Antibiofilm activity of Limosilactobacillus fermentum SH2 and Lactococcus lactis extracts against strains of methicillin-resistant Staphylococcus aureus, Staphylococcus hominis SH7, and Pseudomonas aeruginosa.

BACKGROUND

Lactobacillus species are commonly studied probiotic organisms that can inhibit pathogenic bacteria through many mechanisms for the bacterial cells themselves or their extracts, both in vitro and in vivo.

METHODS AND

RESULTS

The inhibitory effects of two lactobacilli species (Limosilactobacillus fermentum SH2 (LF) and Lactococcus lactis subsp. Lactis NRRL1821 (LL)) on the formation of biofilms of methicillin-resistant Staphylococcus aureus ATCC 43,300, Staphylococcus hominis SH7 OM489438, and Pseudomonas aeruginosa ATCC 35,032 were investigated. Molecular analysis of the pathogenic strains revealed that the seb gene is exclusively detected in S. aureus, whereas the icaAA and icaD genes were detected in both S. aureus and S. hominis SH7. Multiple virulence genes, including pslA, pelA, toxA, exoT, exoU, lasB, lasR, and rhlR, were detected in P. aeruginosa. The inhibition of staphylococcal biofilms by Limosilactobacillus fermentum SH2 was distinct, reaching 97.81% inhibition against MRSA, whereas Lactococcus lactis activity increased against P. aeruginosa, with inhibition reaching 98.95%. The results of confocal laser scanning microscopy using acridine orange‒propidium iodide staining demonstrated biofilm disruption and damage to the bacterial membrane. Reverse transcriptase-quantitative polymerase chain reaction analysis demonstrated significant downregulation of the expression of biofilm- and quorum-sensing genes (icaA, icaD, lasR, and rhlR).

CONCLUSIONS

These results clearly demonstrated that LAB extracts have antibiofilm activity through membrane disruption, inhibition of the quorum-sensing network, and suppression of genes involved in biofilm formation. These extracts can be developed as alternative strategies for controlling MDR pathogenic bacteria and biofilm-associated infections, as well as reducing the dependence on trivial drugs.