Group 1: Microbes that affect our body weight

Howdosmallthingsmakeabigdifference? August2014Lesson5:Howdomicrobesinteractwithhumans?

Group1:Microbesthataffectourbodyweight

Ifmicrobesworkinourguttodecomposeourfoodandprovideusnutrients,isitpossiblethattheycouldbeproviding“toomuch”ofagoodthing?RuchiMathurandhercolleagueshaverecentlypublishedastudyillustratingthatthenumberofcertaintypesofmicrobesinoverweightpeoplearedifferentfromthosepeopleofanormalbodyweight.Theyfocusedontwomicrobesthatareabundantinthegut:thearchaeaM.smithiiandthebacteriaBacteroidetes.M.smithiiisananaerobic(notrequiringoxygen)microbethatuseshydrogenandproducesmethane.ItobtainshydrogenfromBacteroidetes,whichproduceshydrogenasanendproductofmetabolism.M.smithiiremovestheexcesshydrogenfromBacteroidetes’environment.ThishydrogenremovalpromotesthepopulationofBacteroidetesintheguttoincreasewhichleadstoanincreaseinhydrogenproduction.HydrogenhelpsM.smithiibreakdownthecomplexsugarsweconsumeandturnsthemintoshortchainfattyacids(SCFAs),whichwecanthenuseasasourceofenergy(extracalories).Bacteroidetesalsoprovidesthehumangutwithvitaminsandnutrients,whilethehumangutprovidesnutrients(intheformoffoodthatweconsume)andaplacetoliveforbothBacteroidetesandM.smithii.Thus,thebacteria,archaea,andhumanhostallrelyoneachotherinmutualisticrelationshipstosurviveandthriveinthegutecosystem.Thefollowingdiagramsummarizestherelationshipsbetweenthesethreeorganisms.


Inthisstudy,Mathurandhercolleaguesanalyzedthemethaneandhydrogencontentofvarioussubjects’breath.GraphsAandBrepresenttheresultsofMathur’sstudy.Forbothgraphs,therewerefourgroupsofsubjects:1)Normal,2)HydrogenOnly,3)MethaneOnly,4)MethaneandHydrogen.Subjectsinthe“normal”grouphadanormalamountofhydrogen,20ppm(partspermillion)orless,andanormalamountofmethane,3ppmorless.(“Normal”levelswerebasedonpreviousresearch.)Ifsubjectshadgreateramountsthanthenormalamountofhydrogen(≥20ppm)detectedbuthadlessthanthenormalamountofmethane(≤3ppm),theywereconsideredhydrogenpositive(representedbythe“HydrogenOnly”bar),while≥3ppmofmethanedetectedbut≤20ppmofhydrogenwasconsideredmethanepositive(representedbythe“MethaneOnly”bar).Ifsubjectshadgreaterthanthenormalamountsofbothgases(≥20ppmofhydrogenand≥3ppm),theywereconsideredhydrogenandmethanepositive(representedbythe“MethaneandHydrogen”bar).References:

Buck,S.S.andGordon,J.I.(2006).Ahumanizedgnotobioticmousemodelofhost-archael-bacterial mutualism.PNAS.103(26):10011-10016.

Mathur,R.,Amichai,M.,Chua,K.S.,Mirocha,J.,Barlow,G.M.,andPimentel,M.(2013).Methaneand hydrogenpositivityonbreathtestisassociatedwithgreaterbodymassindexandbodyfat.JClin EndocrinolMetab.98(4):E698-E702.

FiguretakenfromMathuretal.,2013,p.E700


ExpertGroupStudentSheet

Group1:Microbesthataffectourbodyweight

1.Accordingtothearticle,howdoM.smithii,Bacteroides,andthehumangutworktogethertoformmutualisticrelationships?

2.WhattypeofinformationisprovidedingraphsAandB?

3.AccordingtotheNationalInstitutesofHealth,ahealthybodymassindex(BMI)is18.5-24.9.IngraphA,whatdoyounoticeabouttheamountsofhydrogenandmethaneinsubjectswithhealthyBMIscomparedtosubjectswhowereoverweight?


4.AccordingtotheAmericanCouncilofExercise,overweightpeoplehave,onaverage,greaterthan30%bodyfat.IngraphB,whatdoyounoticeabouttheamountsofhydrogenandmethaneinsubjectswithhealthybodyfatpercentagecomparedtosubjectswhowereoverweight?

5.BasedongraphsAandB,whatistherelationshipbetweenbodyweightandtheamountofmethaneandhydrogencontentinone’sgut?

5b.DuetotheknownmutualisticrelationshipsbetweenM.smithii,Bacteroides,andthehumangut,whymightoverweightstudysubjectshaveadifferentmethaneandhydrogenprofilecomparedtohealthyweightstudysubjects?


