Page 241 - The Veterinary Laboratory and Field Manual 3rd Edition

210 Susan C. Cork and Roy Halliwell

(a) (b)

Figure 4.6 (a) Anaerobic jar with sealed lid (A) and a GasPak (B). A new pack is used prior to re-incubation
after the lid is removed to examine the culture plates (C). The jar is usually placed in a normal incubator
at 37°C and the plates are examined after 24 and 48 hrs of culture. Illustration: Louis Wood. (b) This is an
example of a chamber used for growth of anaerobic bacteria. The blue pouch in the chamber contains a
palladium catalyst which when water is added generates carbon dioxide and hydrogen gases, reducing
the oxygen concentration to 0–5 ppm, and creating water vapour.

Table 4.2a Media used for the isolation and identification of common bacterial
pathogens.

Medium Comments
Blood agar An enriched medium used to support the primary isolation of a wide range of
bacteria. Also allows detection of haemolysis characteristics e.g. haemolytic
Steptococci and Staphylococci
MacConkey agar Selective medium containing bile to select for Enterobacteria and some other
Gram –ve bacteria. Also allows demonstration of lactose fermentation (+ve
colonies are pink)
Nutrient agar A basic medium useful for non fastidious bacteria. Often used for colony counting
and to demonstrate pigment production
Brilliant green agar A useful indicator medium for the presumptive identification of Salmonellae.
Salmonella spp. appear pink
Chocolate agar Heat treated blood agar with added growth factors (X/V) to support isolation of
Haemophilus sp and Taylorella sp.
Selenite broth Selective enrichment media used for the isolation of Salmonellae
Edwards medium A special blood agar based medium used for the isolation and identification of
Streptococci

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