Detection of CTX-M-1 beta lactamase gene in Escherichia coli isolated from clinical samples by Polymerase Chain Reaction (PCR)

Resistance to beta-lactam antibiotics in clinical isolates frequently results from the production of β-lactamase enzymes. In recent years, the production of extended spectrum β-lactamases (ESBLs) and AmpC β-lactamase have greatly increased, especially in clinically isolated Escherichia coli. On the other hand, beta lactamase genes have several subfamilies and designing universal primers could be valuable in their detection. The beta-lactamase-producing E. coli which is resistant to beta-lactam antibiotics may pose a great risk to the patients. The CTX-M-1 gene is responsible for beta lactamase resistance. The purpose of this study was to find the percentage of CTX-M-1 carrying E. coli strains. A total of 500 urine samples were collected from different hospitals in Tehran, Iran during September to February 2009. The samples were cultured on EMB agar and incubated at 37 C for 24 hours. Some biochemical tests were carried out on the isolated samples. The presence of CTX-M-1 gene was determined by PCR on the isolates already identified phenotypically by disk diffusion agar and combined disks. In general, 200 out of the initial 500 samples were identified as E. coli, among which 128 (79.5%) were ESBLs producing strains. PCR used for the detection of CTX-M-1 gene, showed that 99 (77.34%) out of 128 isolates contained such gene. The results of this study showed a high percentage of β-lactamase resistant E. coli strains. This is a serious matter and would pose a public hazard and every step should be taken to avoid such hazard.