ABSTRACT
Objective The primary goal of this work is to discuss the molecular mechanism of multi-drug resistant Pseudomonas spp. resistance to carbapenam and aminoglycoside antibiotics. Methods From June 2012 to March 2013, six strains of P. aeruginosa and P. putida producing carbapenemasefrom 4 different district were collected. Species identification was performed using VITEK-2 compact system and by sequencing of 16S rDNA amplicons. Minimum inhibitory concentrations were determined by E-test method. Production of carbapenemase were detected by Carba NP method. Carbapenemase genes and aminoglycoside 16s rRNAmethylase genes were screened by PCR, and their subtypes combined with their immediate genetic context were worked out by assemble the sequence of overlapped PCR amplicons. SpeI-PFGE (Pulse field gel electrophoresis after SpeI enzyme digestion) were conducted to evaluate their clonal relatedness. S1-PFGE (Pulse field gel electrophoresis after S1 enzyme digestion) were conducted to conform the relatedness of plasmids they carried. Results Three multidrug resistant P. aeruginosa and three P. putida, were all positive for Carba NP test and conformed producing class B carbapenemase. PCR screening followed by sequencing confirmed carriage of blaIMP-45 and armA, which confer resistance to β-lactams (except aztreonam) and aminoglycosides. These two genes co-located in a Tn1548-associatedregion. SpeI-PFGE disclosed that these isolates were not clonal closely related to each other, except two P. aeruginosa isolates were clonal related. S1-PFGE results showed that these isolates all carried plasmids of large size (300-600 kb). Conclusions This study showed that Pseudomonas spp. isolates co-carried blaIMP-45 and armA were disseminated in clinical settings. Spread of these genes may attribute to horizontal gene transfer of related entities.
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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 explore distribution and genetypes of plasmid-mediated quionlone resistance genes qnrA.qnrB and qnrS in Enterobacteriaceae isolates iu Renmin Hospital of Wuhan University.Methods The qnrA,qnrB and qnrS genes in Enterobaeteriaceae isolates including nonrepetitive 129 isolates of E.coli.13 isolates of E.cloacae and 37 isolates of k pneunoniae were detected by PCR.Antibiotic suseeptibility testing for 15 antibiotics were also performed by K.B in virto.MICs of ciprofloxacin were determined by agar dilution methed.Plasmid conjugatable test wag applied to examine whether qnrA,qnrB and qnrS genes were located in conjugatable plasmid.For qnr-positive strains,integrase I and SHV-1,TEM-1,CTX-M,OXA-I,OXA-Ⅱ,OXA-Ⅲ,DHA and EBC β-lactamases genes were examined.Results 25 qnr-positive isolates were detected among 179 Enterobaeteriaceae isolates,including 6 qnrA-positive isolates,9 qnrB-positive isolates and 10 qnrS-positive isolates,which were presented in 3.35%.5.02%,and 5.59%respectively.All positive isolates were susceptible to imipenem but resistance to some other drugs.2 qnrA-positive isolates and 4 qnrB-positive isolates of them were susceptible to Quinolones.The plasmid wag eonjugatable in 2 qnrA-positive isolates and 4 isolates carrrying qnrB and qnrS.23 qnrA-positive isolates harbored type 1 Integrase,but one isolate with both qnrB and qnrS did not carry Type 1 Integrage.14 isolates of them were TEM-1 producing strains.6 isolates were OXA-Ⅲ-producing strains.and 7 isolates of them were EBC-producing strains.Conciusions In HuBei province,a low prevalence of qnrA,qnrB and qnrS wag determined in Enterebacteriaceae isolates.Muhidrng-resistance was found in qnr-pesitive isolates and qnr genes were detected in quinolone susceptible strains.Extendedspectrum β-lactamages could be presented in qnr-positive isolates too.