A Survey of Multiple Candidate Probiotic Bacteria Reveals Specificity in the Ability to modify the effects of Key Wound Pathogens

We have evaluated the inhibitory effects of supernatants and lysates derived from several candidate probiotics, on the growth and biofilm formation of wound pathogens, and their ability to protect human primary epidermal keratinocytes from the toxic effects of pathogens. Supernatants (neutralised and non neutralised) and lysates (via sonication) from Lactiplantibacillus plantarum, Limosilactobacillus reuteri, Bifidobacterium longum, Lacticaseibacillus rhamnosus GG and Escherichia coli Nissle 1917 were tested for their inhibitory effects against Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumanni. The supernatants of L. plantarum, L. rhamnosus, B. longum and L. rhamnosus GG reduced the growth of S. aureus, E. coli and A. baumanni. B. longum additionally inhibited P. aeruginosa growth. However, neutralised Lactobacillus supernatants did not inhibit growth and in some cases were stimulatory. Lysates of L. plantarum and L. reuteri inhibited S. pyogenes while B. longum lysates inhibited E. coli and S. aureus growth. E. coli Nissle 1917 lysates enhanced the growth of S. pyogenes and P. aeruginosa. Biofilm formation by E. coli was reduced by lysates of L. reuteri and neutralised supernatants of all candidate probiotics. P. aeruginosa biofilm formation was reduced by E.coli Nissle supernatant, but increased by L. plantarum, L. reuteri and Bifidobacterium longum lysates. L. reuteri decreased the toxic effects of S. aureus on keratinocytes whilst E. coli Nisslen1917 lysates protected keratinocytes from S. pyogenes-toxicity. In conclusion, lactobacilli and E. coli Nissle lysates confer inhibitory effects on pathogenic growth independently of acidification, and may beneficially alter the outcome of interactions between host cell pathogen in a species-specific manner.