Antimicrobial resistance and associated genes identified in extended-spectrum β-lactamases-producing Escherichia coli and Klebsiella pneumoniae

Objective To investigate the resistance and prevalence of extended-spectrumβ-lactamases (ESBLs) genotypes in Escherichia coli and Klebsiella pneumoniae which were isolated from lower respiratory tract between Jan 2002 and Dec 2003 in Shenzhen People's Hospital. Methods Sixty-one strains were confirmed as ESBLs-positive with inhibitor-potentiated test. The MICs were determined by agar dilution. ESBL genotypes were analyzed by PCR and nucleotide sequencing analysis. Results The susceptibility rate of ESBLs- producing strains were 100% to imipenem, MIC90 0. 5 mg/L. A total of 10 genotypes ofβ-lactamases were identified in the 61 ESBLs- producing strains. CTX-M type was identified in 83. 6% of the strains, including CTX-M-14 in 38 strains. SHV type was identified in 44. 3% of the strains, including SHV-12 in 20 strains. SHV genotype was identified only in K. pneumoniae. TEM type was identified in 37. 7% of the isolates. All of them were TEM-1. Conclusions ESBLs-producing E. coli and K. pneumoniae strains isolated from lower respiratory tract are highly resistant. Most strains are resistant to multiple drugs. CTX-M-type is the predominant ESBL genotypes in E. coli and K. pneumoniae, followed by SHV-type. Moreover, the distribution of ESBL genotypes is different in E. coli and K. pneumoniae, which may contribute to the different resistance patterns.