The anti-biofilms effects of Thymus algeriensis on isolated strains of Bacillus cereus

The ability of some microorganisms to form biofilms has been increasing in recent years. Indeed, biofilms are defined as a way of life that allows bacteria to survive and resist in hostile environments. Therefore, this form of survival represents a major problem for different food industries, including the dairy industry. The objective of this study is the isolation of Bacillus cereus strains from raw cow's milk and the study of their characterization, their ability to form biofilms, as well as the search for an inhibitory effect of the essential oil of 'Thymus algeriensis' on these formed biofilms. For this purpose, samples of cow's milk are collected from the region of Abu El Hassan (Chlef) and submitted to microbiological analyses. The preliminary identification of the isolated bacteria allowed the selection of 06 strains of Bacillus cereus. These strains in question have shown great potential for the formation of biofilm in the wells of a micro plate. The formation of biofilm in the micro plate was analyzed first by a simple observation with the naked eye of the wells after coloration with purple crystal, then using an ELISA device where the absorbance of the populations at 620 nm could be measured. Regarding the in vivo effect of the Thymus algeriensis essential oil, a complete inhibition of the biofilm formed was obtained after 24 hours of contact.