Antibiotic resistance and genotypes of β-lactamases of continuously isolated Escherichia coli and Klebsiella pneumoniae strains

OBJECTIVE To investigate the β-lactamase genes in continuously isolated Escherichia coli and Klebsiella pneumoniae strains so as to provide basis for clinical medication and conerol of nosocomial infection.METHODS The identification and drug susceptibility testing of clinical strains were performed by MicroScan auto-Scan4.The double-disk diffusion method was used to detect the ESBLs-producing strains.PCR was used for the detection of the 21 β-lactamase genes.RESULTS Totally 159 clinical strains were collected,among which 81 strains were confirmed to produce β-lactamases.There were 12 kinds of genes and 123 gene fragments such as TEM,SHV,OXA-1,and CTX-M-1.TEM was the most common type of the β-lactamase gene in the clinical strains of E.coli(33.3%),but SHV was the most common type in K.pneumoniae(27.9%).There were 16 genotypes and 51.9% of the strains produced more than two β-lactamase genes.Among 13 AmpC-producing strains,4 strains produced AmpC β-lactamases and ESBLs.CONCLUSION The carrying rate of β-lactamase gene is high in continuously isolated E.coli and K.pneumoniae strains in the locality and most strains are multidrug-resistant.It is very important to enhance the surveillance of the β-lactamase-producing strains and to strictly grasp the indication for antibiotic application so as to prevent the spread of the drug resistance strains.