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Min-jun Chen

Publications and source records attributed to Min-jun Chen.

9 recordsLinked to original sources
PubMed2006

[Molecular mechanism of multiple-drug and pan-drug resistance among Acinetobacter species].

OBJECTIVE: To investigate the molecular mechanism of multiple-drug and pan-drug resistance among Acinetobacter species. METHODS: Non-repetitive 90 carbapenem-resistant strains of Acinetobacter species were collected in Beijing, Guangzhou, and Fuzhou 1999-2004. The homology of the isolates was determined by both pulsed field gel electrophoresis and randomly amplified polymorphic DNA typing. Seven representative clones were selected from the 90 strains of Acinetobacter isolated from different hospitals to be used for further study. Analytical isoelectric focusing was used to measure the isoelectric point of the beta-lactamase. Plasmid DNA was extracted and purified Genes of different beta-lactamase, including bla(TEM--), bla(SHV-), bla(PER-), blaI(MP-), bla(VIM-), and bla(OXA-) genes, in these clone strains were amplified and sequenced. PCR was used to analyze the integrons. RESULTS: The P clone strain isolated during an outbreak of pan-drug-resistant Acinetobacter species in Peking Union Medical College Hospital 2004 was not susceptible to most common antimicrobial agents tested. The 7 representative clones produced multiple beta-lactamases: TEM-1, high-level AmpC, SHV-type, OXA-23 carbapenemase and IMP-8 and metalloenzyme respectively. One clone produced PER-1 enzyme. These 7 clone strains were resistant to most beta-lactams (including carbapenems), erythromycin, chloramphenicol, and rifampin. Two clone strains were susceptible to cefoperazone/sulbactam and amikacin while 4 clone strains susceptible to levofloxacin. All of the 7 clones were susceptible to minocycline and colistin. Five different integrons were found, harboring the genes mediating the resistance to aminoglycosides, rifampin, chloramphenicol, and carbapenems (bla(IMP-8)). CONCLUSION: The molecular bases of multiple-drug or pan-drug resistance in Acinetobacter species include production of OXA-23 carbapenemase or IMP type metalloenzyme and integrons with different resistance gene cassettes. Pan-drug-resistant Acinetobacter species are susceptible to old antimicrobials agents, such as colistin and minocycline.

Acinetobacter↗
PubMed2006

[A multicentre study on the pathogenic agents in 665 adult patients with community-acquired pneumonia in cities of China].

OBJECTIVE: To investigate the pathogenic causes of community-acquired pneumonia (CAP) in adult patients in China, the relation of previous antibiotic use and the Pneumonia Patient Outcome Research Team (PORT) classification to microbial etiology, and the prevalence of drug resistance of common CAP bacteria. METHODS: A prospective study was performed on 665 consecutive adult patients with CAP at 12 centers in 7 Chinese cities during one year. The etiology of pneumonia was considered if one of the following criteria was met: (1) valid sputum sample yielding one or more predominant strains; (2) blood cultures yielding a bacterial pathogen; (3) seroconversion, a > or = 4-fold increase or decrease titers of antibodies to Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella pneumophila. Minimum inhibitory concentration (MIC) of respiratory tract isolates was determined using the agar dilution method. RESULTS: Pathogens were identified in 324/610 patients (53.1%) with valid serum samples and sputum cultures as follows: Mycoplasma pneumoniae (126, 20.7%), Streptococcus pneumoniae (63, 10.3%), Haemophilus influenzae (56, 9.2%), Chlamydia pneumoniae (40, 6.6%), Klebsiella pneumoniae (37, 6.1%), Legionella pneumophila (31, 5.1%), Staphylococcus aureus (23, 3.8%), Escherichia coli (10, 1.6%), Moraxella catarrhalis (8, 1.3%), Pseudomonas aeruginosa (6, 1.0%). Of 195 patients with a bacterial pathogen, an atypical pathogen was identified in 62 (10.2%) cases. The non-susceptibility rate of Streptococcus pneumoniae to penicillin, azithromycin, and moxifloxacin was 20.3%, 75.4% and 4.3% respectively. CONCLUSIONS: Atypical pathogens have important role in CAP, with Mycoplasma pneumoniae being the most common pathogen, and mixed infection of atypical pathogens with bacteria was found in 10.2% of the cases. Streptococcus pneumoniae and Haemophilus influenzae remain the most important bacteria for CAP. More than 75.0% of Streptococcus pneumoniae was resistant to macrolides and 20.3% was resistant to penicillin.