6.Whatniches,orspecificecologicalroles,haveM.smithiiandBacteroidesestablishedinthehumangutecosystem?


Group2:BacteriophageTherapy

Whenweheartheterm“virus”,whatpopsinyourhead?Negativeimageryofsickness,death,anddiseasemayreadilycometomind,butdidyouknowthatscientistsarenowactuallyharnessingthepowerofvirusestocombatbacterialinfections?Inthisreading,wewillfirstlearnaboutaspecifictypeofviruscalledabacteriophage.Wewillthentakealookathowscientistsareusingthesephagestofightagainstpathogenicbacteriathatcausediseaseinhumans.

Avirus isan infectiousparticlemadeofproteinsurrounding genetic information in the form ofDNA or RNA. Viruses depend upon a host forsurvival and reproduction, as they cannotreplicate on their own. A virus that exclusivelyinfectsbacteriaisknownasabacteriophage,orphageforshort.Thelifecycleofabacteriophagecanbeseeninthediagramtotheleft.Startingatthe top of the diagram, the bacteriophage willfirstattachtoabacterialcellandinjectallofitsgenetic information, or genome, into thebacterial cell. The virus will “hijack” the cell’sreplicationandtranscriptionmachinery inordertoreplicateandtranscribeitsowngenome.

Theviralgenomeactsasablueprinttosynthesizethenecessarypiecestoproduceandassemblemorephages inside the bacterium. The newly assembled phages then lyse the cell, causing the cellularcontentstospilloutalongwithallthenewlysynthesizedphagesintothesurroundings,wheretheycangoandinfectneighboringcells.Thistypeofphagelifecycleiscalledthelyticcycle.Incertaininstancesafterthevirusinfectsthecelltheyenterwhatiscalledthe lysogeniccycle.Duringthelysogeniccycle,theviralgenomeintegratesintothebacterialgenome.Thisviralgenomeisnowapartofthebacterialgenomeandsowhenthebacteriadividetheviralgenomealsodividesandallthebacterialprogenyalsohavethevirus.Thiswillcontinueuntilothersignalsaregiventothevirusthatwillmakeitgo intothelyticcycle. Itmaysounddangerous,butscientistsarebeginningtousephages inwhat iscalled“phagetherapy”.Antibiotics are widely known for their role in treating disease caused by microorganisms, but manybacteriahavedevelopedresistanceto thesedrugs, renderingsomeof them ineffective.Why is it thatwedon’tseewidespreadusageofphagetherapy?IfwegobacktothetimeoftheSovietUnion,itturnsout theRussianswere doing cutting edge researchonphage therapy and evenusedphages on theirsoldierstocombatdiseasessuchasdysentery.AroundthesametimeintheWest,penicillinantibioticswerediscoveredandresearchonphagetherapywasmoreorlessabandoned.Thescientificbarrierdueto the ColdWar isolated both sides from the others’ research; the Russianswere insulated from thediscovery of antibiotics and continued phage research. Likewise, the United States set aside phagetherapyinfavorofantibioticresearch.Itisonlynow,duetobacterialresistancetoantibiotics,thattheworldhasonceagainbeguntotakeinterestinphagetherapyasameanstocombatbacterialinfection.

So howdoes phage therapywork exactly? Aswe just learned, phages can lyse bacteria, so scientistshaveisolatedlyticphagesthatcanspecificallytargetcertainbacteriaandkillthem.Wewilltakealook

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atanexperimentdoneonmiceinfectedwiththebacteriumPseudomonasaeruginosa.P.aeruginosaisacommonbacteriumthatundercertaincircumstancescancause infections that canbe fatal. Scientistshave isolated a phage that specifically targets and kills P. aeruginosa. In the following experiment,scientists tested three different treatments. In the first treatment, mice were infected with P.aeruginosa.Inthesecondtreatment,miceweretreatedwithphage.Finallyinthethirdtreatment,theyinfectedmicewithP.aeruginosafirstandthenadministeredthephage.TheresultsoftheexperimentsareshowninTable1below.

