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Lee and Son(1955) observed that certain stains of mycobacteria grown on Ogawa medium containing soluble extract of fruit of Fructose gardeniae produced dark violet pigment around the colonies (referred to crocin reaction). Thereafter, the crocin reactions with atypical mtcobacteria, (Choi et al.,1974) β-hemolytic streptococci(Seok et al.,1976) and Bacillus subtilis(Kim, 1978)have been reported. In this study the crocin reaction of various human pathogenic bacteria was investigated. In addition, with Lancefield groups of β-hemolytic streptococci the diagnostic value of presumptive tests of Lancefield grouping, a modified CAMP test and crocin test was studied. In thw summary, of 9 species of gram-positive bacteria tested, all strains of Bacillus subtilis and 12 strains of 44 strains β-hemolytic streptococci were positive in the crocin reaction. respectively. Of 13 species of gram-negative enteropathogens, Enterobacter aerogenes was a single species that was positive in the crocin reaction. The crocin reaction was not observed with small gram-negative bacilli, i.e.,B.abortus,B. bronchiseptica, B. pertussis, Y.peslis, P. multocida and H. vaginalis. In the crocin reaction with Lancefield groups of β-hemolytic streptococci, positive reactions were observed with group B,D and G, but neither group A nor C showed the crocin reaction. All strains of groupp B,D and G streptococci which produced green hemolysis on human blood agar showed positive crocin reaction, whereas they all showed negative CAMP reaction. The growth of the most species of bacteria, except for B. abotus, B,pertussis and H. vaginalis appeared to be enhanced resulting in the development of larger colonies on the BHI agar containing soluble extracts of fructose gardeniae and the most clocies showed mucoid type appearance. This results indicated that the crocin test would of value for a rapid differentiation of pathogenuc strains of B. anthracis from nonpathogenic strains of B. subtilis, of Lancefield group A of β-hemolytic streptococci from other groups, and of Enterobacter aerogenes from other rapid lactosefermenting gram-negative enterpathogens, i.e., Escherichia coli and Klebsiella pneumoniae.
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