms at least 24 hours earlier than by subculture technics was accomplished in 91% of the cultures containing the aforementioned bacteria. The procedure was not useful for detecting antigen in blood cultures containing Staphylococcus aureus.