Hoyle's Medium

LAB 27

Description

A highly selective culture medium for the isolation and differentiation of Corynebacterium diphtheriae types gravis, mitis and intermedius. Hoyle's medium gives rapid growth of all types of C. diphtheriae, which results in most specimens giving adequate growth with overnight incubation.

Method of Reconstitution

Weigh 37 grams of powder and disperse in 1 litre of deionised water. Allow to soak for 10 minutes, and sterilise by autoclaving at 121˚C for 15 minutes. Cool to 47˚C, add 50ml of lysed horse or sheep blood and 10ml of X027 potassium tellurite solution. Mix well before pouring.

Appearance: Dark Red, clear gel. pH: 7.8 ± 0.2

Inoculation

Spread the entire surface with the swab or sample under investigation. Hoyle's medium is very selective and spreading for single colonies using a wire loop is not necessary. Use of a non-selective blood agar alongside Hoyle's is recommended.

Incubation: 37˚C for 18-48 hrs, aerobically

Storage: Plates - up to 7 days at 2-8˚C

Minimum Q.C. Organisms C. diphtheriae var mitis (non-toxigenic) E. coli NCTC 10418 (inhibition)

Reference:

Hoyle L. (1941) A Tellurite Blood Agar Medium for the Rapid Diagnosis of Diphtheria. Lancet 1 175-176

176. Elek S.D. (1948) The Recognition of Toxigenic Bacterial Strains in vitro. Brit. Med. J. 1 493-496.