Short communication Competitive exclusion of enteropathogens from human intestinal mucus by Bifidobacterium strains with acquired resistance to bile — A preliminary study Miguel Gueimonde a,b,c, ⁎ , Abelardo Margolles c , Clara G. de los Reyes-Gavilán c , Seppo Salminen a,b a Functional Foods Forum, University of Turku, Turku, Finland b Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland c Instituto de Productos Lácteos de Asturias, CSIC, Villaviciosa, Asturias, Spain Received 11 September 2005; received in revised form 6 April 2006; accepted 14 May 2006 Abstract The ability to inhibit the adhesion and to displace selected pathogens from human intestinal mucus of two Bifidobacterium strains with acquired resistance to bile, were assessed and compared with those of their bile sensitive original strains. A preliminary characterization of the macromolecules involved in the adhesion was also carried out. The inhibition of adhesion and the displacement of enteropathogens previously adhered were found to be specific, depending on the strains used. The cholate-resistant strain Bifidobacterium bifidum M6dCo, that adhered more to mucus than its original, was able to inhibit the adhesion and to displace pathogens from mucus significantly more than its original cholate- sensitive strain B. bifidum M6. Contrary to this, two strains showing similar adhesion levels, B. bifidum A1 and its bile resistant derivative B. bifidum A1dOx, did not display any differences. Different molecules appear to be involved in the adhesion of the strains B. bifidum M6 and B. bifidum M6dCo. These differences in the cellular surface may explain the differences in competitive exclusion observed between both strains. © 2006 Elsevier B.V. All rights reserved. Keywords: Bifidobacterium; Enteropathogens; Probiotics; Adhesion; Bile resistance 1. Introduction Selected strains of bifidobacteria are increasingly being introduced as probiotics in functional food products. To exert beneficial effects and persist in the intestinal tract these bacteria must overcome biological barriers, including acid in the stomach and bile in the intestine (Lankaputhra and Shah, 1995). Among the criteria suggested for the selection of probiotics the ability to adhere to the gastrointestinal mucosa is frequently considered (Collins et al., 1998; Salminen et al., 1998; Ouwehand et al., 2002a). This property is important for colonization (Crociani et al., 1995), modulation of the immune system (Schiffrin et al., 1997) and it has been recently related to certain beneficial effects of probiotics (Castagliuolo et al., 2005). Although the bile-tolerance mechanisms of bifidobacteria are poorly understood, strains expressing increased resistance to bile have been obtained by adaptation to gradually increasing concentrations of these compounds (Margolles et al., 2003; Noriega et al., 2004). The acquisition of resistance to one bile salt also conferred cross-resistance to others, increased resis- tance to low pH and induced stable changes in carbohydrate fermentation profiles and some glycosidase activities (Mar- golles et al., 2003; Noriega et al., 2004). It has been also shown that this acquisition induces changes in membrane protein profiles (Margolles et al., 2003) and in the ability to adhere to human intestinal mucus (Gueimonde et al., 2005). Therefore, it is reasonable to hypothesize that highly adhesive bile-salt resis- tant derivative strains would have also acquired an enhanced International Journal of Food Microbiology 113 (2007) 228 – 232 www.elsevier.com/locate/ijfoodmicro ⁎ Corresponding author. Current address: Instituto de Productos Lacteos de Asturias, Consejo Superior de Investigaciones Científicas, Carretera de Infiesto s/n. 33300 Villaviciosa, Asturias, Spain. Tel.: +34 985892131; fax: +34 985892233. E-mail addresses: mgueimonde@ipla.csic.es, miguel.gueimonde@utu.fi (M. Gueimonde). 0168-1605/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2006.05.017