lecture 8 probiotic bacteria：讲座8益生菌

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1、LectureOutlineIntroduction/DefinitionofProbioticsFundamentalQuestionsRecentFindingsPossibleModesofActionRationaleforSelectingProbioticsConclusionsandFurtherDirectionsSourceofnotes:Verschuere,L.,Rombaut,G.,Sorgeloos,P.,andVerstraete,W.,2000.Probioticbacteriaasbiologicalc

2、ontrolagentsinaquaculture.Microb.Mol.Biol.Rev.,64(4):655-671.IntroductionAsweknow,aquacultureisgrowingfasterthanbeefcattleproduction(10%vs.3%)Epizootics(disease)=majorlimitingfactorinfish/shrimpdevelopments!Disinfectants,antimicrobialdrugshavehadlittleeffectincontrollin

3、gdisease.MassiveuseofantimicrobialsincreasesselectivepressureonmicrobesandencouragesnaturalemergenceofbacterialresistanceResistantbacteriathriveafternon-resistantstrainshavebeenkilledandcanevenpassonresistancegenestootherbacteriathathavenotbeenexposedtoantibioticsIntrod

4、uctionEmphasisshouldbeplaceonpreventionMorecost-effectivethancure!Antimicrobials,disinfectantsandpesticideslargelytreatsymptomsoftheproblemandnotthecauseAlternativestrategiesarejustcatchingonExample:viavaccination,Norwayhasreducedchemicaltherapeutantusefrom50MTin1987tol

5、essthan747kgin1997(with7xconcomitantproductionincrease!)Other:useofimmunostimulantsw/orw/outvaccinesIntroductionUseofbacteriaasafoodsourceandasabiologicalcontrolagentoffishdiseasewasfirstproposedbyYasudaandTaga(1980)Vibrioalginolyticushasbeenusedasaprobioticinshrimphatc

6、heriesinEcuadorsince1992Reducedhatcherydowntimefrom7dayspermonthtolessthan21daysperyear!FAOhasnowdesignateduseofprobioticsasamajormeansforimprovementofaquaticenvironmentalqualityUltimategoal:makeaquacultureproductsmoreacceptabletoconsumersDefinitionofProbioticsManypropo

7、sed,however:alivemicrobialfeedsupplementwhichbeneficiallyaffectsthehostanimalbyimprovingitsintestinalbalanceHistorically:terrestrialanimals,genusLactobacillusDefinition(above)requiressomeadditionalconsiderations:1)bacteriainaquaticmediuminfluencecompositionofgutmicrobio

8、taandviceversa2)immediateambientenvironmenthasmuchgreaterinfluenceonmicrobiotathanwithterrestrialsInaquaticenv