Paenibacillus polymyxa is a soil-dwelling bacterium recognized for its production of a variety of bioactive compounds, including antibiotics and antimicrobial peptides (such as polymyxins and fusaricidins). In agricultural and veterinary contexts, it has been explored as a probiotic and as an alternative to traditional antibiotics for promoting plant and animal health. The scientific justification for its use as an antibiotic alternative is based on its demonstrated ability to inhibit a broad spectrum of pathogenic bacteria and fungi, both in vitro and in some in vivo models.

Multiple peer-reviewed studies have shown that P. polymyxa can suppress plant pathogens and enhance plant growth, largely through the secretion of antimicrobial substances. In animal studies, particularly in poultry and aquaculture, supplementation with P. polymyxa strains has been reported to improve growth performance and modulate gut microbiota, resulting in reduced pathogen loads. However, while the mechanistic basis and some efficacy data are established, human clinical trials are lacking, and most evidence comes from laboratory or field studies in plants and non-human animals.

Therefore, while there is scientific evidence supporting P. polymyxa as an alternative to antibiotics, especially in agriculture and animal husbandry, the overall strength of evidence for its use in humans is moderate (rated 3/5), pending further clinical research.