Tehran University Medical Journal

Background: Numerous use of Beta Lactame in treatment of bacterial infections resulted in increments of drug resistance of such bacteria. One of difficulties in treatment of hospital infections is Extended Spectrum Beta Lactamase (ESBL) among isolated clinical strains of E.coli. Since some of ESBL strains shows double reaction in drug sensitivity test at in vitro and in vivo condition, therefore it makes difficulties in selection of right treatment. In the last years, CTX-M enzymes have become the most prevalent ESBLs in worldwide. The prevalence of ESBL types largely remains unknown in many parts of the Iran. This study was made to find the prevalence of ESBL-producing E.coli and molecular detection of CTX-M-1 in Tabriz.

Methods: In the present study, 400 urine samples collected between November 2009 and April 2010, from Tabriz Hospitals were studied. Out of the 400 samples, 188 E.coli isolates were detected by standard biochemical tests. Susceptibility to antimicrobial agents was tested to 10 antibiotics by the disk agar diffusion (DAD) method. ESBL production was screened by phenotypic test that included both separate and combined disk agar diffusion techniques. The screened isolates were investigated by PCR assay to detect CTX-M-1 gene.

Results: From the total 188 E.coli isolates, 82 (43.6%) were shown to produce ESBLs by phenotypic test. During the PCR method on the 82 isolates, 69 (84.1%) were confirmed as CTX-M-1 producing group.

Conclusion: The present study showed that CTX-M-producing isolates were increasing among E.coli strains and indicated the need for adequate susceptibility tests in laboratories for choosing the appropriate antibiotics for treatment.