Lactic acid bacterial symbionts from the honeybee: Characteristics and applications in wound management

Sammanfattning: Antibiotic resistance is now a large threat with worldwide agreement that we will fall into a post-antibiotic era unless there is suitable treatment alternatives discovered. In recent years, chronic wounds have become a major burden on society and treatment is complicated. Honey has been widely used as a topical treatment for wounds yet there is much discourse between studies examining its effect and still some of its antimicrobial effect has not been characterized. In this thesis we investigate some characteristics of 13 novel Lactic acid bacterial (LAB) symbionts originating from the honey stomach of the western honeybee. The LABs involvement in honey production and their antimicrobial action against many environmental bacteria and yeasts hypothesizes that these LAB symbionts may be a good alternative to antibiotics for the topical treatment of chronic wounds. First we investigated the effect of stress on the extracellular protein production of all 13 LAB separately. We revealed that this extracellular production varied between species and genera, and that different microbial stressors had varying effects. These putative proteins may have links with the LAB survival in their niche possibly in attachment or as antimicrobials. Secondly, we investigated some characteristics of the LAB and discovered a link between the therapeutic effect of honey and these symbionts. We identified a myriad of bioactive substances that the LAB produce and had broad-spectrum antimicrobial activity against human pathogens including antibiotic resistant species. The effect varied between species, but all 13 LAB combined were the most effective. Finally we investigated the antimicrobial effect the LAB symbionts had together in a standardized concentration with heather honey, in vitro against human and animal pathogens, and in vivo in two pilot studies. We showed once again the LAB formulation had broad-spectrum activity when combined. When applied to chronic wounds on horses and finally on humans, we saw in both cases remarkable results towards wound healing. Bacterial diversity was also investigated and we observed that the wounds were polymicrobial in nature and bacterial diversity varied between subjects, but there were a number of genera that are readily identified throughout the majority of samples. This thesis studies the hypothesis of a novel LAB microbiota as an alternative tool in wound management and provides knowledge about these symbionts’ therapeutic and antimicrobial characteristics in vitro and in vivo. It contributes to an understanding of how interdisciplinary research can proceed starting from basic knowledge to medical applications. In conclusion, further work, including more in vitro experiments and controlled clinical trials, could in a future perspective establish these LAB symbionts as an alternative to antibiotics in wound treatment, and possibly other infections.