Characterization of Bacillus Species from Convenience Foods with Conventional and API Kit Method: A Comparative Analysis

Abstract

Identification of microorganisms is central to the study of microbiology at all levels/strata of research. The methods employed are also important. It is however pertinent that scientists need to improve on the method of microbial identification for greater efficiency. A study was conducted to isolate and identify Bacillus species from some ready-to-eat food (RTEs) samples. The Bacillus species isolated were identified by using the classical method. Major groups were further identified using the API kits. It was observed that definite identification of some bacilli isolates using these methods was not possible. API system combination of the 50 CHB and 20E was able to identify about 80.0% of the bacilli isolates (16 of 20). The API Bacillus identification system failed to identify 4 isolates of Bacillus thuringiensis. Isolates were identified as B. cereus, B. subtilis, B. megaterium, B. licheniformis, B. sphaericus and B. polymyxa using biochemical tests. On the other hand, use of the API kits showed the identification of B. cereus, B. subtilis/amyloliquefaciens, B. licheniformis/   B. subtilis, B. subtilis/B. pumilus, B. licheniformis, B. megaterium and B. sphaericus. ‘Most likely’ B. thuringiensis from classical identification were identified as other closely related members of the B. cereus group (B. cereus, B. anthracis, B. mycoides and B. pseudomycoides). According to the results of the classical methods B. subtilis was the most abundant species. API kits confirmed B. amyloliquefaciens as the predominant species.