Evaluation of Single and Multi-Strain Probiotics with Gentamicin Against E. coli O157:H7: Insights from In Vitro and In Vivo Studies

The emergence of antibiotic-resistant food-borne pathogens, especially Escherichia coli O157:H7, highlights the urgent need for innovative treatment strategies, particularly in light of rising resistances and the ongoing controversy surrounding antibiotic use in response to E. coli O157:H7 infections. To address this issue, we explored the potential of single- and multi-strain probiotics, both independently and in combination with gentamicin, through a series of in vitro and in vivo experiments. In vitro, gentamicin alone produced a mean inhibition zone of 12.9 +/- 2.27 mm against E. coli O157:H7. The combination of gentamicin with single-strain probiotics (P1) increased the inhibition zone to 16.5 +/- 2.24 mm (p < 0.05), while the combination with multi-strain probiotics (P2) resulted in the largest inhibition zone of 19 +/- 2.8 mm (p < 0.05). In vivo, mice infected with E. coli O157:H7 and treated with P2, gentamicin (G), or their combination (G+P2), achieved 100% survival, no pathological symptoms, and full weight recovery within seven days. Conversely, mice treated with P1 or G+P1 exhibited lower survival rates (71.4% and 85%, respectively) and slower weight recovery. Hematological parameters improved across all groups, but kidney function analysis showed significantly higher serum creatinine levels in the P1, G, G+P1, and G+P2 groups compared to the P2 group (P1: 0.63 +/- 0.15 mg/dL; G: 0.34 +/- 0.09 mg/dL; G+P1: 0.53 +/- 0.19 mg/dL; G+P2: 0.5 +/- 0.23 mg/dL vs. P2: 0.24 +/- 0.2 mg/dL). Histological analysis showed better intestinal and kidney tissue recovery in the P2 group, while the P1 and G+P1 groups exhibited abnormal ileal structures and severe cortical bleeding. These findings highlight the promise of multi-strain probiotics, alone or in conjunction with antibiotics, as a therapeutic strategy for E. coli O157:H7 infections. However, the nephrotoxicity associated with gentamicin co-administration remains a limitation, warranting further studies to optimize this approach.