Adult↗
PubMed2006

[Application of metabonomics in complicated theory system research of traditional Chinese medicine].

Metabonomics, a new and rapid-developing technology, will be powerful means to the research of complexed theory system and modernization of traditional Chinese medicine (TCM). Discovery of biomarkers and analysis of common properties from the metabolome of a specific TCM syndrome will facilitate the modernized study of TCM system, promote the quantitative and scientific elucidation of TCM syndrome differentiation, provide an in-depth understanding of the TCM theory of Zang-xiang, help predict the disease on-set, and achieve a comprehensive evaluation of systemic clinical efficacy, safety and mechanism of action of the TCM combination formulas along with a better understanding of intestinal microflora ecology. The new approach with combined metabonomics and TCM methodologies will provide a new pathway and methodology for the study of complicated theory system of TCM and its modernization.

Biomarkers↗
PubMed2004

[Resistance surveillance of common community respiratory pathogens isolated in China, 2002 - 2003].

OBJECTIVE: To investigate antimicrobial resistance of common community respiratory pathogens isolated in China, 2002 - 2003. METHODS: 779 strains of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Group A beta-haemolytic Streptococci and oxacillin-susceptible Staphylococcus aureus (MSSA) were isolated from patients with community-acquired respiratory tract infections at 5 hospitals in China from April 2002 to 2003. Meanwhile, 185 strains of S. pneumoniae, H. influenzae and M. catarrhalis were isolated from nasopharynx swabs at 2 day-care centers in Beijing. Agar dilution method was used to determine the minimal inhibitory concentration (MICs) of cefprozil and other 9 antibiotics against these strains. RESULTS: The prevalence of penicillin-intermediate S. pneumoniae (PISP) was 23.9% and that of penicillin-resistant S. pneumoniae (PRSP) was 22.7% at 5 cities in China. The prevalence of PISP were 44.1% in Hangzhou, 26.2% in Wuhan, 21.5% in Shenyang, 20.8% in Shanghai, 18.5% in Beijing, and 12.7% at day-care centers in Beijing;the prevalance of PRSP were 34.9% in day-care centers, 31.9% in Shanghai, 27.9% in Wuhan, 22.1% in Hangzhou, 13.8% in Shenyang and 8.6% in Beijing. The susceptible rate of levofloxacin in S. pneumoniae was 96.3%. 9.5% of H. influenzae and 87.4% of M. catarrhalis produced beta-lactamases. The susceptibility of amoxicillin/clavulanate, cefaclor, cefprozil, cefuroxime, ceftriaxone, azithromycin, and levofloxain in these two species ranged from 96.4% to 100%. The resistance rate of azithromycin in S. pneumoniae was higher than 60%. Cefprozil MICs against PISP, Group A beta-haemolytic Streptococci and MSSA were 4 - 16 fold lower than cefaclor. CONCLUSIONS: Antimicrobial resistance in respiratory pathogens, especially S. pneumoniae is increasing. It brings concerns that high macrolide resistance was found in gram-positive cocci. Cefprozil was more active than cefaclor against respiratory pathogens.

Anti-Bacterial Agents↗
PubMed2004

[Plasmid-mediated cephalosporinase among extended-spectrum-beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae].