TABLE1.Protectionstudies:efficacyofphagetherapyonP.aeruginosainfection

Treatment

#ofsurvivors/total#ofmice(%survival)

Expt1 Expt2 Expt3 CombinedexptP.aeruginosainfectiononly 0/6(0%) 1/6(16.7%) 2/6(33.3%) 3/18(17%)

Phageonly 6/6(100%) 6/6(100%) 6/6(100%) 18/18(100%)P.aeruginosainfection+Phage 6/6(100%) 6/6(100%) 5/5(100%) 17/17(100%)

Whataresomeoftheadvantagesanddisadvantagestophagetherapy?Oneadvantagetoantibioticsisthatphagescanevolve rightalongwith thebacteria. If thebacteriaevolve resistances tophages, thephageswillevolvetoovercomethatresistance.However,itisthissameabilitytoevolvethatbringsupquestionsofsafety.Theoriginalphageadministeredmightbesafetouseonahumanbodybutwhoistoknowwhatthisphagewillevolveinto?Antibioticsarecurrentlyasafermethodbecausetheydonotevolveand their effects arepredictable. The specificityofphagesalsoallows them toonly target the“bad”bacteria.Barringunforeseenevents,thephageswillnotkillanyoftheusefulor“good”bacteriathatareinourbodies.Antibioticsoftenindiscriminatelykillbacteriaandcaneliminatethegoodbacteriaalongwith the bad. There are currently no phage therapies authorized for human use in the UnitedStates but a lot of research is going into the technique. Phages used for combating food poisoningbacteriaarealreadyinuseinthefoodindustry.Inconclusion,phagetherapyisapromisingandexcitingnewtreatmentunderdevelopmentthatmayonedayhelpusinourissuescombatingbacterialinfection.ThisreadingwasdevelopedbyJoshuaChang,anMCB300HonorsstudentattheUniversityofIllinois,

Urbana-Champaign.

References:Campbell,A.(2003).Thefutureofbacteriophagebiology.NatRevGenet4:471–477.

Kantor,A.(July2006).U.S.Needstoopeneyesto'phagetherapy’.USATODAY.RetrievedAugust19,2014,from:http://usatoday30.usatoday.com/tech/columnist/andrewkantor/2006-07-06-phage-therapy_x.htm

McVay,C.,Velasquez,S.M.&Fralick,J.A.(2007).PhagetherapyofPseudomonasaeruginosainfectioninamouseburnwoundmodel.AntimicrobAgentsChemother:51.

Siringan,P.,Connerton,P.L.,Cummings,N.J.&Connerton,I.F.(2014).Alternativebacteriophagelifecycles:ThecarrierstateofCampylobacterJejuni.OpenBiology:130200.

Wikipediacontributors(July2014).Bacteriophage.Wikipedia,TheFreeEncyclopedia.RetrievedAugust19,2014,fromhttp://en.wikipedia.org/w/index.php?title=Bacteriophage&oldid=618512288

ExpertQuestions:

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7.


1.Diagramthelyticandlysogeniccycles.Whichcycleismostrelevantforphagetherapypurposes?2.Whyisphagetherapybeginningtoincreaseinpopularityagain?WhatwasthereasonthatitwasabandonedintheWest?3.Whyisthespecificityofthephagesoimportant?


4.BasedonthedatapresentedinTable1,whatisthepurposeofeachtreatmentandwhatdoeseachtreatmentprove?Doestheexperimentshowthatphagetherapyhaspotentialtocombatbacterialinfection?5.List3advantagesand3disadvantagestophagetherapy.Trytocomeupwithsomeofyourownreasons!


Group3:Microbeseducateimmunecells

Scientistsfrequentlyusemodelorganisms,ororganismswithcertaindesirablecharacteristics,tostudyvariousbiologicalphenomena.InonestudybyAtarashiandhiscolleagues,theteamusedmicetostudyhownativemicrobes,specificallyClostridium,contributetotheeducationofregulatoryTcells.RegulatoryTcellsareresponsibleforidentifyingwhichcellsofthehumanbodyare"self"and"foreign",andarealsoinchargeofregulatingwhentheimmunesystemshould“turnoff”afteraninvadingpathogenhasbeeneliminated.RegulatoryTcellsalsopreventautoimmunediseasesthathavebecomeincreasinglyprevalentinindustrializedsocieties,suchasallergies,asthma,andpsoriasis.PreviousresearchshowedthatmicrobesofthecolonhelpstimulateregulatoryTcellsandhelpthemtodiscernwhichtypesofmicrobesarehelpfulandwhichonesareharmful.IntheAtarashistudy,theteaminoculated(introducedasubstanceintothebodyof)2-weekoldmice,whichweregrowninalaboratorysettingthatdidnotallowthecolonizationofClostridium,withacontrolledamountofClostridium.Thisway,theycouldmonitorhowmuchClostridiumthemicewereexposedto.TheresearchteamwantedtoinvestigatewhetherClostridiumcouldnotonlystimulatetheproductionofregulatoryTcellsbutalsowhetherornotthisstimulationaffectedtheautoimmuneresponseofClostridiuminoculatedmice.TheresultsoftheirstudiesontheeffectsofClostridiuminoculationontheamountofregulatoryTcellsandvariousdiseasestates,suchascolitisandovalbuminallergy,arefoundinFiguresA,B,andC.

