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Objective To study the molecular characteristic of the epidemic plasmids carrying blaCTX-M-15 in Guangzhou. Methods A total of 38 strains of E. coli and 47 strains of K. pneumoniae both producing CTX-M-15 ESBLs were collected from nine hospitals in Guangzhou from 2007 to 2008. The clonal relationship of isolates carrying blaCTX-M-15 was determined by PFGE and MLST. Antimicrobial susceptibility was determined by microdilution test for all isolates. Conjugative plasmids carrying blaCTX-M-15 were obtained by mating and were subject to restriction analysis. PCR was used to determine phylogenetic groups of E. coli,and to study replicon type and the genetic contexts of the plasmids harboring blaCTX-M-15. Serum agglutination test was used to detect the serotype of E. coli. Results The 37 strains of E. coli were classified into 28 genotypes, while the 47 strains of K. pneumoniae were divided into 30 genotypes. ST131 was found in E. coli but not O25 serotype. Two novel-alleles of tonB and new ST were determined in K. pneumoniae. Forty out of 58 isolates represented independent genotypes have been succeeded to transfer the plasmid carrying blaCTX-M-15 to the E. coli C600(Rif) by conjugation. The sizes of plasmids carrying blaCTX-M-15 are 65 kb in 57.9% isolates of E. coli and 92 kb in 87.5% isolates of K. pneumoniae. Two epidemic plasmids were detected in E.coli and K. pneumoniae by restriction enzyme, designated p15-e and p15-k respectively. The blaCTX-M-15 and ISEcpI were identified on p15-e, and the blaCTX-M-15 ,ISEcpI,aac(6')- Ⅰ b,aac(3')-Ⅲ ,blaOXA-1 ,qnrB,qnrS,blaDHA-1 , blaTEM-1 were determined on p15-k. The p15-k also was identified to belong to the incompatible group FⅡ. Conclusion The local dissemination of blaCTX-M-15 appears to be due to the spread of epidemic plasmids harboring blaCTX-M-15. No evidence supports the dissemination of clone strains which carried blaCTX-M-15.
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Objective To investigate the impact on the resistance of carbapenem with the expression of OprD2 or OprD2 mutation in Pseudomonas aeruginosa. Methods One hundred and one clinical strains of Pseudomonas aeruginosa with MIC for imipenem ≥8 μg/ml were studied. MIC were determined by the broth microdilution method, and the antibiotics tested were imipenem(IPM ), biapenem( BPM), meropenem(MEM) and panipenem(PEM). The expression of the oprD2 gene in Pseudomonas aeruginosa were analyzed by real-time reverse transcriptase PCR(RT-PCR). For the Pseudomonas aeruginosa with normal expression of OprD2 and resistance to imipenem, full-length oprD2 gene was amplified by PCR and the products were sequenced. Results According to the result of the expression of oprD2 gene, 101 strains of Pseudomonas aeruginosa were divided into two groups: group1 with diminished expression of OprD2, and group2 with normal expression of OprD2. Comparing isolates with MIC of 4 kinds of carbepenem agents ≥ 16 μg/ml in two groups. Data showed the amount of OprD2 expression were different between two groups(P ＜0.01 or P ＜ 0.05). In group1, there are 28 isolates with MIC ≥ 16 μg/ml of all the 4 kinds of carbapenems, among which 25 isolates have obviously diminished expression of OprD2 ( ＜ 0.4). Negative correlations tendency appeared between the level of OprD2 transcription and MICs of 4 kinds of carbepenem agents in Pseudomonas aeruginosa. In group2, 16 strains with OprD2 mutation divided into 4 types according to the pattern of alteration. Compared with PAO1, these strains have increased MIC with different degree to IPM,BPM, MEM and PEM. Conclusion The deletion or diminished expression of OprD2 resulted in resistance to imipenem in Pseudomonas aeruginosa. The level of OprD2 transcription and antimicrobial activities for carbapenem agents proved to be highly correlated in Pseudomonas aeruginosa. The mutation of OprD2 in Pseudomonas aeruginosa probably decreased the sensitivity of carbapenem agents against Pseudomonas aeruginosa.
