Evaluation of the Bacti-Lab streptococci culture systems for selective recovery and identification of group A streptococci

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Abstract
Twenty-nine lots of Bacti-Lab streptococci culture plates containing nalidixic acid, neomycin and amphotericin B were inoculated with 25 strains of group A, B, C, F and G streptococci, 13 strains of nonstreptococcal bacteria representative of throat flora, and 198 fresh clnical throat specimens to determine the accuracy of the plates in identifying group A streptococci. With the Bacti-Lab test plates 98.87% of the .beta.-hemolytic streptococcal strains tested produced growth, with 95.51% yielding 50 colonies. Of the nonstreptococcal .beta.-hemolytic and non-.beta.-hemolytic organisms tested, 79.54% were inhibited by the selective media. When bacitracin disks were used for presumptive identification of group A streptococci from clinical throat specimens, 12.00% false positive and 0.00% false negative results were obtained as measured by the direct fluorescent-antibody and Lancefield grouping methods.