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Objective To investigate the pathogen distribution and drug resistance of gram-negative bacteria causing lower respiratory tract infections in patients with acute exacerbation of chronic obstructive pulmonary disease ( AECOPD) .Methods A total of 742 sputum samples were collected from AECOPD patients with lower respiratory tract infections in Taizhou Hospital of Zhejiang Province during January 2013 and December 2014.Vitek 2 Compact system combined with disk diffusion was used for strains identification and drug susceptibility test.Modified Hodge test and ethylenediamine tetraacetic acid (EDTA) synergic test were used to screen carbapenem-resistant strains.Statistical analysis was performed using WHONET 5.6 and SPSS 20.0 software.Results A total of 593 strains of gram-negative bacteria were isolated , in which 367 strains were nonfermentative bacteria (61.89%), 220 strains were enterobacteriaceae (37.10%), and the rest 6 strains ( 1.01%) were other gram-negative bacteria.Acinetobacter baumannii ( 186 strains ), Pseudomonas aeruginosa (99 strains), Stenotrophomonas maltophilia (33 strains) and Burkholderia cepacia (22 strains ) were top 4 nonfermentative bacteria , and they all showed high resistance to ampicillin , ampicillin/sulbactam, cefazolin, ceftriaxone, cefotetan and nitrofurantoin with resistant rates of 67.20%-100.00%. Drug resistance rates to other β-lactams, fluoroquinolones, aminoglycoside, compound sulfamethoxazole and minocycline were significantly higher in carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa strains than those in non-carbapenem-resistant strains , and the differences were statistically significant (P <0.05 or <0.01).Stenotrophomonas maltophilia and Burkholderia cepacia strains were only sensitive to levofloxacin , compound sulfamethoxazole and minocycline . Klebsiella pneumonia (89 strains), Escherichia coli (80 strains) and Enterobacter cloacae (25 strains) were top 3 enterobacteriaceae , which were almost completely resistant to ampicillin , but were sensitive to piperacillin/tazobactam , cefoperazone/sulbactam , amikacin and carbapenems ( with resistant rates <15%) .More than 50%strains of extended spectrum β-lactamases ( ESBLs )-producing Klebsiella pneumonia and Escherichia coli were moderately or highly resistant to ampicillin/sulbactam , most cephalosporins ( except cefotetan and cefoperazone/sulbactam ), gentamycin, tobramycin, fluoroquinolones, aztreonam, compound sulfamethoxazole and minocycline , and the resistant rates were higher than those in non-ESBLs-producing strains (P <0.05 or <0.01).Conclusions Nonfermentative bacteria and enterobacteriaceae are the most prevalent gram-negative bacterial pathogens in lower respiratory tract infections in patients with AECOPD . Carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa strains, as well as ESBLs-producing Klebsiella pneumonia and Escherichia coli strains are highly resistant to most antibacterial agents .
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Objective To investigate drug resistance and carbapenemase genotypes of carbapenemresistant Acinetobacter baumannii.Methods A total of 75 clinical isolated strains of carbapenem-resistant Acinetobacter baumannii were collected from Taizhou Hospital in Zhejiang province during January 2011 and June 2012.Vitek 2 Compact microbial identification system was used for bacterial identification and drug susceptibility test,and modified Hodge test was used to screen strains producing carbapenemases.Genotypes of carbapenamases were determined by polymerase chain reaction.Results All 75 carbapenem-resistant Acinetobacter baumannii strains were resistant to most antibacterial agents except amikacin.The resistant rate to amikacin was 13.3％ (10/75).OXA-23 gene was positive in 69 strains (92.0％),and OXA-51 gene was positive in 67 strains (89.3％).No IMP,VIM and SIM gene was observed.Conclusion OXA enzyme is the main cause of drug resistance in this group of carbapenem-resistant Acinetobacter baumannii,and OXA-23 and OXA-51 genes are the most popular carbapenemnases coding genes.