Evaluation of the Simultaneous Effects of Lactobacillus delbrueckii and L. lactis on Biofilms of Isolates from Chronic Ulcer Infections with Multiple-drug Resistance

Background: Bacterial biofilm is a major barrier to chronic wound healing. Therefore, the prevention of biofilm formation has an effective role in accelerating the healing of these wounds. Today, probiotics’ anti-biofilm and antibacterial activity have been proven, and bacteriotherapy by probiotics is a new strategy for treating chronic ulcer infections. Objectives: The present study aimed to investigate the synergistic effects of Lactobacillus delbrueckii and L. lactis on biofilms of bacterial agents isolated from these ulcers in the human plasma biofilm model (hpBIOM). Methods: This study examined 82 specimens of chronic ulcer biofilms and identified bacterial isolates using phenotypic and molecular methods. After preparing the hpBIOM, 50 µL of each probiotic (109 CFU/mL) was added in two doses separately and simultane-ously. After 24 hours, 1 mL of bromelain (0.1 g/mL) was added to the complex and incubated at 37°C for two hours. Then, the surviving bacterial cells were counted by serial dilutions. Results: Among 119 bacterial isolates, Staphylococcus aureus (19%), Escherichia coli (17.0%), and Pseudomonas aeruginosa (14%) were the most common bacterial isolates. Lactobacillus delbrueckii showed anti-biofilm activity against multiple-drug resistance pathogens, Staphylococcus, P. aeruginosa, and K. pneumoniae. Although L. lactis had anti-biofilm activity against these three pathogens, its effect was less than that of L. delbrueckii. The two probiotics did not have any synergistic effect on the biofilms of the isolates. Conclusions: The results of the present study emphasized the potential of probiotics in destroying biofilms of isolates with multiple-drug resistance; however, their simultaneous use for this purpose requires further investigation