Abstract
Bacillus bacteria have attracted the attention of scientists as promising probiotics because of their versatile antimicrobial activity and established health benefits on the host. In this study, seven Bacillus strains were identified and analyzed for antagonistic activity against broad spectrum of food borne pathogens. All strains were identified as B. subtilis, based on the results of morphological, biochemical characterization and 16S rDNA sequence analysis. B. subtilis strains demonstrated antagonistic activity against test-cultures of pathogens, including multiresistant strains. Reference Bacillus strains, derived from the commercial probiotics did not show antagonistic activity against tested strains of pathogens. Three the most active cultures were studied for production of biosurfactants. Crude biosurfactants were isolated and analyzed by oil spread test and inhibition activity against Salmonella, Shigella and Staphylococcus cultures. Biosurfactants from three tested B. subtilis strains gave positive oil spread test. Inhibition activity of biosurfactants was found only against Staphylococcus strains. Production of biosurfactants depended on the incubation conditions of Bacillus culture. Best results were obtained after cultivation of bacilli in starch broth at 30°C. The concentration of produced biosurfactant increased in time with growth of bacteria and reached the maximum at 30 hours of incubation.
Highlights
Foodborne pathogens are among the most significant problems in maintaining the health of the population
Additional testing with API 50CHB kit resulted in identification of all cultures as B. subtilis
A search for new Bacillus strains with pronounced antagonistic activity against food borne pathogens opens up promising expectations for treatment of these infections
Summary
Foodborne pathogens are among the most significant problems in maintaining the health of the population. The leading causes of foodborne illnesses in the United States are Salmonella and Shigella [1,2]. Staphylococcus aureus is among top five pathogens contributing to domestically acquired foodborne illnesses. Staphylococcal food poisoning is estimated to account for 241,148 foodborne illnesses per year in the United States, according to the CDC information (http://www.cdc.gov/foodborneburden/2011-foodborneestimates.html). Foodborne illnesses are routinely treated with several classes of antibiotics. The use of these antibiotics has become problematic as over the years there have been numerous reports of cases of multi-antibiotic resistant food borne pathogens, worldwide [3,4,5]. In the United States, the proportion of methicillin-resistant S. aureus (MRSA) isolates from patients in intensive care units increased from 1992 to 2003 by 3% per year. Since foodborne infections have a dramatic impact on morbidity and mortality, of infants and children, new approaches for cost effective and easy-to-deliver prophylaxis and treatment of these infections are highly desirable
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