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Chapter 19

Culture Media for the Isolation of Campylobacters, Helicobacters and Arcobacters

The history of the development of selective media for isolation of campylobacters, including the rationale for choice of selective agents, is described. Most important with regard to human disease are the thermotolerant species C. jejuni, C. coli, C upsaliensis and C. lari. Developments have included modifications to allow incubation at 37°C instead of 42 or 43°C and changes in the types and concentrations of antibiotics in order not to inhibit organisms such as Campylobacter upsaliensis, C. jejuni subsp. doylei and some strains of C. coli and C. lari. When examining foods, plating media originally developed for isolation from faeces are normally used, sometimes after liquid enrichment. Most of the media include ingredients intended to protect campylobacters from the toxic effect of oxygen derivatives. Most commonly used are lysed or defibrinated blood, charcoal, a combination of ferrous sulfate, sodium metabisulfite and sodium pyruvate (FBP) and also haemin or haematin.

Enrichment media are sometimes incubated for a few hours at reduced temperature or addition of antibiotics is sometimes delayed in order to avoid inhibitory effects on sublethally damaged cells from toxic components in the formula. The current ISO method for foods in general recommends the use of Bolton broth and modified charcoal, cefoperazone deoxycholate agar. There is a similar ISO method for water which uses Preston broth as well as Bolton broth. For some foods, particularly raw poultry products that can often be contaminated with large numbers of campylobacters, direct plating as well as enrichment plating is recommended, including a second plating medium.

Media for isolating arcobacters are similar to those for campylobacters, except that lower temperatures and sometimes aerobic atmosphere are used for incubation. Some strains of Arcobacter cryaerophilus and A. skirrowii are sensitive to 32 mg L−1 cefoperazone and all Arcobacter spp. are sensitive to colistin used in some campylobacter media.

Helicobacter spp. are more difficult to cultivate that the other two genera. Selective media for H. pylori have been developed, although, with one exception using immunomagnetic beads, they have not been successful in isolating the organism from foods or the environment. Many other Helicobacter-like organisms, seen in gastric or intestinal tissue samples from a variety of animals, have not been successfully cultivated until recently. H. pullorum can be cultivated on blood agar, while more elaborate methods have been found necessary for other species, including H. bizzizeronii, H. suis and H. baculiformis.

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06 Dec 2011
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