The Molecular Epidemiological Investigation And Carbapenemases Detection Of Carbapenem-resistant Acinetobacter Baumannii In North Sichuan

Objiective: To investigate the clinical characteristics and antibioticsusceptibility of Carbapenem-resistant Acinetobacter baumannii (CR-AB) innorth Sichuan.To understand the molecular epidemiology and drug-resistantfeatures of CR-AB, the homology analysis of gene will be made and the genesof carbapenemases will be detected.Methods: Collected90strains of imipenem and/or meropenem resistantAcinetobacter baumannii from two top three hospital in North Sichuan(one isaffiliated hospital north Sichuan medical college,short for hospital A;the otheris central hospitals of Nanchong,short for hospital B). The minimal inhibitoryconcentrations (MIC) for15antibiotics widely used in clinic were determinedwith double agar dilution method. The clinical data was retrospectiveanalysed. The homology analysis of gene was made by enterobacteriaceaeintergenic repetitive sequence of polymerase chain reaction (ERIC-PCR).Screening of Carbapenemases was made by modified Hodge test.Carbapenemases resistant genes such as OXA-23-like,OXA-24-like,OXA-51-like,OXA-58-like,IMP,VIM and drug-resistant gene of NDM-1superbugswere detected by PCR.Results: Sputum specimens was the most common specimens in the twohospitals: they were74%(37/50) and70%(28/40) in hospital A and Brespectively. The secretion was the second: hospital A and B were18%(9/50)and25%(10/40) respectively. The CR-AB had the most sections for Intensive Care Unit (ICU)26%(13/50) and37.5%(15/40), Neurosurgery20%(10/50)and15%(6/40), Respiratory department10%(5/50) and12.5%(5/40)respectively. The mean age of90patients was58.96±19.72years. Theunderlying diseases of these patients were cerebral disease (28.9%), chronicobstructive pulmonary disease COPD (28.9%), tumor (12.2%), heat burning(7.8%), fracture(7.8%), and other diseases (14.4%). The organ failure of thesepatients was: respiratory failure(44.4%), coma caused by brain dysfunctions(35.6%),Multiple Organ Dysfunction Syndrome (13.3%).The situation ofpatients before CR-AB infection was: staying in ICU(70%),artificialrespiratory tract or mechanical ventilation(60%), invasive procedure(88.9%)and47.8%had operation,used three or more antimicrobial agents22.2%.Theprognosis was unhealed or death(34.4%) and average admission time was50.3days.The rate drug resistance of CR-AB to polymyxinB,minocyline,cefoperazone/sulbactam and piperacillin/tazobactam was0%,20.0%,28.9%and86.7%. The rate drug resistance of CR-AB for other drugs was100%andMIC90of some drugs≥512μg/ml.Detection rate of multi-drug resistance(MDR)strains and extremely-drug resistance(XDR)strains were100%and47.8%. Five genotypes which cloned spread occurred at2hospitals werefound by ERIC-PCR genotyping in90CR-AB strains. Modified hodge testfound that72strains were positive (80%,72/90).All of the strains(100%,90/90)carried OXA-51-like gene,79strains(87.8%,79/90) carried OXA-23-like geneand the expansion of rest genes was negative.Conclusions: The CR-AB strains were found main in ICU,neurosurgeryand respiratory department.The patients complicated with underlying diseasesare more severe and undergo invasive procedure frequently.The location ofinfection was mainly the lung.Most of CR-AB were multi-drug resistance strains or extremely-drug resistance strains. The resistance rate of CR-AB topolymyxinB, minocyline and cefoperazone/sulbactamand were low, and sothese three drugs maybe the efficient for CR-AB.Acinetobacter baumanniicould transmit in different departments of hospital,and advantage of genotypenot be exactly the same in different hospitals.So medical workers shouldenhance risk awareness of the nosocomial transmission of the pathogenicbacteria to decreasing the chance of nosocomial infection. The drug-resistantmechanism of CR-AB was related to the OXA-23-like Carbapenemases andno other Carbapenemases was found in north Sichuan.