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Active monitoring of the drug resistance pattern of IntegronI

CHEN Dan-hua,ZHANG Ru-lin,DING Xing,et al. (Department of Clinical Laboratory,First Affiliated Hospital of Shanghai Communication Hospital,Shanghai 200080,China)  
Objective To monitor the integronI and gene cassettes at the bacterial DNA by using the bacteria Pseudomonas aeruginosa,which infected repeatedly the patient at the respiratory tract,who didn't recover although being treated medicaly in the hospital for a long time,and to analyze the resistant pattern and mechanisms of this bacteria combined with clinical history and symptoms.These bacteria Pseudomonas aeruginosa has developed resistances against the regularly standard antibiotics from the whole susceptibility to the partial one and till to all resistance.Methods To identify the bacteria with VITEKⅡ,KB-Agar Diffusion Test for antibiotic susceptibility tests,DNA and plasmid extraction and purification kits for bacterial DNA and plasmid extraction, to amplify and integronI by using PCR while to detect gene cassettes in variable region of integronI by LA PCR,Agarose electrophoresis of PCR and LA-PCR products,DNA sequencing by Firma Invitrogen and analyzed by Gen-Bank Data base of BLAST,and analyze the resistance pattern combined with the clinical history and symptoms of the patient.Results There exists integronl at the Pseudomonosa before and after becoming resistant.Gene cassettes includingβ-lactamase cassettes and CatB8、aad4 and aac(6′)-Ib cassettes could not detect all the antibiotics during susceptible period.Several gene cassettes could be detected during the antibiotic multi-resistant period.They are resistant toβ-lactam(cephalosporins) chloramphenicols,aminoglycosides and aminoglycoside -quinolones antibiotics respectively.Surprisingly,we have also detected the cassettes of MexR-OprD system.It means that the integronl can not only actively take gene cassettes for antibiotic resistance,but also can take and express cassettes with another resistant mechanism other than hydrolyze enzymes,e.g.increasing the function of the efflux pump in bacteria or/and reducing the outer membrane permeability of the bacteria against the antibiotics.Carbapenem-resistance gene cassettes were not detected and plasmid extraction was not successful.Conclusion The pseudomonas aeruginosa,which infected the patient repeatedly,has integronl at its chromosome.This IntegronI was significant for the resistance functions in the studied pseudomonas aeruginosa.
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