Antibiofilm Activity of Kefir Probiotic Lactobacilli Against Uropathogenic Escherichia coli (UPEC)

Background: Inhibition of biofilm formation is essential for the prevention and treatment of urinary tract infection. This study was aimed to identify the probiotic potential of Lactobacillus strains isolated from kefir and evaluate their antimicrobial and antibiofilm activities against Uropathogenic Escherichia coli (UPEC).

Methods: Twelve Lactobacillus strains were evaluated. Antimicrobial and antibiofilm activities of Cell Free Supernatant (CFS) of the Lactobacillus strains against UPEC isolates were evaluated by agar well diffusion method and crystal violet assay, respectively. Probiotic potential of selected isolates was assessed by analyzing their tolerance to acidic pH and bile salts, auto-aggregation ability, co-aggregation with Escherichia coli (E. coli) and hemolytic activity. The isolates were identified by phenotypic and 16S rRNA gene sequencing.

Results: The CFS of all lactobacilli strains was able to inhibit UPEC isolates even after neutralization. Four out of 12 isolates inhibited the biofilm formation by UPEC in the range 62-75%. The viability under acidic condition varied among the isolates ranging from 6-89.8%. All the isolates could tolerate the 0.3% bile and eight isolates showed the adaptation time of less than 1 hr. All the strains exhibited co-aggregation with E. coli. Auto-aggregation was highly correlated with co-aggregation of all lactobacilli strains with E. coli (r=0.889, p<0.001). The isolates with satisfactory probiotic potential and higher ability of biofilm inhibition and antibacterial activity belonged to the species Lactobacillus rhamnosus and Lactobacillus paracasei.

Conclusion: All four selected probiotic strains exhibited antimicrobial and antibiofilm activities, which suggest potential applications for controlling or preventing infections caused by UPEC.