| Objective:Acinetobacter baumannii is one of the most common pathogens of nosocomial infections,including ventilator-associated pneumonia,bloodstream infection,meningitis and urinary tract infection.With the increasing detection rate of carbapenem-resistant Acinetobacter baumannii,the role of carbapenems is becoming more and more limited.As the last line of defense for the treatment of AB infection,it may face the dilemma of no drug available in clinic.The drug resistance of AB is related to efflux pump,quorum sensing and biofilm.Therefore,clinical data analysis of 54 AB strains in our hospital was carried out to study the distribution of AB efflux pump and quorum sensing genes,the correlation between biofilm formation ability and drug resistance,and the effect of efflux pump inhibitor Carbonyl cyanochlorphenylhydrazone(CCCP)on biofilm formation.In-depth understanding of AB resistance mechanism provides a scientific theoretical basis for effective prevention and control of AB infection.Methods:1.A total of 70 Acinetobacter baumannii samples were collected from the Second Hospital of Shanxi Medical University from March 2022 to September 2022.The samples were identified by MADLDI-TOF-MS,the unqualified strains and repeated strains were removed,and the drug sensitivity test was carried out.37 CRAB strains and17 CSAB strains were selected and the clinical date were analyzed.2.Phenotypic detection of RND efflux pump genes ade G,ade B,ade J and quorum sensing genes aba I,aba R in CRAB and CSAB strains was performed to compare the positive rates between the two groups.The efflux pump genes ade G,ade B,ade J were sequenced to analyze their homology.3.The MIC of efflux pump inhibitor CCCP was determined by broth microdilution method.The biofilm formation ability of AB and the effect of different concentrations of CCCP on the biofilm formation ability of AB were determined by crystal violet staining.Results:1.Among the 54 AB clinical isolates,Respiratory tract specimens accounted for87.05%(47/54).The results of department distribution showed that ICU,respiratory department and neurosurgery were the main areas of AB distribution,accounting for70.37%.Among the 54 patients with AB infection,Patients over 65 years old accounted for 46.3%,of which 80% had underlying diseases,61.1% had mechanical ventilation and53.7% had central venous catheterization.2.In 37 CRAB strains,the positive rate of aba I gene was 94.6%(35/37),aba R was89.2%(33/37),ade G was 91.9%(34/37),ade J was 100%,and ade B was 91.9%(34/37).In 17 CSAB strains,the positive rate of aba I gene was 70.6%(12/17),aba R was 41.2%(7/17),ade G was 64.7%(11/17),ade J was 100%(17/17),ade B was 23.5%(4/17).The positive rate of aba I,aba R,ade G and ade B genes in CRAB group was higher than that in CSAB group(P<0.05).3.Among the 36 strains,only 2 sensitive strains could not form biofilm and the positive rate of biofilm was 94.44%.Among them,11 strains(30.56%)were strongly positive,16 strains(44.44%)were positive and 7 strains(19.44%)were weakly positive.The biofilm formation ability of CRAB group was higher than that of CSAB group(P<0.05).4.Eight AB strains with strong biofilm formation ability were randomly selected to detect the effect of efflux pump inhibitor CCCP on biofilm formation ability.Compared with the control group,When CCCC was 4ug/ml,there was no significant difference in biofilm formation ability.When CCCP was 8ug/ml-12ug/ml,AB biofilm formation was inhibited to varying degrees.The higher the concentration,the more significant the inhibition(P<0.05).Conclusion:1.AB in our hospital mainly causes respiratory tract infection,especially ventilator-associated pneumonia and bloodstream infection.Patients with ICU hospitalization,advanced age,underlying diseases,and invasive procedures are susceptible to AB.2.ade B,ade G,aba I and aba R genes were associated with CRAB acquired resistance,and ade J gene was associated with AB inherent resistance.3.Biofilm played an important role in CRAB resistance.4.Efflux pumps contribute to AB biofilm formation. |
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