ABSTRACT
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 .