Rapid presumptive identification of streptococci directly from blood cultures by serologic tests and the L-pyrrolidonyl-beta-naphthylamide reaction.

The value of the Strepslide kit for the rapid presumptive identification of streptococci directly from blood cultures without prior determination of hemolysis patterns was assessed and compared with that of the Streptex and Phadebact streptococcus kits. Studies involved 94 simulated and 60 clinical isolates of 83 streptococci. The Streptex and Strepslide kits had excellent sensitivity and specificity for group A, B, F, and G organisms, and the Phadebact kit had excellent sensitivity and specificity for groups B and G. Group C reactions usually occurred with all of the streptococcus kits with pneumococci and occasionally with alpha-hemolytic streptococci. Although these kits were unacceptable for group C and D organisms, enterococci which were common clinical isolates could be directly identified in blood cultures by a supplementary rapid L-pyrrolidonyl-beta-naphthylamide biochemical test. Direct application of the Phadebact pneumococcus kit to blood cultures was also assessed with 29 isolates of 20 organisms. The specificity was good, but the sensitivity was only 65.5%.

Improved biochemical screening procedure for small clinical laboratories for vero (Shiga-like)-toxin-producing strains of Escherichia coli O157:H7.

Of 327 sorbitol-negative fecal isolates of Escherichia coli, 37 O157:H7 Vero (Shiga-like)-toxin-producing strains were identified. The specificity of the basic sorbitol screen was improved from 11.3 to 33.6% by the exclusion of organisms with negative ornithine and lysine decarboxylase reactions.