Exploring the Antagonistic Polymicrobial Interaction of Alcaligenes faecalis with Prokaryotic and Eukaryotic Microorganisms

Alcaligenes faecalis, a generally nonpathogenic, Gram-negative bacterium, has been observed by our laboratory to possess antagonistic activity against antimicrobial-resistant genera Staphylococcus, Candida, and Bacillus. This study focused on exploring the inhibition mechanism of A. faecalis against the three genera, with an emphasis on S. aureus. A library of A. faecalis transposon mutants was constructed and identified fourteen possible genetic factors linked to this inhibitory activity. Characterization of this inhibition indicated that A. faecalis suppressed S. aureus planktonic and biofilm growth via a contact-dependent mechanism, with pronounced effects during biofilm attachment phase. In a Caenorhabditis elegans model, A. faecalis reduced S. aureus microbial burden, suggesting efficacy in vivo. Taken collectively, these results indicate a unique polymicrobial interaction of A. faecalis with both Gram-positive bacteria and eukaryotic cells and could prove to be a potential use of Alcaligenes in combating antimicrobial resistance as it has become a major threat to global health.