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Injected

with

Clostridium

Num

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FigureA:ThenumberofTcellsinmice1)notinoculatedwithClostridiumand2)orallyinoculatedwithClostridium.

DiseaseScore

NumberofDaysExposedtoDSS(d)

FigureB:Bothgroupsofmiceweretreatedwith2%dextransodiumsulfate(DSS)tosimulatecolitis,amodelofhumanirritablebowelsyndrome.Overthecourseof6days,themiceineachgroup(n=7)weremeasuredfortheirdiseasescore,whichwasdeterminedbytheseverityofbodyweightloss,stoolconsistency,andbleeding.

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References:Atarashi,K.,Tanoue,T.,Shima,T.,Imaoka,A.,Kuwahara,T.,Momose,Y.,…Honda,K.(2011).Induction

ofcolonicregulatoryTcellsbyindigenousClostridiumspecies.Science,331,337-341.Vignali,D.A.,Collison,L.W.,&Workman,C.J.(2008).HowregulatoryTcellswork.NatRevImmunol,

8(7),523-32.

Injectedwithprotein

Injectedwithprotein

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FigureC:Bothgroupsofmicewereinjectedwithovalbumin,aproteinthatinducesanallergicreaction,atweek0andweek2.Theamountofantibodyinthebloodserumofbothgroupsofmicewasrecordedtomeasuretheirallergicresponseoveraperiodof4weeks.

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Group3:Microbeseducateimmunecells

1.WhatroledoregulatoryTcellsplayindefendingourbodiesagainstforeignmicrobes?

2.InFigureA,howdothenumberofregulatoryTcellsinmicenotinjectedwithClostridiumcomparetothenumberofregulatoryTcellsinmicethathavebeeninjectedwithClostridium?

2b.WhatdoesthisimplyaboutClostridium’seffectonregulatoryTcells?


3.InFigureB,howdothediseasescoresdifferbetweeneachgroupofmice?

3b.WhatdoesthisdatatellusabouttheeffectsofClostridiuminoculationontheseverityofcolitis?

4.InFigureC,howdoestheamountofantibodydifferbetweenthetwogroupsofmice?


4b.Whatdoesthisdifferenceimplyregardingtheallergicresponsetoovalbuminineachgroupofmice?

5.Whattypeofniche,orecologicalrole,doesClostridiumplayinthehumangut?Wouldyousaytheyarebeneficialordetrimentaltothehumanbodyinthisexample?

5b.Intheexampledescribedinthereading,howareClostridiumandthehumangutinamutualisticrelationship(i.e.,howarebothorganismsbenefittingfromtherelationship)?


Group4:Microbesandtheblood-brainbarrier

Whathappenstothehealthofourbodiesifourmicrobesarenotkept“incheck”?Sometimeswecangetsickifcertainmicrobesthatarepartofourmicrobiomebegintogrowexcessively.Thisisthecasewithyeastinfections.Candidaalbicansispresentinourgastrointestinaltractbutcancauseinfectionsinotherpartsofthebodyifthehumanenvironmentchanges,i.e.takingcertainmedicationsoracompromisedimmunesystem.Thisoverpopulationofyeastdisruptsthenaturalbalanceofthehumanmicrobiome.

Othertimes,microbesenterpartsofourbodieswheretheyarenotwelcome.Forexample,Listeriamonocytogenesisapathogenic(diseasecausing)microbethatcanenterthebodythroughcontaminatedfoodandcausefoodpoisoningbycolonizinginthegut.Generally,ourimmunesystemscanfightoffListeriawhenitentersthegut,andsymptomsoffoodpoisoninglast24-48hours.Listeriacanalsoenterthecentralnervoussystem(CNS)causingmeningitis(meninges=membranesthatenveloptheCNS,-itis=infection).TheCNSisagenerallymicrobe-freeenvironment,andmicrobialinfectionscanbeextremelydangerous.Infectionsofthecentralnervoussystem,whichincludesthebrainandspinalcord,arerarebutcanhappenifthemicrobescrosstheendothelialcellsthatlinethebloodvesselsthatseparatethebloodfromthebrain.Generally,themicrobesfirstenterthebloodstreamandwhenthemicrobecountishigh,theycanbegintoattachtoand/or

damageendothelialcells,whichallowsthemtoentertheCNS.Figure1showsthethreedifferentwaysthatmicrobescanentertheCNS.Inthetranscellulartraversal(a),microbesbindtotheendothelialcellsviaproteinsontheirsurfacetoenterthecellsandthenexitontheothersideofthecell,thuscrossingfromthebloodsidetotheCNSside.Next,theparacellulartraversal(b)occurswhenthemicrobesdamagethetightjunctionsbetweentwoendothelialcellsinordertopassinbetweenthecellsandgofromthebloodtotheCNS.Finally,themicrobescanhitcharideonamacrophage(c),animmunecellthathas“eaten”themicrobe.Themacrophagecanmoveeasilybetweenthebloodandbrain,sowhenthemicrobesensesthatitisontheCNSside,itwillleavethemacrophagetogrowintheCNS.

