The double-edged sword of interspecies competition in antimicrobial applications

Korte inhoud:Bacteria are social organisms that live within ecologically complex multispecies communities. Within these communities, bacteria engage in a wide array of interactions with the diverse species that surround them, ranging from cooperation to competition. These interspecies social interactions not only shape the ecological role of individual bacteria, but can also impact community structure, dynamics, function and tolerance towards antimicrobials. Interspecies social interactions, therefore, exert a significant influence on various applications. On the one hand, the competitive mechanisms of microbial isolates can serve as a valuable tool, for example to combat antibiotic-resistant pathogens. On the other hand, competition can be seen as a burden, as it has been shown to increase the tolerance of multispecies biofilm communities to eradication methods. In this thesis, we aimed to elucidate the effects of interspecies competition on the intricate dynamics of multispecies communities and how this, in turn, impacts the development and efficacy of several antimicrobial applications. (i) As a first application, we focused on the use of the natural arms race between indigenous microbiota and enteropathogens as an alternative control method against Salmonella in the poultry industry. We identified and verified a mixed-species probiotic cocktail that strongly inhibited the growth of Salmonella based on predictions by simple generalized Lotka-Volterra models. In addition, we also studied the downside of working with potent competitive isolates by evaluating the impact of their competition on the induction of defensive responses in Salmonella, focusing on biofilm formation and epithelial invasion. (ii) The second antimicrobial application in which we studied the importance of interspecies social interactions was the combinatorial therapy of probiotics and antibiotics. We showed that in a toxic environment, i.e. in the presence of antibiotics, probiotic competition can be suppressed and coexistence enhanced when the dominant competitor relies on the weaker one for protection, thereby compromising the efficacy of probiotic applications. However, the stability of both intra- and interspecies communities, with either unilateral or bilateral cross-protection, was highly condition dependent. (iii) The final application studied in this thesis revolved around the increased tolerance of multispecies biofilms, partially caused by competition, against cleaning and disinfection protocols in beer breweries. One of the most promising alternatives to the ineffective cleaning protocols is the prevention of biofilm formation. Therefore, we benchmarked the efficacy of 21 biofilm inhibitors, including three 2-aminoimidazoles, against multiple relevant biofilm model communities. In summary, this thesis underscores the importance of interspecies interactions within the context of antimicrobial applications. Interspecies competition can serve as a valuable tool for innovative approaches, yet it can also complicate the eradication of undesirable species.

Jaar van publicatie:2024

Toegankelijkheid:Closed