Hoyles Agar

Hoyles agar is selective culture medium for the isolation and differentiation of Corynebacterium diphtheriae types. Hoyles agar allows for rapid growth of the organisms and normally 18 hours incubation should be sufficient for a diagnosis. As the medium is highly selective, inoculation should be by rubbing the swab (or other material) over the entire surface of the agar, there is no need to spread the inoculum with a loop indeed doing so can cause the organism to be missed especially when they are present only in small numbers. The Elek method can be used to determine the toxigenicity of any C. diptheriae strains.The beef extract and peptone act as a source of nitrogen, carbon and vitamins. The sodium chloride maintains osmotic balance. This medium should be used in conjunction with two supplements: lysed horse blood at 50 ml/l and 10ml/l of potassium tellurite 3.5% solution (BM2230). Lysed horse blood provides added nutrients to the medium and potassium tellurite inhibits Gram-negative and several Gram-positive microorganisms.

Additional InformationShelf Life (days)1095 daysStorage Temp (C)10-30CDehydrated Medium AppearanceFine PowderPrepared Medium AppearanceFirm GelDehydrated Medium ColourBeigePrepared Medium ColourDark RedDehydrated PH7.8 0.2Prepared PH7.8 0.2Recommended IncubationAerobically at 35-37C for 18-48 hoursFormula*g/LBeef extract10.0Peptone10.0Sodium chloride5.0Agar12.0Total37.0*Adjusted/supplemented as required to meet performance requirements