New Probiotic Strain Shows Risks of Antibiotic Resistance
Genomic analysis reveals resistance genes in the S8 strain, complicating its potential use as a poultry growth additive.
Updated on Oct. 27, 2026 in Life Sciences
Researchers have completed genomic and phenotypic analysis of the Limosilactobacillus reuteri S8 probiotic strain, identifying significant antimicrobial resistance. The study, which remains at the research stage, warns that these traits may limit the strain's commercial use as a probiotic.
Why it matters
As the agricultural industry shifts away from antibiotic growth promoters in poultry, finding safe, effective probiotics is increasingly urgent. This study highlights that some strains may carry hidden resistance genes, complicating their safety profile for wide-scale deployment.
The S8 strain demonstrated 85% survival in pH 3.0 conditions and 50.5% growth in 0.3% bile salts. Genomic analysis further identified 155 strain-specific gene clusters and the presence of acquired antimicrobial resistance genes including tet(W), tet(L), and lnu(A).
The players
National Institute of Genetic Engineering and Biotechnology
A research facility that conducted the phenotypic analysis and handled the laboratory protocols for the study.
The details
Researchers performed whole-genome sequencing and comparative pan-genomics—an analysis of the entire set of genes across a species—to characterize the strain. The S8 strain also underwent in vitro assays to test adherence to Caco-2 cells, a common line of human epithelial cells used to model the intestinal barrier for potential competitive exclusion, where a probiotic prevents pathogens from occupying host tissue. While the strain showed antagonistic activity against Salmonella enterica and Escherichia coli, its resistance to tetracycline and ampicillin suggests safety risks for commercial application.
Timeline
October 27, 2026: The study detailing the findings was officially published.
The Tech Race
This development follows the global regulatory ban on antibiotic growth promoters in poultry, which intensified the search for viable microbial alternatives. The findings highlight that identifying a candidate is only the first step in a race to prove safety against established antibiotic resistance standards.
The current results categorize this strain as unsuitable for immediate commercial use, meaning it will not appear in poultry feeds or supplements anytime soon. Further in vivo verification is required to confirm whether this strain can successfully outcompete pathogens in a living host.
The takeaway
Probiotic development requires rigorous genomic screening to ensure strains do not inadvertently carry mobile resistance genes into the food supply. Stakeholders should monitor subsequent in vivo trials to see if researchers can isolate or engineer safer variants of the S8 strain.
Further reading
For broader trends in research into microbial health, visit our Life Sciences section.
Source note: This article includes information reported by Nature.
