In Vitro Effects of <i>Lactobacillus plantarum</i> LN66 and Antibiotics Used Alone or in Combination on <i>Helicobacter pylori</i> Mature Biofilm

<i>Helicobacter pylori</i> is a gastrointestinal pathogen with high prevalence that harms human health. Studies have shown that <i>H. pylori</i> can form antibiotic-tolerant biofilms, which may interfere with the efficacy of clinical antibiotic therapy. Probiotics can antagonize planktonic and biofilm pathogen cells and thus may play an auxiliary role in <i>H. pylori</i> antibiotic therapy. However, the effects of different probiotic strains and antibiotic combinations on <i>H. pylori</i> biofilms need to be further investigated. We determined the cell viability of <i>H. pylori</i> mature biofilms after treatment with <i>Lactobacillus plantarum</i> LN66 cell-free supernatant (CFS), clarithromycin (CLR), and levofloxacin (LVX) alone or in combination by the XTT method. Biofilm cells were observed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Subsequently, protein and polysaccharide concentrations in biofilm extracellular polymeric substances (EPSs) were quantitatively detected by the Bradford method and the phenol-sulfate method. The results showed that LN66 CFS had an eradication effect on mature <i>H. pylori</i> biofilm. When used in combination with CLR, LN66 CFS significantly attenuated the eradication effect of CLR on biofilms; in contrast, when used in combination with LVX, LN66 CFS enhanced the disrupting effect of LVX. We speculate that the different effects of CFS and antibiotic combinations on biofilms may be related to changes in the content of proteins and polysaccharides in EPS and that the combination of CFS and CLR might promote the secretion of EPS, while the combination of CFS and LVX might have the opposite effect. Accordingly, we suggest that supplementation with <i>L. plantarum</i> LN66 may provide additional help when therapy involving LVX is used for clinical <i>H. pylori</i> biofilm eradication, whereas it may impair CLR efficacy when therapy involving CLR is used.