Paenibacillus polymyxa is a Gram-positive, endospore-forming bacterium known for its ability to produce a variety of antimicrobial compounds, such as polymyxins, fusaricidins, and other lipopeptides. The use of P. polymyxa to support or treat bacterial infections is rooted in its demonstrated antibacterial activity in laboratory and animal studies. Multiple in vitro studies have shown that P. polymyxa can inhibit the growth of several pathogenic bacteria, including Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, largely due to the secretion of non-ribosomal peptides with bactericidal properties.

Clinical use in humans is limited, but the bacterium's derivatives (notably polymyxin antibiotics, such as polymyxin B and colistin, originally sourced from P. polymyxa) have been used for decades to treat multidrug-resistant Gram-negative bacterial infections. These antibiotics are FDA-approved for certain severe infections. However, the direct use of the live bacterium or its unrefined extracts as a treatment for infection in humans is not standard medical practice, and there is little clinical trial data supporting safety or efficacy in this context.

Overall, while there is substantial scientific evidence at the preclinical level for the antibacterial properties of P. polymyxa and its metabolites, translation to direct clinical use is limited. Thus, the evidence supporting P. polymyxa for treating bacterial infections rates as moderate.