Study On Drug Resistance Mechanisms And Epidemiology Of Carbapenem Resistant Acinetobacter Baumannii

Objective The study was analysized to test the drug susceptibility and check drug-resistant genes among Acinetobacter baumannii gathered from patients in Tianjin Medical University General Hospital.To investigate the relationship between carbapenem and active efflux pump system and carbapenem-resistant Acinetobacter baumannii,to explore the risk factors and molecular epidemiology of CRAB.It can provide a strong basis for the clinical diagnosis and prevention of CRAB infection,to prevent and control the spread of the resistant strains in the hospital.Methods 79 non-repetitive carbapenem resistant Acinetobacter baumannii were isolated from 2011 to 2015 from the lower respiratory tract and aseptic body fluids of the inpatients.EDTA double disk test and carbapenem inactivation method were used to detect carbapenemases phenotype,PCR was applied to detect antimicrobial-resistant genes,including carbapenemases genes?blaOXA-51?-like ?blaOXA-23)-like? blaOXA-24-like ?blaOXA-58-like?bla IMP ?bla VIM ?bla SIM? bla NDM)and active efflux pump genes?ade B?ade R?ade S?ade J?ade G?.A case-case-control study and retrospective analysis were carried out to analyze the risk factors and clinical outcome of CRAB infection,the clinical characteristics of patients,including age,gender,department,basic disease,acute physiology and chronic health evaluation II,invasive operation,hospitalization time,the use of antibiotics before 3 months infection and prognosis,The risk factors of nosocomial infection were analyzed with univariate analysis.The independent risk factors were served from the risk factors with P<0.05 with multivariate regression analysis.The clonal dissemination of CRAB strains was detected by pulsed field gel electrophoresis?PFGE?.Results?1?A total of 79 isolates of CRAB identified during a period ranging from 2011 to 2015,the lower respiratory tract specimens were the main,accounting for 29.1%,the patients were mainly from the ICU,accounting for 45.6%.The resistance to gentamicin,ciprofloxacin,levofloxacin is high,The sensitivity rate of tigecycline and cefoperazone-salbactam were high.?2?Carbapenemase genes bla_OXA-51 were presented in all 79 isolates,and 97.5% of isolates carried the bla_OXA-23 gene,but bla_OXA-24-like,bla_OXA-58-like,bla_IMP,bla_VIM,bla_NDM,bla_SIM genes were completely absent in all isolates.The positive rate of ade B? ade R ?ade S? ade J? ade G were 83.54%?63.29%?73.4%?97.47%?94.94% respectively.?3?Multivariate logistic analysis showed that the independent risk factors of CRAB were that the infection of bacteremia/sepsis,usage of carbapenems,CVCs,indwelling catheter?3 days;the independent risk factors of CSAB were the usage of third-generation cephalosporin and CVCs.?4?Fifteen clones were detected by PFGE,A and C clones were predominant and persistently transmitted in different wards of the hospital named,clone C was the predominant clone in 2012,it was displaced as the predominant clone by clone A from 2013 to 2015.clone A was first detected in 2013,it was highly resistant to imipenem and moderately resistant to meropenem;The presence of clone A was associated with CVCs and previous use of carbapenems?P<0.05?.Clone C was moderately resistant to imipenem and lowly resistant to meropenem.it was associated with previous use of third-generation cephalosporins?P<0.05?.Conclusion The resistance rates of CRAB to gentamicin,ciprofloxacin,levofloxacin were high,the sensitivity rates to tigecycline,cefoperazone sulbactam were high.OXA-23 carbapenemase gene and active efflux pump genes were the main resistance mechanisms.Long-term use of antibiotics and invasive medical procedures were associated with CRAB infection.Rencently,A clone is the major prevalent clone type in our hospital,which has highly resistance to imipenem and meropenem,and A clone was associated with central venous catheterization.Strict control of invasive procedures and reasonable use of antibiotics may reduce the infection of CRAB.