Study of the In Vitro Antagonistic Activity of Various Single-Strain and Multi-Strain Probiotics against Escherichia coli

Abstract

<i>Escherichia coli</i> is an important commensal of our gut, however, many pathogenic strains exist, causing various severe infections in the gut or beyond. Due to several antibiotic resistance patterns of <i>E. coli</i>, research of alternative treatments or adjuvant therapy is important. One of these is the use of probiotics as antagonistic agents against <i>E. coli</i>. Most published studies investigate only one strain of <i>E. coli</i> and single-strain probiotics. The objectives of this study were to evaluate the antagonistic activity of selected single-strain and multi-strain probiotic supplements against selected clinical <i>E. coli</i> pathotypes using the in vitro agar spot test and the co-culturing method. Molecular methods were used to determine the presence of the genus lactobacilli and bifidobacteria as well as certain selected strains in the probiotic supplements. The agar-spot test showed that the multi-strain probiotics were more effective than the single-strain probiotics. On the other hand, the co-culturing method showed the opposite result, indicating that results are importantly influenced by the chosen method. The most effective single-strain probiotics against <i>E. coli</i> strains were <i>Bifidobacterium animalis</i> subsp. <i>lactis</i> BB-12 and <i>Lactobacillus reuteri</i> DSM 17938. The most effective multi-strain probiotics contained lactobacilli, bifidobacteria and enterococci strains, thus proving that most effective probiotics against <i>E. coli</i> strains are the lactic acid bacteria and bifidobacteria. The overall results from both in vitro tests reveal that all selected probiotics exhibited an antagonistic activity against all <i>E. coli</i> strains. From a public health perspective probiotics have thus proved to be successful in inhibiting the growth of <i>E. coli</i> and could therefore be used as adjuvant therapy or alternative therapy in <i>E. coli</i> infections.