Evaluation of probiotic properties and genome analysis of the new Pediococcus acidilactici strain 46A isolated from Chinese young adults: in vitro and in vivo studies

Polina Makarycheva¹Vincenzo Bellitto¹Aristide Toussaint NGUELE^1,2Chiara Salvesi¹Matteo Mozzicafreddo³Anna-Rita Attili¹Dennis Fiorini⁴Daniele Tomassoni¹Stefania Silvi^1*Cristina Miceli^1*

• ¹Universita degli Studi di Camerino Scuola di Bioscienze e Medicina Veterinaria, Camerino, Italy
• ²Institut Supérieur des Sciences de la Santé, Université Adventiste Cosendai, Nanga Eboko, Cameroon
• ³Universita Politecnica delle Marche Dipartimento di Scienze Cliniche e Molecolari, Ancona, Italy
• ⁴Universita degli Studi di Camerino Scuola di Scienze e Tecnologie, Camerino, Italy

Background: The human gut microbiota plays a key role in intestinal homeostasis and inflammatory diseases, prompting the search for novel probiotic strains with strain-specific functional properties. Differences in dietary habits and cultural backgrounds represent a valuable source for isolating previously uncharacterized gut bacteria. Given the increasing use of probiotics, rigorous safety assessment, including antimicrobial resistance (AMR) evaluation, is required, and the integration of whole-genome sequencing with phenotypic characterization is recommended. Objectives: This study evaluated the probiotic potential of Pediococcus acidilactici strain 46A, isolated from faecal samples of healthy Chinese student volunteers, through whole-genome analysis and in vitro and in vivo functional assessments. Methods: Strain identification was performed by MALDI-TOF mass spectrometry and 16S rRNA gene sequencing. In vitro assays assessed tolerance to simulated gastrointestinal conditions, bile salt resistance, antimicrobial activity, and adhesion to HT-29 intestinal epithelial cells. Whole-genome sequencing was used to evaluate safety-and functionality-related genetic traits. The protective effect of P. acidilactici 46A was investigated in a dextran sulphate sodium (DSS)-induced murine model of colitis, including histological evaluation, inflammatory marker analysis, and gut microbiota profiling. Results: P. acidilactici 46A showed high survival under simulated gastrointestinal conditions and bile exposure, antimicrobial activity against Gram-positive and Gram-negative bacteria and yeasts, and strong adhesion to HT-29 cells compared with other tested strains. Genomic analysis confirmed the absence of virulence factors and clinically relevant antibiotic resistance genes. In DSS-treated mice, oral administration of P. acidilactici 46A significantly reduced colitis severity, preserved colonic mucosal architecture, and decreased inflammatory markers, including IL-1β and IL-6. Conclusion: Pediococcus acidilactici 46A is a safe and functionally active probiotic candidate that attenuates intestinal inflammation and preserves mucosal integrity in a murine model of colitis, supporting its potential application in the prevention or adjunctive treatment of inflammatory gut disorders.