Introduction: Escherichia coli (E. coli), is the most common bacteria that cause urinary tract infections in women. Nowaday, many strains of E.coli have been resistant to beta-lactam antibiotics and bacterial Beta-lactamases, have an important role. The aim of this study was to investigate the role of thyme alcoholic extract on Extended-spectrum betalactamase (ESBL) producing strains of E.coli

Methods: After preparing the alcoholic extract of Zataria multiflora, concentrations 25, 50, 100, 200 and 400 μg /ml of this extract on ESBL-producing isolates of E.Coli was investigated, by agar disk diffusion method.

Results: The results showed that the inhibitory effect of  Zataria multiflora alcoholic extract on the growth of ESBL-producing strains of E. coli in concentrations 100 and 400 μg /ml, was significantly increased .(P<0.05)

Conclusion: Based on this study results, the alcoholic extract of Zataria multiflora has considerable inhibitory effects on ESBL-producing E. coli strains, in vitro.