Suppressive Effect of Bifidobacterium bifidum Probiotic Supernatant on Tigecycline Resistance Gene Expression in Clinical Isolates of Streptococcus pyogenes

Background: The rapid rise in antibiotic resistance is a grave worldwide concern, with tigecycline being a key treatment here. Inherent resistance is making this common yet sometimes fatal bacterium, Streptococcus pyogenes, difficult to treat. This study looks at whether the liquid from the probiotic Bifidobacterium bifidum can lower the activity of important tigecycline resistance genes: tet(M), tet(O), and tet(X1) in clinical samples of S. pyogenes.
Materials and Methods: A total of 60 S. pyogenes isolates were identified from 100 clinical samples using biochemical methods. The tigecycline susceptibility test was carried out, following standard antibiogram procedures. The antimicrobial potential of the supernatant of B. bifidum was assessed by determining the MIC and MBC values of it.
Results: High resistance against tigecycline was evidenced, with 59% of isolates found to be resistant. The most common gene associated with resistance was tet(M) (16.67%), followed by tet(O) (11.67%), and finally, tet(X1) (1.67%). No isolate carried all three genes together. MIC and MBC values for the probiotic supernatant ranged from 8 to 128 μg/mL and 16 to <128 μg/mL, respectively. Crucially, real-time PCR showed that the supernatant significantly reduced the expression of all three resistance genes in the treated isolates.
Conclusion: These results suggest that B. bifidum supernatant may help suppress tigecycline resistance in S. pyogenes by downregulating the expression of critical resistance genes. This highlights its potential as a natural, supportive strategy to help combat antibiotic resistance and lays the groundwork for future clinical or therapeutic research.