Figure1:Threedifferentmechanismsofmicrobescrossingfromthebloodtothebrain.Imagefrom:Kim,2008,p.627


TheabilityforListeriatocrossfromthebloodintothebrain,andcauseamoreseriousinfectionforthehumanhost,issimilartotheinvasivespeciesphenomenonobservedinvariousecosystems.Invasivespeciesarethosethathavebeenintroducedintoanecosystem(eitherbyaccidentorbychanceasaresultofanotherevent)thattheydonotnormallyinhabit.InthecaseofListeriainfection,onceListeriahascrossedtheblood-brainbarrier,itcanquicklytakeupresidenceinthe(generally)microbe-freeenvironmentoftheCNSbecauseithaslittletonocompetitionofresources.Theimmunesystemthenhastoworktoeliminatethemicrobesthathaveinvaded,andhopefullyrestoretheCNSecosystemtoitspre-invasionstate.References:Kim,K.S.(2008).Mechanismsofmicrobialtraversaloftheblood-brainbarrier.NatureReviews:Microbiology. 6:625-634.



Group5:Microbesandtheblood-brainbarrier

1.Accordingtothereading,howcanmicrobes,suchasCandidaalbicans,thatarepartofahealthyhumanmicrobiomecauseillness?

1b.Describeanotherexampleoftheoverpopulationofacertainspeciesanditsimpactonanecosystem.

2.WhatarethethreetypesofwaysthatmicrobescanentertheCNS?


2b.Whatconditionmustbemetinorderformicrobestocrosstheblood-brainbarrier?

3.HowisListeriaaninvasivespecies?

3b.Describeanotherorganismthatisaninvasivespeciesanditsimpactonanecosystem.


Image shows A. baumannii infection in a patient’s leg following a gunshot wound.

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Group5:TheRiseofAntibioticResistantAcinetobacterinHospitalAcquiredInfections

Background:Acinetobacter isagenusof27differentspeciesofbacteria thatcanthrive inawidevarietyofhabitatsfrommoistsoiltodrysurfacesinahospitalroomtohumanskin.Thesebacteriaaretypically rod shaped, and are classified as Gram Negative, meaning they have a thin layer ofpeptidoglycanbetweentheir innerandoutercellmembranes.ManyspeciesofActinobacterarequiteresilient,assomeareevenabletogrowonbenzene,anorganiccomponentofcrudeoil that ishighlycarcinogenictohumans.

Clinical Significance:Microorganismsthatcauseinfectionanddiseaseareknownaspathogenicorganisms,orpathogens.Membersof thegenusAcinetobacterarenotalwayspathogenic;onestudy

showedAcinetobacter species thriving on the skin andin themucousmembranes of 43% of non-hospitalizedpeople sampled. However many species of this genusare known to be opportunistic pathogens, meaningtheycancauselife-threateninginfectionsinindividualswith compromised immune systems, typically causingpneumonia. One species, Acinetobacter baumannii, isthe fifth most common pathogen implicated innosocomial (hospital acquired) infections worldwide.SeveralfactorscontributetotheabilityofA.baumanniitowreakhavocinhospitals:

• GroupsofA.baumanni cancreatebiofilms,sticky filmsofpolysaccharidessecretedbythebacteriathatsurroundthemandactasaphysicalbarriertodisinfectantsandantibiotics.

• A. baumannii is able to survive totally dry surfaces, allowing them to persist on hospitalsurfacesuntilabletoreinfectasusceptiblepatient.

• Thespeciesisextremelyadeptatrapidlyacquiringantibioticresistance(anabilitythatwillbediscussedlater),makingtreatmentofinfectionsallthemoredifficult.

Mechanism of Resistance:Thereareawidevarietyofmechanismsbywhichbacteriacanresistdestructionbyantibiotics.Thesedrugstypicallytargetanaspectofbacterialphysiologynotpresent inhumans,buttherearefourmainmethodsbywhichbacteriamayescapethelethaleffectsofantibiotics:

• Thebacteriamayevolveanewversionofatraitthatwillescapetargetingbyaspecificdrug.Forexample, ifaspecificantibioticusuallybinds toand inactivatesbacterial ribosomes,avital tool for synthesizing proteins, a resistant bacterium may have evolved functionalribosomesthatdonotpossessthesitetargetedbythedrug.

• Biochemicalpathwayscanbeadapted tocreateproducts thateitherdestroyor inactivatethedrugwhenitentersthecell.

