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Objective:To investigate the resistance and transmission mechanism of carbapenem-resistant Enterobacterales (CRE), so as to provide the scientific evidence for the treatment and prevention of CRE infection.Methods:Seventy-six isolates of CRE isolated from Shaoxing Second Hospital between May 2016 and August 2018 were included. The isolates were re-identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The minimum inhibitory concentrations (MICs) of colistin, tigecycline, ceftazidime-avibactam, fosfomycin and other antibacterial drugs were determined using broth microdilution or agar dilution methods. PCR and sequencing analysis were performed to detect carbapenemase encoding genes ( blaKPC, blaNDM, blaIMP, blaVIM, blaOXA-48). Pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to analyze homology of strains. S1-PFGE combined with Southern blot hybridization were used to locate the carbapenamase genes. Filter mating test were performed to determine the horizontal transfer ability of plasmids harboring carbapenamase genes. Results:Among the 76 isolates of CRE, 51 isolates were Klebsiella pneumoniae; 10 isolates were Escherichia coli; 15 isolates were other Enterobacterales. The 76 CREs were mainly isolated from urine, sputum and blood samples. The distribution rate of ICU was the highest (55.26%). The 76 CREs showed low resistance rates (0%, 1.33%, 18.42%) to colistin, tigecycline and ceftazidime-avibactam. The resistance rates to amikacin and fosfomycin were <45%, and the resistance rates to other drugs were >97%. The detection rate of KPC-2 carbapenemase was the highest (85.33%). The ST11 CRKP producing KPC-2 carbapenemase accounted for the highest proportion (62.75%), mainly distributed in the ICU (62.50%). Southern blot hybridization showed that blaKPC-2 was mainly located on a plasmid about 90 kb (39/63). Filter mating test showed that blaKPC, blaNDM and blaIMP could be transferred horizontally to recipient bacteria through plasmids. Conclusions:The 76 CRE isolates were only susceptible to a few antibacterial drugs, such as colistin, tigecycline and ceftazidime-avibactam. The production of KPC-2 carbapenemase was the main reason for the resistance of Enterobacterales to carbapenems. KPC-2 carbapenemase-producing ST11 Klebsiella pneumoniae was the main epidemic clone of carbapenem-resistant Klebsiella pneumoniae (CRKP). The 90 kb size plasmid was the main plasmid encoding blaKPC-2 gene. Carbapenemase genes can be transferred horizontally through plasmids. The hospital should strengthen prevention of nosocomial infections to control the clonal prevalence of CRE.
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Objective To compare the antibacterial activity in vitro of Haizhengmeite and Mepem. Methods Four hundreds and eighteen bacteria isolated were collected from clinical settings in different area,including 104 strains of Escherichia coli(52 strains of ESBLs +and 52 strains of ESBLs -), 104 strains of Klebsiella pneumonia(52 strains of ESBLs +and 52 strains of ESBLs -),56 strains of Proteus spp. (28 strains of ESBLs +and 28 strains of ESBLs -), 52 strains of other Enterobacteriaceae, 51 strains of Acinetobacter baumanii and 51 strains of Pseudomonas aeruginosa.Two pharmaceutical products of meropenem injection were Mepem from Japan Sumitomo Pharmaceuticals Co., Ltd and Haizhengmeite from Zhejiang Haizheng Pfizer pharmaceuticals Co.Ltd in China, respectively.Minimum inhibitory concentrations(MIC)of two products of meropenem were determined by broth microdilution method and agar dilution method according to the Clinical and Laboratory Standards Institute(CLSI,2016).Results The sensitive rates of Escherichia coli, Klebsiella pneumoniae, and Proteus spp.to Haizhengmeite and Mepem were >85%,while the rates of the sensitivity to Acinetobacter baumanii and Pseudomonas aeruginosa were lower,with the rates of 33.3%,31.4% and 58.8%,52.9%,respectively.Conclusions Haizhengmeite and Mepem both show good antibacterial activity against Enterobacteriaceae, but lower activity against Acinetobacter baumanii and Pseudomonas aeruginosa.Both products are stable to ESBLs,and no significant difference is observed between the two products in antibacterial activity in vitro.
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Objective@#To examine the expression of naked cuticle homolog 2 (Nkd2) in the process of root development and osteogenic differentiation of dental follicle cells of rat (rDFC), in order to explore the molecular mechanisms of Nkd2 on the osteoblast differentiation of rDFCs.@*Methods@#Immunohistochemical analysis was used to detect the expression of Nkd2 in the base dental follicle of the mandibular first molar of rat at 1, 3, 5, 7, 9, 11 and 13 days postnatal. Mineralization nodule formation of rDFCs was detected by alizarin red staining and cetylpyridine. The change of Nkd2 during osteogenic differentiation of rDFCs was evaluated by Western blotting and the associations between Nkd2 and osteogenic cytokines of alkaline phosphatase (ALP), Runt-related transcription factor-2 (RUNX2) and osteocalcin (OCN) were examined. The rDFCs were transfected with small interfering RNA (siRNA) to knock down the expression of Nkd2 and Western blotting and quantitative real-time PCR (qPCR) were adopted to explore the effects of Nkd2 on osteogenic differentiation by detecting variations of Nkd2 and osteogenic factors ALP, RUNX2, OCN among silencing group (Si), negative control RNA group (Nc) and mock control group (Mock), respectively.@*Results@#The expression of Nkd2 in the base dental follicle of the mandibular first molar of rat was time dependent. Mineralization nodules of rDFCs and absorbance of cetylpyridine after osteogenic induction increased gradually (the absorbances of cetylpyridine were 0 week: 0.017±0.005, 1 week: 0.702±0.044, 2 weeks: 1.812±0.531, 3 weeks: 2.767±0.253, respectively). Results of Western blotting showed that Nkd2 (1.60±0.23) of mineralization group was significantly higher than that of control group (1) (P<0.05) at the early stage of osteogenic differentiation along with the expression of other osteogenic factors. The protein and mRNA of Nkd2 and osteogenic factors were significantly decreased in Si group compared with Nc and Mock groups (P<0.05), and no changes between Nc and Mock groups were observed. The changes of protein in Si, Nc and Mock groups were Nkd2: 0.42±0.10, 1.12±0.07, 1, ALP: 0.70±0.15, 1.11±0.14, 1, RUNX2: 0.58±0.08, 0.93±0.08, 1 and OCN: 0.64±0.06, 0.99±0.02, 1, respectively. The mRNA variances in Si, Nc and Mock groups were Nkd2: 0.39±0.05, 0.96±0.10, 1, ALP: 0.15±0.13, 1.01±0.07, 1, RUNX2: 0.39±0.31, 0.97±0.13, 1, OCN: 0.17±0.08, 1.08±0.21, 1, respectively.@*Conclusions@#Nkd2 participates in the root development process in rat and may acts as a positive role in the early stage of osteogenic differentiation of rDFCs in rat.
