After an overnight inoculation at 37 8C, colonies with beta hemolysis an 5% sheep blood agar but no growth with B, were inoculated to 5% sheep blood agar again and antibiogram identification discs containing 0.04 U B and 1.25 and 23.75 mg SXT (Oxoid, UK) were placed onto the plate and incubated overnight at 37 8C.