A Study On The Structure Of Class â…  Integron And ISCR1and The Related Prevalence Of Acinetobacter Baumannii

Acinetobacter baumannii (Ab) is a gram-negative, non-fermenting organism and this organism is characterized by its strong environment adaptiveness and its ability to acquire antimicrobial resistance rapidly.Acinetobacter baumannii is widespread in the hospital environment,which could lead to nosocomial infections and prevalence easily.It’s necessary to monitor and analyze the distributions of Acinetobacter baumannii and its resistance,also it is of great importance for using antimicrobial agents reasonably and preventing and controlling the outbreak of nosocomial infection. Homologous analysis of bacterias isolated from hospital is an important content of epidemiology survey. It helps to understand the roots and the means of transmission and to take the actions in time and effectively. Random amplified polymorphic DNA (RAPD) is a easy,fast and high sensitive method which is usually be used as the epidemiology survey of Acinetobacter baumannii. Mobile genetic elements such as conjuagal plasmid,integron,transposon and insertion sequence common region (ISCR) are involved in horizontal transfer of the resistance genes between the same species and even different species of bacteria.The research reports on the complex class I integron have increased a great deal in recent years.The complex class I integron is composed of integron I and ISCRl,and it has been drawn much attention because of its ability to gathere and spread resistance genes.Objective:To investigate the antibiotic resistance and distribution feature of Acinetobacter baumannii strains isolated from a Third-level Grade A hospital in Tianjin from July2010to June2011. Homologous analysis of51multidrug-resistant Acinetobacter Baumannii isolates of intensive care unit (ICU) were carried by RAPD.To investigate the distribution and the antibiotic resistance genes carried by class I integron and ISCR1among multidrug-resistant Acinetobacter Baumannii clinical strains isolateed from ICU.Method:Specimen source,department distribution and antibiotic resistance of Acinetobacter Baumannii isolated from hospitalized patients from July2010to June2011were analyzed by WHONET5.4software and SPSS17.0software.Resistance rates of bacterias isolated from ICU and non-ICU were compared; Analysis of gene typing of51multidrug-resistant Acinetobacter Baumannii were performed by RAPD;Class I integrase gene Int Ⅰ,variable region of Class I integron,ISCRl,genes related to antibiotics resistance located downstream of ISCR1and the relationship between Class I integron and ISCR1in51multidrug-resistant Acinetobacter Baumannii were performed by Polymerase Chain Reaction (PCR),PCR-mapping and DNA sequencing.Results:1.A total of616Acinetobacter baumannii strains were collected.The616strains of Acinetobacter baumannii were primarily isolated from respiratory secretions (accounting for83.1%).Acinetobacter Baumannii resistance rates to polymyxin B, cefoperazone/sulbactam and levofloxacin were0%,20.1%and45.8%.The resistance rates of Acinetobacter baumannii to other surveillanced antibiotics were all above55.0%.About66.9%of these strains were collected from ICU,and the overall prevalence of multidrug-resistant Acinetobacter Baumannii were76.5%.Resistance rates of Acinetobacter baumannii isolated from ICU were obviously higher than organisms that isolated from non-ICU(polymyxin B was not included).Also multidrug-resistant rates of Acinetobacter baumannii isolated from ICU (85.4%) were more serious than organisms isolated from non-ICU (57.4%).2.51multidrug-resistant Acinetobacter Baumannii isolated from ICU were divided into5genetypes,and the A genetype was the major(49.0%,25/51).3.45strains isolated from ICU were found containing class Ⅰ integrase g-enes,and32strains were found containing variable regions.Sequencing results:the gene cassette arrays were aacA4-catB8-aadA1,aacC1-orfA-orf-B-aadA1and blaPSE-1-aadA2-cmlA1-aadA1;22strains were found containing ISCR1and5st-rains were found containing resistance genes located downstream of ISCR1,Se-quencing results:qnrA1-ampR.The results of PCR-mapping showed that ISCR1located directly downstream of3’conserved segment of class Ⅰ integron in20Acinetobacter Baumannii strains.Conclusions:1.Resistance rates to cefoperazone/sulbactam and levofloxacin of the Acin-etobacter Baumannii isolated from this hospital were relatively low,and the re-sistance rates of Acinetobacter baumannii to other β-lactams,Carbapenem.amin-oglycosides and parts of Quinolones and antimicrobials contained β-lactamase inhibitors were very serious.Organisms resistant to polymyxin B were not fou-nd.The overall prevalence of multidrug-resistant Acinetobacter Baumannii of t-his hospital was relatively high (accounting for76.5%).2.Resistance rates and multidrug-resistant rates of Acinetobacter baumannii isolated from ICU were more serious than organisms isolated from non-ICU.3. The results suggest that there existed cloning spread between different strains in this hospital.4.Class Ⅰ integrons were widespread in multidrug-resistant Acinetobacter Baumannii and play an important role in mechanisms of drug resistance to many antibiotics especially aminoglycosides. Quinolones resistant gene qnr can be carried by ISCR1in Acinetobacter Baumannii; Class Ⅰ integron and ISCR1may be involved in horizontal spread of resistant gene in local between different AcinetobacterBaumanni genetypes.Class Ⅰ integron and ISCR1connect in series mostly in AcinetobacterBaumanni.