Efficacy of Moricins Extracted from Silkworm against Multidrug-Resistant Bacillus cereus Strains

The rising threat of multidrug-resistant Bacillus cereus compromises food safety and public health, necessitating alternative solutions. Moricins from silkworm show promise, but research on their efficacy against MDR B. cereus is limited, highlighting a critical knowledge gap in developing natural antimicrobial agents for food safety and biocontrol strategies. This study investigated the prevalence of B. cereus in powdered soybean and evaluated the antibacterial activity of moricins extracted from silkworm (Bombyx mori) against multidrug-resistant (MDR) isolates. A total of 100 powdered soybean samples were collected from various retail outlets and screened for B. cereus using standard microbiological methods. Moricins were obtained through solvent extraction and chromatographic purification. The agar-well diffusion method was employed to assess inhibitory activity against three identified B. cereus strains: FORC6 (BCFOR), DQ01 (BCDQO), and CD3 (BCCD3). The isolates exhibited typical Bacillus morphology and biochemical profiles, and molecular analysis confirmed 100% sequence identity with reference genomes. Antibiotic susceptibility testing revealed multidrug resistance, particularly in BCCD3 (75%), followed by BCFOR (37.93%) and BCDQO (29.41%). Moricins demonstrated concentration-dependent inhibitory activity, with detectable effects beginning at 0.40–0.50% and maximal inhibition at 0.90–1.00%, effectively suppressing growth even in highly resistant strains. These findings indicate that silkworm-derived moricins are potent natural antimicrobial agents capable of overcoming multidrug resistance in B. cereus, highlighting their potential application in food safety and biocontrol strategies.