Preliminary Study On Biofilm Characteristics And Formation Mechanism Of Deadly Bacillus Cereus From Cattle

Bacillus cereus belongs to gram-positive bacteria,which is widely distributed and has certain pathogenicity.Bacillus cereus can adhere to the surface of living and non-living organisms and aggregate to form biofilm.The formation of biofilm can enhance the resistance of the bacteria to the external environment and increase the difficulty of its removal.It not only causes serious harm to human and livestock,but also brings huge economic losses to the whole breeding industry.Therefore,it is an urgent problem to understand the growth characteristics of Bacillus cereus biofilm in different stages and explore effective methods to remove Bacillus cereus biofilm.In this study,the ability of Bacillus cereus biofilm formation was identified by crystal violet staining and XTT reduction method.The biological characteristics of the biofilm under different growth conditions were detected by changing p H,Na Cl concentration,glucose concentration,medium concentration and temperature.Different Chinese herbal extracts and antibiotics were selected to determine the minimum inhibitory membrane concentration of five Chinese herbal extracts and antibiotics on Bacillus cereus biofilm by microdilution method.The effects of Bacillus cereus biofilm formation on the pathogenicity of different organs of animals were observed by inoculation test and pathological section.The results showed that Bacillus cereus had good biofilm formation ability and compact structure.The optimum temperature for biofilm formation was 37℃,the optimum p H was 7,0.5% Na Cl,1% and 3% glucose and 200% TSB medium could promote biofilm formation.The minimum inhibitory concentration of baicalin,berberine,panichololide,emodin and sodium houttuynitin on biofilms were 128μg/m L,256 μg/m L,256 μg/m L,256 μg/m L and 512 μg/m L,respectively.The minimum inhibitory membrane concentrations of azithromycin,ampicillin,gentamicin,enrofloxacin and flufenicol for biofilm were 32 μg/m L,64 μg/m L,64μg/m L,64 μg/m L and 128 μg/m L,respectively.The bacteria can make healthy mice infected and die,and cause different degrees of organ damage.This study identified the biofilm formation ability of Bacillus cereus and its growth characteristics under different environmental conditions,and explored the effects of different drugs on its growth,which laid a theoretical foundation for the study of Bacillus cereus biofilm.