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Pakistan Journal of Biological Sciences

Year: 2001  |  Volume: 4  |  Issue: 12  |  Page No.: 1547 - 1549

Optimizing Recovery of Listeria Species from Imported Frozen Beef

Endang Purwati, Zaiton Hassan, Gulam Rusul, Raha Abdul Rahim and Son Radu

Abstract

The objective of present work was to optimize the procedures of FDA and USDA for the isolation of Listeria species in imported frozen beef samples marketed in Malaysia. The modifications consisted of direct analysis or storage of samples at 4°C for 24 h prior to analysis, and enrichment at 30°C or 35°C for 24, 48 and 168 h. For both FDA and USDA modified methods, storage at 4°C for 24 h and pre-enrichment at 24 and 48 h were the most efficient. However, the modified FDA with storage at 4°C for 24 h and pre-enrichment for 24 h (30°C and 35°C) and 48 h (30°C and 35°C) yielded more Listeria species. The rates of isolation were markedly affected with prolonged pre-enrichment incubation up to 168 h. The overall conclusion was that the modified USDA isolation method is beneficial when a limited range of the clinically important Listeria species is sought, whilst the modified FDA is needed to estimate the prevalence of Listeria species in the samples examined.

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