• Cells can prevent the drug from reaching lethal levels by either blocking their entry, orevolvingefflux pumps, proteins that shuttle thedrugoutof the cellbefore it candoanyrealdamage,somewhatlikedumpingwateroutaboatwithabucketbeforeitcansink.


• If a drug would typically block a vital biochemical pathway that most bacteria need toperformtosurvive,bacteriaresistanttothisdrugmayhaveevolvedanalternativepathwaythatisunaffectedbytheantibiotic,allowingthemtosurviveandgrowunhindered.

Asrecentlyasthe1970s,A.baumanniiwassensitivetoallknownantibiotics.Whatthen,hasalloweditto play such a major role in hospital acquired infections just 40 years later? For one, the ability ofA.baumannii to resist antibiotic treatment has since increaseddramatically. Samples ofA.baumanniithat are resistant to all antibiotics have been reported as early as 2008. Many of these multi-drugresistantstrainsofA.baumanniiareresistanttoanentirecategoryofantibiotics,knownasbeta-lactamantibiotics. This category includes commonantibiotics likepenicillin andampicillin,which functionbyblockingcellwallsynthesis inbacteria,causingthemtoburstwhentheytrytodivide.Thesedrugsarenamedfortheir“betalactam”ringintheirchemicalstructures.However,beta-lactamresistantbacteriacanproduceenzymescalledbeta-lactamasesthatdestroytheseringsanddisablethedrugbeforeitcandoalethallevelofdamage,allowingthebacteriatocontinueinfectingpatientstreatedwiththesebeta-lactamantibiotics.Thischangeintheantibiotic’schemicalstructureisdepictedbelow:

Wheredoes resistance come from?:Tousethepreviousexample,beta-lactamasescanonlybeproduced if thebacteriumpossessesagene in itsDNAthatcodesforthe informationnecessarytoproduce these beta-lactamase enzymes. The gene that allows these bacteria to produce beta-lactamases can exist on a small DNAmolecule separate from the rest of the bacteria’s DNA called aplasmid.Theseplasmidscanbetakenupfromtheenvironmentorswappedbetweenbacteria,allowingpathogens to build resistance by mixing and matching genes with completely different species ofbacteria. In a hospital environment,with plenty of exposure to different pathogens, each potentiallycarryingtheirowngenescodingforresistancetodifferentantibiotics,plasmidscanbeswappedreadily.Abaumannii isnotorious forbeingabletopickupanysurroundingDNA in theenvironment,allowingthemtogainantibiotic resistancecodinggenesextremelyquickly.This traitevolveddue to long-termcoexistence in the soil with othermicrobes that naturally produced their own antibiotics, leading tonaturalselectionfavoringstrainsofA.baumanniithatcouldquicklypickupantibioticresistancecodinggenesfromtheirsurroundings!

ResistanceWorldwide:A.baumanniihasbeenidentifiedasthecauseof1-2%ofallnosocomialpneumonia infections worldwide. According to the CDC’s Annual Threat Report, antibiotic resistant

Adap

tedfrom

UICCollegeof

Pharmacy.


organisms in theentiregenusAcinetobacteraccount for just .365%of infectionsand2.17%ofdeathscausedbyantibioticresistantpathogensannuallyintheUS.However,somestudiesofhospitalsinlessdevelopedAsianandMiddleEasterncountriessuchasIran,Taiwan,andIndiashowhigherratesofthesenosocomial infections due tomulti-drug resistant (MDR) Acinetobacter. Do these organisms showdifferences in rates of resistance across different parts of the globe? The graph below shows thepercentage of Acinetobacter that were found to be resistant to antibiotics in samples taken fromhospitalsinthreecountries.

TheriseofMDRbacteriaisonlymadeworsebyhumanmisuseandoverprescriptionofantibioticsacrossthe world. In countries like India and China, common antibiotics are available for purchase over thecounter,andacrosstheworldphysiciansprescribeantibioticsforillnessesnotevencausedbybacteria,like the common cold. By overusing common antibiotics like tetracycline, humans drastically increaseselection for antibiotic resistant bacteria, and accelerate their growth and spread. While promisingalternativesare indevelopment,suchasadministeringvirusesthatonlykill thepathogenicbacteria inthebody,antibioticsremainextremelyvitaltohealthcarepracticesacrosstheglobe.Newantibioticsarenotcreatedatasufficientrate,andoncetheremaining“lastresort”antibioticsarenolongereffective,previouslycommon,treatableinfectionscouldbecomemuchmorelethal.

ThisreadingwasdevelopedbyJesseBlack,anMCB300HonorsstudentattheUniversityofIllinois,Urbana-Champaign.

