Background: There are numerous types of extended spectrum beta-lactamases (ESBLs), of which TEM and SHV are predominant among Klebsiella pneumoniae strains. Nosocomial infections with strains of K. pneumoniae are common in healthcare centers in Iran. However, no information is available on the prevalence of different phenotypes of ESBL strains in Tehran hospitals.
Material/Methods: To determine the resistance of K. pneumoniae to beta-lactam antibiotics in Tehran hospitals, 145 isolates were tested using the disk diffusion method. The MICs for ceftazidime were also determined using microbroth dilution assay. Isolates showing MIC ≥4 for ceftazidime were subjected to PCR to target the bla[sub]SHV[/sub] and bla[sub]TEM[/sub] genes and screened for ESBL production by the phenotypic confirmatory method.
Results: All strains were susceptible to imipenem. Resistance to ceftazidime and cefotaxime were 31% and 32%, respectively. Fifty-six isolates showed MIC ≥4 µg/ml for ceftazidime, of which 50 were positive for ESBL in the phenotypic confirmatory test. The prevalence of bla[sub]SHV[/sub] and bla[sub]TEM[/sub] among these isolates was 69.6% (n=39) and 32.1% (n=18), respectively. Resistance to ciprofloxacin was found among 32% of the ESBL strains.
Conclusions: SHV is the dominant enzyme among the ESBL-producing strains of Klebsiella pneumoniae in Iran. The high rate of co-resistance to ceftazidime and ciprofloxacin is a matter of concern and treatment requires further attention to the results of susceptibility.

Keywords: Base Sequence, beta-Lactamases - genetics, Polymerase Chain Reaction, Microbial Sensitivity Tests, Klebsiella pneumoniae - isolation & purification, Klebsiella Infections - microbiology, Iran, Genes, Bacterial, Drug Resistance, Bacterial, DNA, Bacterial - genetics, DNA Primers - genetics, Cross Infection - microbiology, Ceftazidime - pharmacology, Cefotaxime - pharmacology, Base Sequence, beta-Lactamases - genetics, Polymerase Chain Reaction, Microbial Sensitivity Tests, Klebsiella pneumoniae - isolation & purification, Klebsiella Infections - microbiology, Iran, Genes, Bacterial, Drug Resistance, Bacterial, DNA, Bacterial - genetics, DNA Primers - genetics, Cross Infection - microbiology, Ceftazidime - pharmacology, Cefotaxime - pharmacology