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Only79%ofbacteriaisolatedbyco-infectioncorrespondtopneumoniaassociatedwithmechanicalventilationorassociatedwithhealthcarewhile21%correspond toinfectionsof thepleuralfluidcatheterinfectionsbacteremiaandurinarytractinfectionsAhighnumberof strainsresistant tobeta-lactamsareobservedbothforpenicillinanditsderivativeswith100%penicillinderivativeswithbeta-lactamaseinhibitorsuchasampicillin/sulbactamamoxicillin /clavulanicacidpiperacillin / tazobactamalsowitharesistanceof100%Inthecaseoffirstsecondthirdandfourthgenerationcephalosporins100%resistanceisobservedexcept forceftazidime whichpresentsresistanceofonly963% thankstothesusceptiblestrainsofStenotrophomonasmaltophilia.ForEsbL-producing strainshighresistance topenicillinsandcephalosporinsisexpectedduetotheirenzymaticactivity(21)forthecaseofcarbapenemase-producingstrainstheyalsoexplainthehighresistanceindextobeta-lactams(22)alreadymentionedaswellasthecarbapenemicsmeropenemertapenemandimipinemresistanceof839“5%and897%respectively. thestrains with thehighestproductionofcarbapenemasesinthisstudyarePseudonomasaeruginosaXDrandAcinetobacterbaumanniiXDrInthecaseofhighlevelsofresistancetoallbeta-lactamsforStaphylococcusaureusitisexplainedbyresistancetomethicillinwhichimpliesnotanenzymebutthemodificationofthePbPPenicillin-bindingProteinsthatconfersresistancetoallbeta-lactams(23)Quinoloneresistanceiscausedbyvariousmechanismsparticularlyplasmid-ediatedquinoloneresistance(PMQr)whichcontains thepentapeptiderepeat familyQnrproteins(QnrAQnrbQnrsQnrcandQnrD) theseproteinsconferquinoloneresistancebyphysicallyprotectingDnAgyraseand topoisomeraseIV fromquinoloneactsthisconditionmayprovideaselectiveadvantageforthedevelopmentofquinoloneresistancewhichcouldresultintherapeuticfailure(24)QuinoloneresistanceismorecommoninEnterobacteriaceaethatshowresistancetobeta-lactamsduetotheproductionofextended-spectrumbeta-lactamases(EsbL)acquiredclasscbeta-lactamasesorcarbapenemases(25)AstudycarriedoutbyLópez-Jacomeandcollaboratorscarriedoutinthesecondhalfof2019andthesecondhalfof2020in 35healthcenters throughoutMexicocompares theresistanceacquiredbygrampositivesandgramnegativesfindingresistanceofupto100inS.aureusresistanttooxacillinaswellasupto50%increaseinresistancetoerythromycinandclindamycinAswellasresistancepatternssimilartocarbapenemsandfluoroquinolonesbygramnegativesandnon-fermenters(26)Oneofthegreatlimitationsinthestudywasnothavingthemeans tocarryoutadetailedcharacterizationat themolecularlevelof thedifferentcarbapenemasesexpressedby theisolatedMDrandXDrorganismsaswellastheEsbLoftheproducingstrainswhichwouldallowustoknowthemechanismsexactresistanceoftheantibioticsusedintheantibiogramandgiveacorrectdirectedtherapy.foundamongwhichceftazidimeandceftriaxonestoodoutaswellasa treatment with the fluoroquinolonelevofloxacinbothantibacterialtreatmentsadministeredsimultaneouslyfromadmissiontotheIcUInourstudy,initially100%of thestudypatientsand thosewhodidnotenterthestudyduetoexclusioncriteriahadtheaforementionedprophylacticantimicrobial therapy,something thatcontrastswithastudycarriedoutbyVaughnetal.Whoreportedtheuseofempiricalantibioticsin 566%ofcOVID-19patientsadmittedto38MichiganhospitalsInthatstudy,empiricaluseofantibioticsranged from 27% to84%amonghospitalsand themost frequentlyprescribedantibioticwasceftriaxonein389%Althoughtheprevalenceofbacterialcoinfectionsonadmissionislow(24-7%)empiricalantimicrobial treatmentisextremelycommon(72-90%)(15)takingintoaccount theamountofbacterialcoinfectionsinpatientswiththediseaseofthecOVID-19solow,theWorldHealthOrganizationsuggestednotusingantibioticstotreatthedisease(16)Ontheotherhandtheuseoflevofloxacinisjustifiedasaninitialtreatmentfornosocomialpneumoniaorcommunity-acquiredpneumoniadue toits wide spectrumandgoodconcentrationachievedin thelungs(17)as wellas theuseof third-generationcephalosporinssuchasceftriaxoneatadoseof1and 2g(18)However,whenpresentingaco-infectionofbacterialetiology,Imodifythetreatmenttoatargetedtherapyinmostcasesthisprophylactictreatmentwasusedfor7to10daysaccordingtotheresultsoftheculturesperformedwhereantimicrobialtherapyhadtobescaledtocarbapenemicscolistin vancomycinorlinezolidaccording to theisolatedmicroorganismsHowever,resistancetoantibioticssuggeststhatbacteriaalreadyhaveresistancetomostofthedrugsofeachoftheantimicrobial families(19)and thatitgives themaclassificationofExtremelyDrugresistantofwhichthereare84strainsandMultiDrugresistantwith12strainsInastudybyLiJetal.Atotalof159strainsofbacteriawereisolatedfrom theculturesin the102patients Among theisolatedbacteriaGramnegativebacteriawerethemainbacteriarepresenting855%thethreemainbacteriawereAcinetobacterbaumannii(A.baumannii,358%)Klebsiellapneumoniae(K.pneumoniae, 308%)and Stenotrophomonasmaltophilia(S.maltophilia,63%)(20)Whileinourstudy,theGrampositivebacterium Staphylococcusaureusrepresentsa totalof 38%of theisolatesand100%inresistancetomethicillinbytheoxacillintestandthecefoxitintestOntheotherhandinGramnegativeisolatesPseudonomasaeruginosawith 23%and Stenotrophomonasmaltophiliawith 20%of the totalof theisolates were theones thathad thehighestfrequencyinthetotalofsamplesAcinetobacterbaumanniiwhichinLisstudy was themostisolatedbacteriuminourstudy,representsonly5%oftheisolates128ANALESRANFwwwanalesranfcomResistencia alos antibióticoseninfecciones asociadas ala atencióndelasaludenlapandemiadeCOVID-19JorgeAAlmeidaVillegasJoséAGutiérrezGutiérrezetalAnRealAcadFarmVol88Nº2(2022)·pp123-130