RELATIONSHIP BETWEEN PATHOGENICITY AND pH TOLERANCE OF MICROORGANISMS.

An alkaline medium (Sabouraud's dextrose or maltose agar of pH 10.5) was found to be selective for dermatophytes in the presence of the rapidly growing saprophytic fungi and has been used to isolate dermatophytes from mixed cultures and leather. Virulent dysentery bacteria are able to grow in media of alkaline pH values, while non-virulent strains of the same microorganisms are inhibited completely or very greatly. It is strongly indicated that pathogenicity may be related to pH tolerance and it is suggested that this relationship may be explained by the presence of a trypsin-like enzyme or enzyme system, while a loss of pathogenicity is associated with a loss or weakening of this enzyme system.