Inhibition of <i>Streptococcus pyogenes</i> biofilm by <i>Lactiplantibacillus plantarum</i> and <i>Lacticaseibacillus rhamnosus</i>

The human pathobiont <i>Streptococcus pyogenes</i> forms biofilms and causes infections, such as pharyngotonsillitis and necrotizing fasciitis. Bacterial biofilms are more resilient to antibiotic treatment, and new therapeutic strategies are needed to control biofilm-associated infections, such as recurrent pharyngotonsillitis. <i>Lactiplantibacillus plantarum</i> and <i>Lacticaseibacillus rhamnosus</i> are two bacterial commensals used for their probiotic properties. This study aimed to elucidate the anti-biofilm properties of <i>L. plantarum</i> and <i>L. rhamnosus</i> cell-free supernatants (LPSN and LRSN, respectively) on <i>S. pyogenes</i> biofilms grown <i>in vitro</i> in supplemented minimal medium. When planktonic or biofilm <i>S. pyogenes</i> were exposed to LPSN or LRSN<i>, S. pyogenes</i> survival was reduced significantly in a concentration-dependent manner, and the effect was more pronounced on preformed biofilms. Enzymatic digestion of LPSN and LRSN suggested that glycolipid compounds might cause the antimicrobial effect. In conclusion, this study indicates that <i>L. plantarum</i> and <i>L. rhamnosus</i> produce glycolipid bioactive compounds that reduce the viability of <i>S. pyogenes</i> in planktonic and biofilm cultures.IMPORTANCE<i>Streptococcus pyogenes</i> infections are a significant concern for populations at risk, such as children and the elderly, as non-invasive conditions such as impetigo and strep throat can lead to severe invasive diseases such as necrotizing fasciitis. Despite its susceptibility to current antibiotics, the formation of biofilm by this pathogen decreases the efficacy of antibiotic treatment alone. The ability of commensal lactobacillus to kill <i>S. pyogenes</i> has been documented by previous studies using <i>in vitro</i> settings. The relevance of our study is in using a physiological setup and a more detailed understanding of the nature of the lactobacillus molecule affecting the viability of <i>S. pyogenes</i>. This additional knowledge will help for a better comprehension of the molecules' characteristics and kinetics, which in turn will facilitate new avenues of research for its translation to new therapies.