Background & objectives: Extended spectrum beta lactamases (ESBLs) have been observed in virtually all the species of family Enterobacteriaceae. The enzymes are predominantly plasmid mediated and are derived from broad-spectrum beta lactamase TEM-1, TEM-2 or SHV-1 by a limited number of mutations. This study was undertaken to characterize ESBL producers among Escherichia coli and Klebsiella pneumoniae by PCR-RFLP, which were initially screened by phenotypic method.
Methods: A total of 100 isolates of each species (E. coli and K. pneumoniae) were screened for ESBL production. PCR analysis for β-lactamase genes of the family TEM and SHV was also carried out. PCR products of TEM and SHV genes were subjected to digest with three different restriction enzymes. The digested products were run on 1.5 per cent agarose gel, stained and examined for DNA bands.
Results: PCR carried out on plasmid DNA alone detected 30 per cent ESBL positive isolates using TEM primer and 38 per cent using SHV primer, whereas PCR for both plasmid and chromosomal DNA showed 56 per cent positivity for TEM and 60 per cent positivity for SHV.
Interpretation & conclusion: RFLP yielded homogeneous band pattern, suggesting that there may be a point source or a common evolutionary origin for all the ESBL isolates.