Evaluation of different systems for the identification of Bacillus strains isolated from Spanish fermented sausages

Abstract

Sixty-nine isolates obtained during the manufacture and ripening of Spanish fermented sausages were identified to species level using the Vitek Bacillus biochemical card, the dichotomous key and table proposed by Berkeley et al. ((1984). In Methods in Microbiology, Vol. 16. Academic Press, London, p. 291), morphological and physiological tests and the API 20E miniaturized system. None of the tested systems was entirely satisfactory and the final identification was mainly done on the basis of cellular morphology and the table of test results. Our isolates belonged to the species: B. subtilis (37), B. megaterium (22), B. pumilus (5), B. circulans (3) and unidentified (2). Forty-five cultures (65.2%) were accurately identified with the dichotomous key. A similar figure for the Vitek Bacillus biochemical card was 36%. The results of the API 20E system were very reproducible, especially those of the Voges-Proskauer test. Most of the strains of B. megaterium were misidentified as B. subtilis with the dichotomous key. On the other hand, a high percentage of the cultures belonging to B. subtilis were misidentified as B. megaterium with the Vitek system.