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Bovine Mastitis-Derived Bacillus cereus in Inner Mongolia: Strain Characterization, Virulence Factor Identification,
Chen Yu1,2, Kollie Helena Vivian1,2, Shuangyuan Fan1,2
1Joint International Research Laboratory of Agriculture and Agri-Product Safety, Ministry of Education of China, Yangzhou University, Yangzhou 225009, China.
Veterinary Sciences
|November 26, 2025
Summary
Bacillus cereus is a growing threat in Inner Mongolian dairy herds, causing bovine mastitis. This study reveals its resistance to common antibiotics and highlights the link between specific virulence genes and disease severity.
Area of Science:
- Veterinary Microbiology
- Epidemiology
- Antimicrobial Resistance
Background:
- Bovine mastitis poses significant economic and animal welfare challenges in dairy production.
- Bacillus cereus (B. cereus) is increasingly recognized as a pathogen in bovine mastitis, but its epidemiological characteristics and virulence factors in specific regions require further investigation.
Purpose of the Study:
- To investigate the epidemiological features of B. cereus in bovine mastitis in Inner Mongolia.
- To determine the antimicrobial resistance patterns and virulence gene profiles of B. cereus isolates.
- To assess the clinical implications of virulence factors in B. cereus-associated mastitis.
Main Methods:
- Cross-sectional study involving 340 bacterial isolates from 108 cows with clinical mastitis across three dairy farms.
- Bacteriological analysis, antimicrobial susceptibility testing (Kirby-Bauer disk diffusion), and PCR for virulence gene profiling.
- Murine challenge experiments to evaluate pathogenicity based on virulence factor presence.
Main Results:
- B. cereus was the predominant pathogen (30.58%), followed by Staphylococcus spp. (21.76%).
- High resistance was observed for tetracycline, cotrimoxazole, and ciprofloxacin; complete sensitivity to gentamicin, amikacin, and roxithromycin.
- All isolates carried nheA, nheB, and entFM genes; bh1D was present in 21.15%. Strains with more virulence factors showed increased pathogenicity in murine models.
Conclusions:
- B. cereus is an emerging virulent pathogen in Inner Mongolian dairy herds, contributing to bovine mastitis.
- Antimicrobial stewardship and surveillance of virulence factors are crucial for effective mastitis management.
- Epidemiological data from this study can guide veterinary practices and intervention strategies.
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