OBJECTIVE: To investigate the prevalence and genotype of plasmid-mediated cephalosporinase (AmpC) beta-lactamase in extended-spectrum-beta-lactamase-producing (ESBL) Escherichia coli and Klebsiella pneumoniae. METHODS: 24 strains of cefoxitin-resistant ESBL-producing E. coli and 8 strains of K. pneumoniae were collected from January to December 2001 at Beijing Chaoyang Hospital. Analytical isoelectric focusing electrophoresis was used to measure the pI of the beta-lactamase. Conjugation experiment was used to study the transfer of cefoxitin resistance. The homology of the isolates was determined by pulsed field gel electrophoresis (PFGE). Plasmid-mediated AmpC enzyme genes were amplified and sequenced by using multiplex PCR. RESULTS: The prevalence of ESBL-producing E. coli and K. pneumoniae were 16.8% (49/292) and 16.5% (35/212), respectively. The prevalence of AmpC enzyme among ESBL-producing E. coli and K. pneumoniae isolates were 2.0% (1/49) and 17.1% (6/35), respectively. These 7 isolates produced DHA-1 AmpC enzyme. One strain of K. pneumoniae could transfer cefoxitin resistance to the recipient. Among 7strains, 5 strains produced CTX-M-3 and 2 produced SHV-12 ESBL. These 7 strains also produced TEM-1 broad-spectrum enzymes. These strains harbored 2 - 5 plasmids and one of them were 33 - 36 kb. PFGE showed these strains came from a variety of clones. CONCLUSIONS: In this hospital, 7 strains of the ESBL-positive E. coli and K. pneumoniae produced both DHA-1AmpC enzyme and CTX-M-3/SHV-12 ESBL. These 7 strains were from different clones.

Anti-Bacterial Agents↗
PubMed2003

[Mechanism of carbapenems resistance in Acinetobacter baumannii].

OBJECTIVE: To investigate the mechanism of carbapenems resistance in Acinetobacter baumannii. METHODS: WHONET-5 software was used to analyze the trend of carbapenem resistance in Acinetobacter baumannii collected from 1999 to 2001 at Peking Union Medical College Hospital. Analytical isoelectric focusing was used to measure the pI of the beta-lactamase. Conjugation experiment was used to study the transfer of carbapenem resistance and plasmid DNA was extracted and purified with Qiagen Plasmid Mini Kit. The homology of the isolates was determined by pulsed field gel electrophoresis (PFGE). Integrase genes and blaIMP-, blaVIM-, blaOXA- genes for resistant isolates were amplified and sequenced. RESULTS: Imipenem resistance in A. baumannii was ranged from 1.8%-8.5%, but only 9 resistant isolates were viable. They were co-resistant to other carbapenems, ceftazidime, aztreonam, and gentamicin, and four isolates were resistant to ciprofloxacin. Impipenem resistance could not be transferred to susceptible strains. No plasmid was extracted. Each isolate produced TEM-1, AmpC, and two enzymes (pI 6.7, 6.0), which can not be inhibited by cloxacillin and clavulanic acid. Each isolate had class I intergase gene. Nine isolates were all negative for PCR of blaIMP- and blaVIM- genes, but positive for blaOXA-23 specific PCR. Sequencing found 100% homology with blaOXA-23. PFGE found 3 clones (A type: 5 isolates; B type: 3 isolates; C type: 1 isolate). Control isolates (imipenem-susceptible, but ceftazidime, ciprofloxacin, and gentamicin resistant) were also A clone. CONCLUSIONS: Production of OXA-23 carbapenemase in A. baumannii was one of the main mechanisms of carbapenems resistance at our hospital. It brings concern that imipenem-resistant clone has evoluted from nosocomial multiple-resistant strains.

Acinetobacter baumannii↗
PubMed2003

[Identification of the habitat of Ligusticum chuangxiong with chromatographic fingerprinting].

OBJECTIVE: To establish the chromatographic fingerprinting for identifying the habitat of Ligusticum chuangxiong. METHOD: HPLC system was applied to obtain the chromatograms of L. chuangxiong samples from different areas, and 15 peaks were measured from the chromatograms. Then some computer-based methods including principle component analysis, clustering analysis, similarity calculation and fisher factor analysis were applied for data analysis. RESULT: There was obvious difference among chromatographic fingerprints of L. chuangxiong samples from different areas. The 15 measured peaks could be used as the fingerprint features. CONCLUSION: Chromatographic fingerprinting can be used for identifying the habitat of L. chuangxiong.

China↗