Stewart used Oxoid MacConkey Agar as the basis of a selective-diagnostic medium for pectinolytic organisms, in order to isolate soft-rot Erwinia species from specimens containing other Enterobacteriaceae. Pasteurella species (including Pasteurella multocida) will not grow on MacConkey Agar. Yersinia pestis, Yersinia pseudotuberculosis and Yersinia enterocolitica will show growth on MacConkey Agar after 24 hours incubation at 35☌ 5. MacConkey Agar can be used to differentiate Yersinia species from Pasteurella species 4. The presence of enterococci in azide or tellurite media may be confirmed by subculture on MacConkey Agar. Colonies composed of Gram-negative non-sporing rods are subcultured for further identification. The medium may be used for the direct count of coli-aerogenes bacteria, using pour-plates prepared from known volumes of the water sample, but a more exact role for the medium is for the differentiation of organisms producing acid and gas in MacConkey Broth at 35☌: all positive broth tubes are plated on MacConkey Agar, the plates are incubated for 24 hours at 35☌ and examined for typical colonies (see below). MacConkey Agar should be used in parallel with other selective indicator media such as Desoxycholate Citrate Agar, Bismuth Sulphite Agar, Brilliant Green Agar and Brilliant Green Bile (2%) Broth, and a non-selective medium such as Blood Agar. It provides a number of other diagnostic indications in addition to bile tolerance, such as colony morphology and chromogenesis. Whilst it is selective it does not suppress a mixed bacterial flora to the same extent as other inhibitory media (including other MacConkey agars). staphylococci and enterococci) as well as Enterobacteriaceae, MacConkey Agar is particularly recommended for the cultivation of pathogens which may be present in a variety of specimens such as urine, faeces and wound swabs. of Health 2 and by Windle Taylor 3 for the bacteriological examination of water.Īlthough principally used for coliforms, this medium may also be employed for the differentiation of other enteric bacteria (including pathogens) and is suitable for the differentiation of Pasteurella species 4.ĭue to its ability to support the growth of pathogenic Gram-positive cocci (e.g. MacConkey Agar corresponds to the medium recommended by the World Health Organization 1, the Dept. Dry the surface of the gel before inoculation.Ī differential medium for the detection, isolation and enumeration of coliforms and intestinal pathogens in water, dairy products and biological specimens. Sterilise by autoclaving at 121☌ for 15 minutes. Bring to the boil to dissolve completely. Suspend 52g in 1 litre of distilled water. * Adjusted as required to meet performance standards A differential medium for the isolation of coliforms and intestinal pathogens in water, dairy products and biological specimens.
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