title: Lactobacillus rhamnosus GG Outcompetes Enterococcus faecium via Mucus-Binding Pili: Evidence for a Novel and Heterospecific Probiotic Mechanism.
abstract: Vancomycin-resistant enterococci (VRE) have become a major nosocomial threat. Enterococcus faecium is of special concern, as it can easily acquire new antibiotic resistances and is an excellent colonizer of the human intestinal tract. Several clinical studies have explored the potential use of beneficial bacteria to weed out opportunistic pathogens. Specifically, the widely studied Lactobacillus rhamnosus strain GG has been applied successfully in the context of VRE infections. Here, we provide new insight into the molecular mechanism underlying the effects of this model probiotic on VRE decolonization. Both clinical VRE isolates and L. rhamnosus GG express pili on their cell walls, which are the key modulators of their highly efficient colonization of the intestinal mucosa. We found that one of the VRE pilus clusters shares considerable sequence similarity with the SpaCBA-SrtC1 pilus cluster of L. rhamnosus GG. Remarkable immunological and functional similarities were discovered between the mucus-binding pili of L. rhamnosus GG and those of the clinical E. faecium strain E1165, which was characterized at the genome level. Moreover, E. faecium strain E1165 bound efficiently to mucus, which may be prevented by the presence of the mucus-binding SpaC protein or antibodies against L. rhamnosus GG or SpaC. These results present experimental support for a novel probiotic mechanism, in which the mucus-binding pili of L. rhamnosus GG prevent the binding of a potential pathogen to the host. Hence, we provide a molecular basis for the further exploitation of L. rhamnosus GG and its pilins for prophylaxis and treatment of VRE infections.
  
  
  
  Concern about vancomycin-resistant Enterococcus faecium causing nosocomial infections is rising globally. The arsenal of antibiotic strategies to treat these infections is nearly exhausted, and hence, new treatment strategies are urgently needed. Here, we provide molecular evidence to underpin reports of the successful clinical application of Lactobacillus rhamnosus GG in VRE decolonization strategies. Our results provide support for a new molecular mechanism, in which probiotics can perform competitive exclusion and possibly immune interaction. Moreover, we spur further exploration of the potential of intact L. rhamnosus GG and purified SpaC pilin as prophylactic and curative agents of the VRE carrier state.
authors.affiliation: Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands hanne.tytgat@wur.nl.
authors.forename: Hanne L P
authors.identifier: 0000-0001-6270-2110
authors.initials: HL
authors.lastname: Tytgat
authors.affiliation: Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.
authors.forename: François P
authors.initials: FP
authors.lastname: Douillard
authors.affiliation: Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.
authors.forename: Justus
authors.initials: J
authors.lastname: Reunanen
authors.affiliation: Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.
authors.forename: Pia
authors.initials: P
authors.lastname: Rasinkangas
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Antoni P A
authors.initials: AP
authors.lastname: Hendrickx
authors.affiliation: Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
authors.forename: Pia K
authors.initials: PK
authors.lastname: Laine
authors.affiliation: Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
authors.forename: Lars
authors.initials: L
authors.lastname: Paulin
authors.affiliation: Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland RPU Immunobiology, Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Reetta
authors.initials: R
authors.lastname: Satokari
authors.affiliation: Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland RPU Immunobiology, Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Helsinki, Finland.
authors.forename: Willem M
authors.initials: WM
authors.lastname: de Vos
mesh_terms: D016984:Enterococcus faecium / Q000502:physiology*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D006801:Humans; D052201:Lacticaseibacillus rhamnosus / Q000502:physiology*; D056265:Microbial Interactions; D009093:Mucus / Q000382:microbiology*; D019936:Probiotics / Q000378:metabolism*