Study Of Internal And External Antibacterial Effect Of Doirpenem And Combined Administration To Different Carbapenemases Genotyping Of Acinetobacter Baumannii

Acinetobacter baumannii is a sugar-azymic and aerobic Gram-negativefermentation,and one of common pathogens causing hospital infections. In recentyears, with the application of broad-spectrum antimicrobial drugs, glucocorticoids,Acinetobacter Acinetobacter infections have become a major pathogen of hospitalinfections and opportunistic infections, caused great difficulties to clinicalanti-infection treatment and hospital infection control.Carbapenem antibiotics is a small-molecule, efficient, broad-spectrumβ-lactams, most widely and strongest antibacterial activity antibiotics until now, andhighly stable to variety of β-lactamase, it is mainly applicable to serious bacterialinfection caused by multi-resistant bacteria and enzyme production-bacteria.Aswide range applications of antimicrobial agents, especially carbapenems,Acinetobacter baumannii resistantance continuously increased,like multi-drugresistant Acinetobacter baumanii and pan-resistant Acinetobacter baumanii.Resistance of multidrug-resistant Acinetobacter baumanii to carbapenem antibiotic ismainly caused by producing carbapenemases.Carbapenemases,which can bedivided into three categories: A type, is a serine protease; B type, is a metal β-lactamenzyme; D type, is a oxacillin enzyme(OXA-type)， which can only be found inAcinetobacter.A type is not yet in found Acinetobacter genus. Acinetobacterbaumannii producing carbapenemases are type B and D: B type (metalloenzymes)contains VIM and IMP, D type (OXA-type enzyme) were found more than20speciesin Acinetobacter, dividing into four groups.In recent years, mutants select windows theory considerd: When combination oftwo antimicrobial agents with different mechanisms act, beyond each MIC, thebacteria need have two resistance mutations to close the MSW, in order to controlbacterial resistance effectively. Therefore, when Acinetobacter baumanii resistant toall antimicrobial agents, combination therapy may be best treatment.As a result, this experiment select a new broad-spectrum carbapenem antibiotics-doripenem,to study its monotherapy and combined sensitivity. Doripenemis stable to mostβ-lactams. Comparing with imipenem and meropenem, possibility ofinduce bacteria producing drug resistance is lower.The study has clinical trials with doripenem(Zhengdatianqing PharmaceuticalCompany, and meropenem (Zhuyou Pharmaceuticals Company),to treat282cases ofsevere and acute respiratory bacterial infection. Results: clinical curing rate ofrespiratory disease patient are89.55%and85.07%, clinical curing rate ofcommunity-acquired pneumonia are85.71%and71.43%; bacterial clearance rateswere96.43%and98.21%; clinical curing rate of respiratory comprehensive efficacyare96.43%and91.30%.On this basis, the experiment detect76carbapenemase gene of Acinetobacterbaumannii,detect MIC of monotherapy and combination theapy of doripenem todifferent genotyping of Acinetobacter baumannii, through FIC index to judge whetherit has a synergistic effect. In further vivo experiments, we verify that comparing withsingle-agent,whether combination therapy has a better effect to Acinetobacterbaumannii infection in rats, exploring combination therapy to pan-resistantAcinetobacter baumannii, to guide clinical treatment.PartI Dection of carbapenemases genes in76Acinetobacter baumannii blaOXA-23、blaOXA-24、blaOXA-58、blaOXA-51、blaIMP-1、blaIMP-2、blaVIM-2Methods: Collecting76Acinetobacter baumannii from July2010to May2011inShanghai Changzheng Hospital,amplified by RT-PCR and assay sequencingcarbapenemase gene: blaOXA-23、blaOXA-24、blaOXA-58、blaOXA-51、blaIMP-1、blaIMP-2、blaVIM-2.Results:In76Acinetobacter