Datafrom

Hujeretal.2006,Kum

aretal.2013

andMalekietal.2014


References:BehzadniaS,DavoudiA,RezaiMS,AhangarkaniF.(2014)NosocomialinfectionsinpediatricpopulationandantibioticresistanceofthecausativeorganismsinnorthofIran.IranRedCrescentMedJ.16(2):e14562.

HujerKM,HujerAM,HultenEA,etal.(2006)Analysisofantibioticresistancegenesinmultidrug-resistantAcinetobactersp.isolatesfrommilitaryandcivilianpatientstreatedattheWalterReedArmyMedicalCenter.AntimicrobAgentsChemother.50(12):4114-23.

HsuehPR,TengLJ,ChenCY,etal.(2002)Pandrug-resistantAcinetobacterbaumanniicausingnosocomialinfectionsinauniversityhospital,Taiwan.EmergingInfectDis.;8(8):827-32.

KumarSG,AdithanC,HarishBN,SujathaS,RoyG,MaliniA.(2013)AntimicrobialresistanceinIndia:Areview.JNatSciBiolMed.;4(2):286-291.

MalekiMH,SekawiZ,SoroushS,etal.(2014)PhenotypicandgenotypiccharacteristicsoftetracyclineresistantAcinetobacterbaumanniiisolatesfromnosocomialinfectionsatTehranhospitals.IranJBasicMedSci,17(1):21-6.

RocaI,EspinalP,Vila-farrésX,VilaJ.(2012)TheAcinetobacterbaumanniiOxymoron:CommensalHospitalDwellerTurnedPan-Drug-ResistantMenace.FrontMicrobiol,3:148.

SebenyPJ,RiddleMS,PetersenK(2008)AcinetobacterbaumanniiSkinandSoft-TissueInfectionAssociatedwithWarTrauma.ClinInfectDis47:444–449

"ThreatReport2013."CentersforDiseaseControlandPrevention.CentersforDiseaseControlandPrevention,1Jan.2013.Web.7Aug.2014.UICCollegeofPharmacy."DrugInformationCenter."UniversityofIllinoisatChicago,n.d.Web.07Aug.2014.WinstanleyC,TaylorSC,WilliamsPA.(1987)pWW174:alargeplasmidfromAcinetobactercalcoaceticusencodingbenzenecatabolismbythebeta-ketoadipatepathway.MolMicrobiol.,1(2):219-27.


ExpertQuestions:

1. WhyisA.baumanniiabletopickupantibioticresistancemorequicklythanotherspeciesofbacteria?

2. WhymightpopulationsofA.baumanniiinhospitalsindevelopingcountriesshowdifferentratesofantibioticresistancethanthosefoundintheUSorCanada?Doyouthinktheproblemofresistancewouldbebetterorworseinthesedevelopingcountries?

3. Whatdoesitmeantobeanopportunisticpathogen?

4. Canyouthinkofanywaytotargetanddestroyspecificbacteriainthehumanbodythat

doesnotinvolveantibiotics?

5. AspecimenofA.baumanniipicksupaplasmidthatallowsittoberesistanttohighconcentrationsoftheantibioticchloramphenicol.Thisantibiotictypicallyblockstheability


ofbacteriatoproduceproteinsbybindingtoaspecificsiteontheribosome.CanyouthinkofamechanismbywhichthisplasmidcouldallowA.baumanniitoberesistanttothisdrug?

6. Drawapictureofthismechanismofresistance.


Group6:Usingmicrobesastreatmentofbacterialinfection

“PoopTransplants”MayCombatBacterialInfectionsArticleadaptedfrom:Rowan,K.(2012).“PoopTransplants”maycombatbacterialinfections.Live

Science.

"Pooptransplants"areaneffectivewaytotreatpeoplewithonetypeofintestinalbacteriainfection,anewstudyshows.

Researcherstransplantedfecalmatterfromhealthypeopleintothecolonsofpeopleinfectedwiththenotoriouslyhard-to-treatClostridiumdifficile(C.diff)bacteria(,whichcausessevere,waterydiarrhea.Theresearchersfoundthat46outof49patientsgotbetterwithinaweekofthetreatment.

Thetransplantworksbecausestoolfromhealthypeople,whenmixedwithwarmwateranddeliveredviaatubeintopatients'colons,helpsre-establishthenormalbalanceofbacteriaintheintestine.C.diffinfections

generallyoccurwhenaperson’snormalmicrobiomebecomesdisrupted,fromeitherantibiotictreatmentoraconditionthatleavespatientswithacompromisedimmunesystem.Withthetransplant,thelargeinfluxofhealthybacteriacanoutcompetetheC.diffforresources,essentiallycausingtheC.difftodieoffduetoalackofresources.

"C.diffisaseriousinfection—peoplediefromthis.Withthistreatment,thecurerateiscloseto100percent,"saidstudyresearcherDr.MayurRamesh,aninfectiousdiseasephysicianatHenryFordHospitalinDetroit.