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Objective To study phylogenies, epidemiology and genetic environment of CTX-M type of ESBLs produced by Escherichia coli and Klebsiella pneumoniae isolated from nine hospitals in Guangzhou. Methods The phylogenies of CTX-M type of ESBLs were analyzed by PCR Genetic environment of CTX-M-15 encoding gene (bla_(CTX-M-15)) were investigated by conjugation test and plasmid analysis. The clonal relationship of strains producing CTX-M-15 was determined by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Results A total of 361 ESBLs-producing isolates of Escherichia coli and Klebsiella pneumoniae were collected. 67.3% of ESBLs strains were detected to produce CTX-M-type ESBLs, and the commonest genotypes in Escherichia coli and Klebsiella pneumoniae were CTX-M-14 (35.4% and 28.3%), CTX-M-15(21.5% and 26.1%) EBIC-PCR products of all CTX-M-15-producing strains show 39 strains of Escherichia coli were classified into 27 genotypes while 43 strains of Klebsiella pneumoniae were divided into 30 genotypes. Furthermore, the genotypes of CTX-M-55, CTX-M-19, CTX-M-27, with ceftazidime-hydrelyzing activity, were detected in this study. The great majority of bla_(CTX-M-15) genes were found to locate on a 65 000 bp-conjugative plasmid, and there was no blaTEM-1, bla_(OXA-1), blaDSA-1 or aac (6')-Ib-cr gene coexisted on the plasmid, ISEcp1-like insertion sequences, relative to mobilization of bla_(CTX-M-15) gene, were detected in all bla_(CTX-M-15) positive strains, and the distances between the end of ISEcp1-like insertion sequences and the start cedon of bla_(CTX-M-15) were equal, with 48 base pairs. Conclusion CTX-M-14 is still the most common genotype of ESBLs in Guangzhou, but high prevalence of CTX-M-15 ESBLs hydrolyzing ceftazidime already appears in south China.
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Objective To analyze a potential outbreak mechanism 0f Pseudomonas eruginosa by investigating the homology of pan-drug resistance isolates(PDR)isolated in four hospitals of Guangzhou from March 2005 to March 2007.Methods The pulse-field gel lectrophoresis(PFGE)was used to detectl34 strains of pan-drug resistant Pseudomonas eruginosa in four hospitals,and determined whether they were derived from the same clone.Results 1 34 strains were classified into 56 types based on PFGE pattern. Type A Was the commonest clone among four hospitals,45 strains belonged to type A,mainly spreaded in hospital A. The rest strains were identified:7 for type B,6 for type C,6 for type D,which were isolated from hospital B to hospital D,respectively.There were 40 strains classified for individual types.General comparison showed there Was no a large clone existing in all four hospitals,though type Q clone appeared in hospital B and hospital D.One strain from hospital B and one strain from hospital C had 80%homology with type A from hospital A.The environment survey showed there was no clonal strain of type A found in hospital A,although various samples from respiratory therapy equipment,bronchoscopes and medical erosols were collected and cultivated for three times during the period.However,six patients arrying type A Pseudomonas aeruginosa had been admitted to the same ICU of hospital A for many times.Analysis of antimicrobial resistance of the common clone from four hospitals revealed that 42 of 43 type A of Pseudomonas aernginosa produced IMP-9 metallo β-lactamase.The strains of type B,type C and type D didn't produced metallo B. 1actamase.Conclusions The various degree of clonal spread of pan-drug resistance Pseudomonas aeruginosa had occurred in four hospitals individually in two years.There Was also clonal spread among some hospitals. It is important to monitor the patients colonized with epidemic clones to prevent clonal spread.
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BACKGROUND: The degree of neurofilament (NF) phosphorylation is closely correlated with the occurrence of Alzheimer disease (AD), and apolipoprotein E4 (apoE4) is a generally acknowledged liability factor for AD, but the effect and mechanism of apoE4 on the NF phosphorylation in neurons are not very clear. It has been reported that in the neurons cultured in vitro and in brain tissue of AD patients, the amino acid residues of apoE4 protein C terminal (272-299) could be truncated by hydrolysis,and produce truncated-apoE4 fragment. The latter interacts with the NF phosphorylation in neurofibrillary tangles (NFTs), which are the characteristic pathological changes of AD.OBJECTIVE: To observe the effect of truncated-apoE4 overexpression on the NF phosphorylation in the cultured neurons.DESIGN: A non-randomized controlled observation.SETTING: Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tongji Medical College, Huazhong University of Science and Technology.MATERIALS: The experiment was carried out in the Laboratory of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology in December 2005. The mice neuroma cell strain N2a was provided by Dr. Xu.METHODS: The truncated-apoE4(△272-299) cDNA was subcloned into pEGFP-c3 to form pEGFP-T-apoE4 recombinant. Then pEGFP-c3, pEGFP-apoE4 and pEGFP-T-apoE4 were transfected into N2a cells by lipofectamine2000 respectively. NF phosphorylation was detected by Western blot assay. The activities of glycogen synthase kinase-3 (GSK-3) and cyclin-dependent kinase 5(CDK-5) were measured.MAIN OUTCOME MEASURES: The degree of NF phosphorylation and the activities of GSK-3 and CDK-5 were mainly observed.RESULTS: In the transfected groups, the contents of phosphorylated NF were significantly increased, the GSK-3 activities were significantly increased, which were the most significant in the pEGFP-T-apoE4 transfected group (P＜0.05), but the CDK-5 activities were not significantly different from that in th e control group (P＞0.05).CONCLUSION: These results indicate that in vitro overexpression of truncated-apoE4(△272-299) can lead to NF hyperphosphorylation by activating of GSK-3 but not CDK-5, which may be the underline mechanism of AD induced by truncated-apoE4(△272-299).