baumannii,we decet blaOXA-23、13blaOXA-24、76blaOXA-51、10blaOXA-58、22blaIMP-1、15blaIMP-2、23blaVIM-2,which number are53、13、76、10、22、15、23.From highest to lowest：blaOXA-51、blaOXA-23、blaVIM-2、blaIMP-1、blaIMP-2、blaOXA-24、blaOXA-58，which ratio are100.0%、69.7%、30.3%、28.9%、19.7%、17.1%、13.2%.12plants with1type gene，28plants with2type genes，17plants with3type genes，12plants with4type genes，5plants with5type genes，2plants with6type genes. Conclusions:In different genotype of Acinetobacter baumannii,ratio from high tolow are: blaOXA-23、blaOXA-24、blaOXA-58、blaOXA-51、blaIMP-1、blaIMP-2、blaVIM-2.PartII Susceptibility of monotherapy and combination to Acinetobacterbaumannii with different carbapenemases genotypingMethods:We used microdilution method to detect minimum inhibitoryconcentration (MIC) of single agent levofloxacin, amikacin, sulbactam, doripenem,imipenem,meropenem and doripenem combined with levofloxacin, amikacin,sulbactam, to76Acinetobacter baumannii drug, and calculate the MIC50、MIC90; weused checkerboard to decect minimum inhibitory concentration of combination(doripenem+levofloxacin, doripenem+amikacin, doripenem+sulbactam);Comparing combination FIC distribution to explore effective combined way.Results: After combination therapy, MIC50、MIC90decreased. The FIC indexdistribution: the doripenem+levofloxacin, doripenem+amikacin, doripenem+sulbactam:FIC≤0.5:55.3%,52.6%,60.5%;0.5<FIC≤1:25.0%、22.4%、21.1%;1<FIC≤2：14.5%、13.2%、13.2%;FIC>2：5.3%、11.8%、5.3%.combination of antimicrobial drugswith doripenem, showed synergistic and additive effect, especially synergies, lowunrelated effect and antagonism effect. According to blaOXA-58Acinetobacterbaumannii, doripenem combind with sulbactam had lower FIC ratio. To blaOXA-58Acinetobacter baumannii, doripenem combind with levofloxacin, amikacin had lowerFIC ratio.Conclusions: After combination of antimicrobial drugs with doripenem,it showedsynergistic and additive effect, especially synergies, low unrelated effect andantagonism effect. Towards blaOXA-58gene, Doripenem combined with sulbactam, hada high sensitivity.Towards blaOXA-23gene, Doripenem combined with levofloxacin oramikacin, had a high sensitivity.PartIII Effect of combination therapy to mice with Acinetobacter baumanniiinfectionsMethods:In airway of mouse,we instilled Acinetobacter baumanniiATCC19606,to create mice infection model of Acinetobacter baumannii. Two daysafter model set up,we given single drug levofloxacin, amikacin, sulbactam, doripenem, meropenem,imipenem, and combination therapy (doripenem+levofloxacin, doripenem+amikacin, doripenem+sulbactam), comparing with controlgroup and normal group, observing mice lung tissue pathology, neutralgranulocyte,TNF-α, MPO, NK cytoactive to compare effect of single-agent andcombination therapy to body infection.Results:In Acinetobacter baumannii infection models, doripenem combinedwith levofloxacin group,compared with levofloxacin group, inflammatory extravasatedecreasing,TNF-α, MPO, NK cytoactive decreased significantly(P <0.05);doripenemcombined with amikacin group, compared with amikacin group, inflammatoryinfiltration decreasing;neutrophils number, MPO,NK cytoactive are significantlylower(P <0.05); doripenem combined with sulbactam, compared with sulbactamgroup,inflammation decreasing obviously;neutrophils number, TNF-α is significantlylower(P <0.05).Conclusions:After doripenem combined with levofloxacin, amikacin, sulbactam,comparing with single drug,it could not only obviously reduce mice plumonaryinflammation;but significantly reduce neutrophils,TNF-α,MPO,NK cytoactive ofAcinetobacter baumannii mice (P <0.05).In summary,combination of doripenem can produce better internal and externalefficacy towards carbapenemases with different genotyping Acinetobacter baumannii.