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Studies on Relationship of ISCR1 and Drug Resistant Genes in Enterobacteriacea Resistant Clinical Isolates

Author: WuXiaoMei
Tutor: SongShiZuo
School: Tianjin Medical University
Course: Internal Medicine
Keywords: Enterobacteriacea drug resistant gene horizontal spread mobile elements ISCR1
CLC: R446.5
Type: Master's thesis
Year: 2011
Downloads: 34
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Abstract


After plasmid、integron and transposon, ISCR1 is a novel and powerful horizontal transmission media of resistant genes,which was located on complex class 1 integron in Enterobacteriaceae and were closely associated with many antibiotic resistant genes.Object To investigate the resistant phenotype and distribution of ISCR1 in 104 Enterobacteriacea resistant clinical isolates from one hospital in Tianjin during 2009 and 2010. Study the plasmid mediated mechanisms of microbiotics resistance and the gene context downstream of ISCR1 among 17 ISCR1 positive resistant strains, to discuss the roles of ISCR1 in microbiotics resistant gene broadcasting.Method The MICs of 12 antibiotics were determined by micro—dilution broth method. The orf513 gene in element ISCR1 was examined with PCR and DNA sequencing and blasting. ESBLs phenotypic confirmatory test were tested by double disk diffusion method. Three-dismensional extract test was tested AmpC enzyme.The CTX-M-ESBL gene 1 and 9 group、SHV、TEM、ampC、qnrA、qnrB、armA、rmtB gene were amplified by PCR or multiple PCR and analysed by PCR-SSCP or DNA sequencing.The gene context downstream of ISCR1 was tested by PCR-mapping.Result1、The drug resistant rate of 12 antibiotics CPR、CFP、CRO、CTX、GM、PPT、CAZ、CIP、OFX、LEV、AMK、CPS were 46.15%,64.42%,57.69%,83.65%,64.42%, 66.35%,73.08%,80.77%,78.85%,22.12%,26.92%,67.31%. Multiple drug-resistant strains were 58 strains, rate of multiple drug resistance is 55.77%(58/104).2.、17(16.35%) strains had positive result of PCR orf513 gene and were proved by DNA sequencing.Including 5 Escherichia coli.,4 Klebsiella,5 Enterobacter cloacae,1 Enterobacter aerogenes,1 Citrobacter freundii,1 JiGe fe enterbacteriaceae.3、17 ISCR1 positive strains’drug resistant rate of 10 drugs were more than that of 87 ISCR1 negative strains. Rate of multiple drug resistance among 17 ISCR1 positive resistant strains was 70.59%,was more than 52.87% of 87 ISCR1 negative strains.4、EA791、K386、EC553、EC1322、EC 1342 had positive result of ESBLs phenotypic confirmatory test. EA291 had positive result of three-dismensional extract test.13 ISCR1 positive resistant strains carried resistant gene:including CTX-M-ESBLs gene 1 group(EA791、K386、EC553),SHV-12(EC1322、EC1342), broad-spectrum beta-lactamase gene TEM-1(EA791、K386、EC553、EC1322、EC1342),DHA type AmpC enzyme gene (EA291), qnrA(EC2394、CF351), qnrB(K1231、EC347、EC1322、EC1342),rmtB(K386),armA(EA1904、K382、K386、EC553、JE982).5. PCR-mapping and DNA sequencing proved that qnrB2 was located downstream of ISCR1 in EC1322、EC1342, qnrA was located downstream of ISCR1 in EC2394、CF351, qnrB6 was located downstream of ISCR1 in K1231、EC347, armA was located downstream of ISCR1 in JE982. Other 10 strains had negative results.Conclusions1. ISCR1 existed in local Enterobacteriacea resistant clinical isolates. ISCR1 positive resistant strains’drug resistant rate of 10 drugs and rate of multiple drug resistant were more than that of ISCR1 negative strains.2. In this study ISCR1 positive resistant strains carried resistant genes which was mediated by plasmid(CTX-M-ESBLs gene 1 group, SHV-12, ampC enzyme gene type DHA, qnrA, qnrB, rmtB, armA). Genotype phenotype of beta-lactamase and aminoglycoside resistant gene was consistent with drug-resistant phenotype. The strains carried gene qnr were not always resistant to quinolone.3. Resistant genes located downstream of ISCR1 most were gene qnr, in rare cases were gene armA. The connect of ISCR1 with the ampC and ESBLs genes were not founded. Infered that ISCR1 may be involved in horizontal spread of quinolone and amino resistant gene in local. Some strains were not founded resistant gene connected with ISCR1, maybe gene context downstream ISCR1 is not suitable for PCR-mapping, needs improve methods to further research.

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