A Rapid Differential Method for the Isolation of Bacillus Influenzæ

I t has often been noted that on a blood agar plate seeded with influenzal sputum the colonies of Bacillus influenz6e are most numerous and grow to larger size in the neighborhood of colonies of certain other organisms, notably the staphylococcus. This phenomenon led the authors to conduct various experiments which may be summarized as follows: Blood agar plates were seeded uniformly with a pure culture of Bacillus influen~.6e and were then streaked with hemolytic and non-hemolytic staphylococci, hemolytic and non-hemolytic streptococci, and hemolytic and non-hemolytic strains of Micrococcus catarrhalis. After incubation it was found that the more luxuriant growth of Bacillus influemce occurred only in the neighborhood of the streaks of hemolytic staphylococci, streptococci, and micrococci, not in the neighborhood of the non-hemolytic strains. On laked blood agar the colonies of Bacillus influenzce grew well throughout the plate and were no more numerous in the vicinity of staphylococcus, streptococcus, or micrococcus streaks than elsewhere. I t has been shown I that the well known zones of hemolysis produced by hemolytic streptococci in blood agar are largely if not entirely the result of mere laking of the blood corpuscles and outward diffusion of the released hemoglobin into the surrounding medium. We would conclude, therefore, that the more luxuriant growth of Bacillus influenzce in the neighborhood of colonies of hemolytic cocci is the