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Objective To investigate the prevalence of colistin resistance and mcr-1 gene in pa-tients with bloodstream infection caused by Escherichia coli (E.coli) and Klebsiella pneumoniae (K.pneu-moniae) in Zhejiang Province. Methods A total of 869 clinical strains of the Enterobacteriaceae family, including 611 E.coli and 258 K.pneumonia strains, were isolated from patients with bloodstream infection (BSI) in Zhejiang Province from March 2014 to April 2015. Broth microdilution method and PCR were re-spectively performed to detect colistin resistance and mcr-1 gene in those stains. Susceptibilities of mcr-1-positive strains to other antibiotics were assessed by E-test. Pulsed-field gel electrophoresis(PFGE) and multilocus sequence typing(MLST) were used for molecular typing. Location of mcr-1 gene was determined by analysis of PFGE profiles of S1-digested genomic DNA and Southern blot hybridization. Plasmid transfer to E.coli recipients was investigated using filter mating test. Clinical data of the patients infected with mcr-1-positive strains was collected and analyzed. Results The minimum inhibitory concentration (MIC) values of colistin to the 869 Enterobacteriaceae strains ranged from ≤0.06 μg/ml to 16 μg/ml. Six (0.69%) E.coli strains were identified to be colistin-resistant and mcr-1-positive and the MIC values against them ranged from 8 μg/ml to 16 μg/ml. No colistin-resistant or mcr-1-positive K.pneumonia strain was identified. All mcr-1-positive strains were susceptible to carbapenems and most of them(83.33%,5/6) were suscepti-ble to tigecycline and β-lactamase inhibitor combinations tested in this study. The six mcr-1-positive strains were of different sequence types (STs) and the mcr-1 genes carried by them located on three types of plas-mids with the sizes of 33 kb,61 kb and 244.4 kb. Conclusion The prevalence of mcr-1 gene in E.coli and K.pneumonia strains isolated from patients with BSI in Zhejiang Province was relatively low, only ac-counting for 0.69% of all isolated Enterobacteriaceae strains.Those strains carrying mcr-1 gene showed low drug resistance to colistin. The mcr-1-positive strains were usually non-pathogenic clones and remained sus-ceptible to many antimicrobial agents, which was conducive to favorable outcomes. In order to clarify the clinical impact of this novel resistance gene on public health,further studies should be conducted.
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Objective To study the epidemiology and genotypes of extended-spectrum beta-lactamases (ESBL)-producing Escherichia coli (EC) and Klebsiella pneumoniae (KP) that caused community-onset bloodstream infections (COBSI) in 9 county hospitals of Zhejiang Province.Methods This is a multi-center, prospective, observational study.The cases and isolates with COBSI caused by EC and KP were consecutively collected from 9 county hospitals in Zhejiang Province between 1st March 2014 and 30th April 2015.The double disk diffusion method was used to confirm the production of ESBL.The ESBL genotypes were determined by polymerase chain reaction(PCR) amplification and sequence analysis.Multi-locus Sequence Typing (MLST) was used to analyze the homology of ESBL-producing isolates.Minimal inhibitory concentration (MIC) of frequently used drugs for ESBL-producing isolates was determined by in-vitro antimicrobial susceptibility tests.Results During the study period, a total of 172 cases with COBSI were collected and 171 cases were eligible, among which 126 were caused by EC and 45 were caused by KP.The overall prevalence of ESBL was 34.5% (59/171),and the prevalence of ESBL-EC and-KP was 41.3% (52/126) and 15.6% (7/45), respectively.CTX-M-type ESBL accounted for 96.6% (57/59) of all the ESBLs-producing isolates, and the most common type was CTX-M-14 (27.1%, 16/59), followed by CTX-M-55 (22%, 13/59).MLST analyses revealed significant genetic diversity among ESBL-EC and-KP.The most prevalent ST of ESBL-EC was ST131 (23.1%).In addition to carbapenems, cefoperazone/sulbactam, piperacillin/tazobactam, moxalactam, amikacin and fosfomycin also showed good in-vitro activity against ESBL-EC and-KP.Conclusions The prevalence of ESBL in EC and KP is high in 9 county hospitals of Zhejiang Province, and the most common genotypes are CTX-M-14 and CTX-M-55.The detection rate of ESBL in EC is higher than in KP.It could be considered adequate empirical therapy according to the results of antimicrobial susceptibility tests.Carbapenems, cefoperazone/sulbactam, piperacillin/tazobactam, moxalactam, amikacin and fosfomycin have good in-vitro activity against ESBL-EC and-KP.