Enterohemolysin production on Beutin's washed sheep blood agar plate has been used as an epidemiological marker for selective screening of Verocytotoxin-producing/Enterohemorrhagic
Escherichia coli(VTEC/EHEC). In this study, we examined about the component of Beutin' s washed sheep blood agar for further improvement of hemolysin production media. The following items were studied: the numbers of washings of sheep blood with phosphate buffered saline (PBS) (pH7.2), concentration of sheep blood, kind and concentration of divalent metal ion (Ca
2+, Mg
2+) and basal medium. Twenty-seven strains of VT-producing
E. coliof 7 different O-serotypes, 74 strains of VT-nonproducing
E. coliof 24 different O-serotypes and one strain of O157 coded
Escherichia hermaniiwere used for this basic study.
In comparison of washing times of sheep blood with PBS, 5 times washing was better than 3 times, the original. In sheep blood concentration, supplement with 4% sheep blood was best for hemolysis observation. In experiment of addition of 2 divalent metal ions, Ca
2+and Mg
2+, supplement with Ca
2+was more suitable than Mg
2+for hemolysis, and the supplement with 10 mM CaCl
2, the original, was the best concentration. On the basal medium used in Beutin's sheep washed blood agar, 4 kinds of media were compared. In addition to Soybean-Casein Digest (SCD) agar, the original, Nutrient agar, Heart Infusion (HI) agar and Brain Heart Infusion (BHI) agar were examined, HI agar was the best blood agar base in the four media.
As the above experimental results, the composition of the better Beutin's washed sheep blood agar may be summarize as follows: Heart Infusion agar ‘Eiken’
®used for blood agar base, supplemented with 10mM CaCl
2 and 4% defibrinated sheep blood (Japan Biosupp. Center) washed five times in phosphate-buffered saline, pH 7.2.
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