Hoyle Medium Base, the well known modification of Neills medium for the cultural isolation and differentiation of Corynebacterium diphtheriae types. Toxigenic strains of Corynebacterium diphtheriae secrete a potent exotoxin which may cause diphtheria. Diphtheria is most commonly an infection of the upper respiratory tract and causes fever, sore throat, and malaise. Corynebacterium diphtheriae is classified into biotypes (mitis, intermedius, and gravis) according to colony morphology, as well as into lysotypes based upon corynebacteriophage sensitivity. Hoyle medium does not exert the inhibitory effect manifested by Neills on some mitis types, but gives very rapid growth with all types of Corynebacterium diphtheriae, so that diagnosis is possible after 18 hours incubation. This is a highly selective medium which is used in parallel with non-selective media such as Blood Agar Base (Cat. 1108) with 5-10 % of sterile defibrinated blood. Unlike non-selective media, Hoyle medium should be inoculated by rubbing the throat swab (or other material) over the entire surface-preading with a platinum loop is not necessary. Beef extract and peptic digest of animal tissue provide nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Bacteriological agar is the solidifying agent.
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