Transmissionofthegutmicrobiota:spreadingofhealthHilaryP.Browne1,B.AnneNeville1,SamuelC.Forster1,2,3,andTrevorD.Lawley11Host–MicrobiotaInteractionsLaboratory,WellcomeTrustSangerInstitute,Hinxton,CambridgeshireCB101SA,UK2CentreforInnateImmunityandInfectiousDiseases,HudsonInstituteofMedicalResearch,Clayton,Victoria3168,Australia3DepartmentofMolecularandTranslationalSciences,MonashUniversity,Clayton,Victoria3800,AustraliaAbstractTransmissionofcommensalintestinalbacteriabetweenhumanscouldpromotehealthbyestablishing,maintainingandreplenishingmicrobialdiversityinthemicrobiotaofanindividual.Unlikepathogens,theroutesoftransmissionforcommensalbacteriaremainunappreciatedandpoorlyunderstood,despitethelikelycommonalitiesbetweenboth.Consequently,broadinfectioncontrolmeasuresthataredesignedtopreventpathogentransmissionandinfection,suchasoversanitationandtheoveruseofantibiotics,mayinadvertentlyaffecthumanhealthbyalteringnormalcommensaltransmission.InthisReview,wediscussthemechanismsandfactorsthatinfluencehost-to-hosttransmissionoftheintestinalmicrobiotaandexaminehowabetterunderstandingoftheseprocesseswillidentifynewapproachestonurtureandrestoretransmissionroutesthatareusedbybeneficialbacteria.Thehumanintestinalmicrobiotaisoneofthemostdenselypopulatedmicrobialcommunitiesknowntoexist1.Thiscommunityhasimportantmetabolicandprotectiverolesinhumanhealththroughmetabolizingindigestiblecarbohydrates,producingvitamins,preventinginfectionbypathogenicbacteriaandmodulatinghostimmuneresponses2.Bacteriaformthemajorityofthemicrobialbiomassinthehumangastrointestinalmicrobiotaandtheycarryoutthemajorityofthemetabolicactivities2,3.Mostofthebacteriainthegastrointestinaltractresideinthelargeintestine,withtherestfoundprimarilyinthesmallintestineandstomach4.Themajorityofthesebacteriabelongtotwomainphyla—theBacteroidetesandFirmicutes.Thesephyla,togetherwiththeProteobacteria,Actinobacteria,SynergistetesandFusobacteria,containalmostallofthebacterialspeciesfoundinthehumangastrointestinaltract5–7.Mostoft...
