Hoyles Media Plate with supplements

Principle And Interpretation

The most common disease caused by Corynebacterium diphtheriae is diphtheria, an acute communicable disease manifested by both local infection of the upper respiratory tract and the systemic effects of the toxin, which are most notable in the heart and peripheral nerves (1). Hoyle Medium Base, formulated by Hoyle (2), is the modification of the original formulation of Neill, for the isolation and differentiation of C. diphtheriae. This medium is not inhibitory to some mitis types of Corynebacterium, as the original formulation.
Peptone and HM peptone B supply carbon, nitrogen, substances, amino acids, vitamins and other essential growth nutrients. Potassium tellurite is a selective agent, which inhibits most of the normal flora of the upper respiratory tract except Corynebacterium. Hoyle’s Medium is a highly selective medium and should be used in conjunction with a non-selective medium such as Loeffler Serum Medium (M037) and Blood Agar Base (M089) with 10% horse blood (3). C. diphtheriae are usually present as small numbers permitting the formation of well-isolated colonies. So, specimens are done by directly rubbing the swab over the entire surface of the medium. Incubation should be carried out till 72 hours if the results are negative. To study the morphology, gentian violet solution is done. To demonstrate the characteristic morphology and staining reactions of C. diphtheriae by Neissers or Alberts method, it is advisable to use colonies from Loeffler Medium. The toxigenicity of C. diphtheriae strains can be determined by Eleks (4) method.