Foodborne diseases have been witnessing a constant rising trend worldwide, mainly caused by pathogenic microorganisms, such as Bacillus spp., posing a direct threat to public health. The purpose of this study was to evaluate the biological risk of foodborne and probiotic Bacillus spp. in Beijing markets. A total of 55 Bacillus isolates, including 29 B. cereus, 9 B. licheniformis and 7 B. subtilis, mostly found in dairy products (32.7%), were recovered from 106 samples and identified by matrix-assisted laser desorption/ionization mass spectrometry and polymerase chain reaction methods. The susceptibility towards 16 antibiotics was determined using a broth microdilution method. Bacillus showed a high level of resistance to florfenicol (100%), lincomycin (100%), tiamulin (78.2%) and ampicillin (67.3%), while they were all susceptible or intermediate to vancomycin and rifampin. Additionally, we obtained the whole genome of 19 Bacillus strains using high-throughput sequencing, and the rates of resistance genes van, fosB, erm and tet were 57.9%, 57.9%, 21.1% and 26.3%, respectively. Moreover, 100%, 9.1%, 45.5% and 100% of these isolates carried virulence genes nhe, hbl, cytK and entFM, respectively. Lastly, 60% Bacillus strains were positive in hemolysis tests, and 3 B. licheniformis strains displayed an inhibitory activity on the growth of S. aureus ATCC 29213 using agar overlay technique. Our study outlines the characteristics of foodborne Bacillus spp. and provides information for the monitoring of food safety.

Background: Soybean meal is used in animal feeds as a protein supplement but contains significant amounts of anti-nutritional factors such as trypsin inhibitor that directly inhibit digestion, absorption and utilization of nutrients. Results: Herein, we used solid state batch fermentation of soybean meal using Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae alone and in combination to alter the content of anti-nutritional compounds in the meal. A systematic analysis identified a temperature of 40℃, water content of 40 % in a 48 h fermentation that optimized the fermentation according to our goals. The digestibility of the meal increased within 36 h and by 48 h, the free amino acid content increased while glycinin, β-conglycinin and trypsin inhibitor significantly decreased and the indigestible sugars stachyose and raffinose were reduced to undetectable levels. These processes correlated with high levels of lactic acid that were responsible for an overall pH decrease. Conclusions: Bacterial and mixed fermentations increased nutritional content while eliminating anti-nutritional factors and significantly improved the nutritional quality of the soybean meal.

Avibacterium paragallinarum-associated infectious coryza (IC) is an important threat in commercial poultry. Previous studies about the characteristics of A. paragallinarum are succeeded in revealing the course of IC disease, but whether and how resident microbes contribute to the infection remains unclear. To understand the role of commensal bacteria, we isolated 467 commensal bacteria, including 38 A. paragallinarum, from the respiratory tract of IC chicken. The predominant commensal isolates were Gram-positive bacteria belonging to Staphylococcus spp. [33.19%, 95% confidence interval (CI): 28.93–37.66%], Enterococcus spp. (16.49%, 95% CI: 13.23–20.17%), and Bacillus spp. (16.27%, 95% CI: 13.04–19.94%). These isolates were closely correlated with the survival of A. paragallinarum. We examined and found that commensal bacteria aggravate A. paragallinarum-associated infections because certain commensal species (28.57%, 95% CI: 15.72–44.58%) induced hemolysis and promoted the growth of A. paragallinarum in vitro. Notably, A. paragallinarum showed high resistance to routine antibiotics such as erythromycin (84.21%, 95% CI: 68.75–93.98%), tetracycline (73.68%, 95% CI: 56.90–86.60%) and carried diverse mobile resistance gene clusters. Overall, we found commensal bacteria especially Gram-positive bacteria facilitate the survival of multidrug-resistant A. paragallinarum to exacerbate infections, suggesting that novel strategies may diminish A. paragallinarum-associated infections by modulating the population dynamics of commensal bacteria.