Potential Probiotic Bacillus Strains Isolated from Contaminated Soil in North Macedonia: Salmonella Growth Inhibition

Salmonellosis, which occurs most frequently (85%) as a result of consuming contaminated food, is brought on by salmonellae, which are bacteria that can infect both humans and animals. By assisting with the absorption of some critical nutrients, probiotics have the potential to exert growth-promoting effects by competitively excluding pathogens and boosting feed conversion rates. In the prevention and treatment of Salmonella illnesses, probiotics are seen as an alternative to antibiotics. To utilize probiotica as previously suggested, it is necessary to thoroughly assess their features and choose the bacteria that will work best for the intended purpose. The aim of this study was to investigate the probiotic properties of three Bacillus spp. strains isolated from contaminated soil in North Macedonia and their antimicrobial activity against Salmonella enterica ATCC 10708 using the agar-well diffusion method. For identification, isolates were characterized morphologically and biochemically. Additionally, their ability to survive in the presence of bile salts and at low pH, high osmotic concentrations of NaCl and their susceptibility to antibiotics were examined. The capacity of isolates to metabolize various sources of carbohydrates was also assessed. Each tested strain demonstrated antagonistic activity against Salmonella enterica ATCC 10708. The three different Bacillus strains were all resilient to an acidic environment (pH 3.0) and a high osmotic pressure (NaCl at 6.5%). This research indicates that new Bacillus strains' probiotic qualities are also promising and exhibit strong inhibition activity against Salmonella enterica ATCC 10708.