Study On Epidemiological Characterization Of Extended-spectrum Beta-lactamase-producing Klebsiella Pneumoniae Isolates

Klebsiella pneumoniae has emerged as an important nosocomial bacterial pathogen and it is very often resistant to most of the antimicirobial agents. Production of extended-spectrum beta- lactamases is a primary mechanism of resistance in the strains of Gram-negative bacterial especially in klebsiella pneumoniae. We study the susceptibility to several antimicrobial agents, genetyping and integron of 82 isolates of extended-spectrum beta-lactamase-producing klebsiella pneumoniae to investigate the resistance patterns, mechanism of resistance and its dissemination. It will contribute to a better control of the strain's prevalence and to a better selection of appreciate antibiotics.The method were as follows: 82 nonrepetitive(one per patient) clinical isolates of ESBLs- producing klebsiella pneumoniae were collected from February 2001 to June 2003 in the first affiliated hospital ,shantou university, medical college .The susceptibility of 10 antimicrobial agents (minimal inhibitory concentration, MIC) was measured by E-test. Genetyping of klebsiella pneumoniae was performed by pulsed-field gel electrophoresis(PFGE). PCR amplification were carried out with primers for int I 1 qacE 1 5' CS and 3' CS. The results of the experiment were as follows: 1. Susceptibility testing: Most of the isolates were multiplyresistant to the antimicrobials tested. The lowest antibiotic-resistant rate (4. 2%)was found in imipenem. The rate of resistant to cephalosporins used usually in shantou was higher than those used unusually in this area. Most of the isolates were highly resistant to aminoglycosides and tetracyclines. And most of them are also resistant to quinolones and piperacillin/tazobactam.2. Genetyping by PFGE: The restriction patterns obtained were consistent with the same strain in twice. 26 clones were found among 37 isolates of ESBLs-producing klebsiella pneuwoniae.3. Analysis of integron: PCR amplification with primer for int I 1 showed that fragment as excepted were obtained in 77isolates. PCR amplification with primer for qacEA 1 showed that fragment as excepted were obtained in 74 isolates. By PCR amplification with primer for 5' CS and 3' CS, fragment varied in sizes and numbers were obtained in 57 isolates. Conclusion:1. Imipenem was the most reliable antibiotics in treating infection caused by ESBLs-producing klebsiella pneumoniae. Therapeutic efficacy of Cephalosporins, aminoglycosides, quinolones and tetracycline were suspected. And piperacillin/tazobactam was also not reliable.2. Several clones transmission happened either in the same ward or in different wards during the period. And large-scale outbreak caused by the same clone didn' t happen. This indicated the disinfection and insulation measure in this hospital was good but still need improvement. And PFGE was a reliable technique in genetyping of bacteria.3. The prevalence of integron in ESBLs-producing klebsiella pneumoniae was high and the size and number of PCR product of each strain were different. This indicated that integron may play an important part in the spread of resistance.