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an epidemiological study of listeriosis in dairy cattle

an epidemiological study of listeriosis in dairy cattle

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were also compared with those obta<strong>in</strong>ed at 4 0 C <strong>in</strong> the absence <strong>of</strong> medium. For this<br />

<strong>study</strong> the 20 faecal samples collected <strong>in</strong> October 1994 (20) <strong>an</strong>d <strong>an</strong> additional 79<br />

samples collected <strong>in</strong> March 1995 were used. Cold enrichment was carried out by<br />

keep<strong>in</strong>g samples <strong>in</strong> either sal<strong>in</strong>e, LSEB, nutrient broth (NB) or no medium at 4°C <strong>an</strong>d<br />

cultur<strong>in</strong>g periodically for up to 7 weeks. Isolation <strong>an</strong>d identification was carried out<br />

accord<strong>in</strong>g to the methods given below (Figure 5. 1).<br />

b) Identification procedure: (Appendix 3)<br />

At least five colonies <strong>of</strong> Listeria were picked <strong>of</strong>f the LSA plates <strong>an</strong>d sub-<br />

cultured on 5% Sheep Blood Agar (SBA) or Horse Blood Agar (HBA) plates at 37 0 C<br />

overnight. The follow<strong>in</strong>g tests were carried out to identify the isolates as Listeria<br />

species:- Gram sta<strong>in</strong><strong>in</strong>g, Catalase test, Motility test, Haemolytic activity, CAMP test<br />

<strong>an</strong>d Carbohydrate utilisation. Information provided <strong>in</strong> Table 1. 1. was used to aid<br />

identification.<br />

Fresh sample<br />

Re-culture after Cold enrichment<br />

3 weeks at 4 0 C for 7 weeks<br />

135

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