Hoyle Medium Base, 500 g

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. Peptic digest of animal tissue and beef extract supply essential growth nutrients. Potassium tellurite is a selective agent, which inhibits most of the normal flora of the upper respiratory tract except Corynebacterium . Hoyles Medium is a highly selective medium and should be used in conjunction with a non-selective media such as Loeffler Serum Medium (M537) and Blood Agar Base (M089) with 10% horse blood (3). C.diphtheriae are usually present in small numbers permitting the formation of well isolated colonies. So, inoculation is 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 staining 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. Storage and Shelf-life: Store below 30°C in tightly closed container and prepared medium at 2-8°C. Use before expiry period on the label. References: 1.Murray P. R., Baron J. H., Pfaller M. A., Jorgensen J. H. and Yolken R. H., (Ed.), 2003, Manual of Clinical Microbiology, 8th Ed., American Society for Microbiology, Washington, D.C. 2.Hoyle I., 1941, Lancet., 1:175. 3.MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore. 4.Elek S. D., 1948, Brit. Med. A1:493.