Resistance of Bifidobacteria Toward Antibiotics.

The genus Bifidobacterium constitutes one of the main groups of the human microbiota and some species have a long history of safe consumption supporting an excellent safety record. However, in the context of the increasing worldwide problems associate to the rise of pathogenic microorganisms with acquired resistance to antibiotics, the risk associated to the presence of antibiotic resistance determinants should always be a key starting point for the introduction of any microbial strain into the food chain. Bifidobacteria are not an exception and the presence of resistance to antibiotics is of interest since these microorganisms could potentially act as a reservoir of such resistances. In this context it is necessary to evaluate the presence of antibiotic resistance in any bifidobacterial strain to be included into the food chain. To this end, the first step is the determination of the antibiotic resistance pattern of the strain and the comparison with the susceptibility breakpoints for that species, allowing identifying the presence of atypical resistances in the strain. In this chapter we discuss the many efforts done to harmonize the methods used for the evaluation of antimicrobial susceptibility in the genus Bifidobacterium and the currently available guidelines. Moreover, we describe, in detail, the reference protocols used for evaluating the in vitro antimicrobial activity on bifidobacteria.