Amongthe46patientsforwhomthetransplantwassuccessful,four(or8%)experiencedarecurrenceoftheirinfectionduringthefollow-upperiod.Bycontrast,studieshaveshownthatinfectionsrecurin25to30percentofpatientswhoreceivethestandardtreatmentforC.diff,whichisacourseofantibiotics,Rameshsaid.

Asofthreemonthsafterthefecaltransplant,thepatientshaddevelopednocomplicationsorsideeffectsasaresultofthetreatment,theresearchersreportedataninfectiousdiseasesresearchmeeting.

C.diffinfectionsarelinkedto14,000deathsintheU.S.yearly,accordingtotheCentersforDiseaseControlandPrevention.Peopleathighestriskfortheinfectionareolderadultsandthosewhotakeantibiotics.It'sbelievedthatantibioticsmaydisruptthenormalbalanceofbacteriaspeciesintheintestine,givingC.diffbacteriaachancetothrive.

Figure:ClostridiumdifficileCredit:CDC/LoisS.Wiggs.(2004)


PatientswithC.diffinfectionsaretypicallytreatedwiththeantibioticsmetronidazoleorvancomycin;however,thesedrugsdon'tworkforeveryone,theresearcherssaid.Inseverecases,patientsmayneedsurgerytoremovetheinfectedpartsoftheirintestines.

Inthestudy,researcherslookedatpatientswhoseaverageagewas65andwhoweretreatedwithfecalmattertransplantsoveratwo-yearperiodatthestudy’shospital.Inmostcases,thedonorwasthespouseorchildofapatient,butinsomecases,siblings,parents,orunrelatedpeopledonatedfecalmatter.

Thepatientswerenotmuchbotheredbythepossibleickfactorofthetreatment,RameshtoldMyHealthNewsDaily."Thesepatients,theysuffersomuchfromtheirsymptoms,"hesaid."WhenItellthemaboutthistreatment,theysay,'wow,thatmakessense,goaheadanddoit.'"Nopatientsdeclinedthetreatment,hesaid.

OtherstudieshavefoundasimilarlyhighpercentageofC.diffpatientscanbetreatedsuccessfullywithfecaltransplants.However,thenewresearchdifferedfrompreviousstudiesbecauseaboutathirdofthepatientshadsevereC.diffinfections."Thesearethepatientswhomaydie,orneedtohaveasectionoftheircolonremoved,"Rameshsaid.Otherstudieshavefocusedonpatientswithrecurring,butnotsevereinfections,hesaid.

Fourpatientsinthestudydied,includingthreewhoseC.diffinfectionhadbeensuccessfullytreatedwiththetransplant.ThedeathswereunrelatedtoC.diff,theresearcherssaid;allhadcancerbeforestartingthetreatment.

Whilethisstudyandotherssuggestthatfecalmattertransplantsareeffective,randomizedcontrolledtrialsareconsideredthe"goldstandard"ofevidenceinmedicine.

OnesuchtrialwasrecentlyapprovedtobeginintheU.S.Inthatstudy,patientswillberandomizedintotwogroups:inone,patientswillreceivefecalmatterfromhealthydonors,whileinthecontrolgroup,patients’ownfecalmatterwillbetransplantedbackintothem,accordingtoanarticlepublishedinSeptemberinthejournalClinicalInfectiousDiseases.

Passiton:FecalmattertransplantsmaybeaneffectivewaytotreatC.diffinfections.

ReferencesArticleadaptedfrom:Rowan,K.(2012).“PoopTransplants”maycombatbacterialinfections.LiveScience.Retrievedfrom

http://www.livescience.com/36701-poop-transplants-bacterial-cdiff-infections.html

Imagefrom:CDC/LoisS.Wiggs.(2004).Retrievedfrom

http://commons.wikimedia.org/wiki/File:Clostridium_difficile_01.jpg



Station6:Usingmicrobesastreatmentforbacterialinfection

1.Whatisafecaltransplant?

1b.HowdothemicrobesfromthefecaltransplanteliminatetheC.diffinfection?

1c.Inthehumangutecosystem,howdonativemicrobesprotecthumansfrominfectionsbymicrobessuchasC.diff?


2.WhatwastherateofrecurrenceoftheC.diffinfectioninpatientswhoreceivedthefecaltransplantcomparedtothosewhoreceivedthestandardantibiotictreatment?

2b.Whatcouldbepotentialnegativeconsequencesofafecaltransplant?

3.Whatarethenextsteps(accordingtothearticle)toinvestigatewhetherornotthefecaltransplantisamoreeffectiveoptionthanstandardantibiotictreatment?

Documents

Group 1: Microbes that affect our body weight