Isolation and Selection of Bacillus pumilus against Colistin-Resistant Escherichia coli F4

The emergence of antibiotic-resistant Escherichia coli, a major causative agent of diarrhea in piglets, presents significant challenges in the swine industry. Bacillus pumilus, widely recognized for its probiotic potential, has been utilized to promote growth performance, enhance immune responses, and inhibit various pathogens in livestock. This study aimed to isolate and characterize B. pumilus with probiotic characteristics from healthy pigs in Hanoi and Hung Yen. A total of three B. pumilus strains were isolated using a routine culture method, PCR, and MALDI-TOF mass spectrometry. The results revealed that all the isolated B. pumilus strains showed non-hemolytic activity on blood agar. The isolates also exhibited high tolerance in acidic (pH 3.0) and bile salt (0.3%) conditions, with survival rates ranging from 77.97% to 95.38% and 82.61% to 93.62%, respectively. Antimicrobial susceptibility tests revealed resistance to tetracycline and erythromycin, while all isolates were also strongly antagonistic to E. coli F4, with inhibition zones ranging from 16-19mm. Overall, the three B. pumilus isolates demonstrated promising probiotic and antibacterial characteristics, highlighting their potential as alternative agents to control E. coli F4 infections in piglets.