Anti-bacterial effect of essential oil from Xanthium strumarium against shiga toxin-producing Escherichia coli.

Shiga toxin-producing Escherichia coli (STEC) serotype O157:H7 is one of the most important human pathogenic microorganisms, which can cause life-threatening infections. Xanthium strumarium L. is a plant with anti-bacterial activity against gram-negative and gram-positive bacteria. This study aims to demonstrate in vitro efficacy of the essential oil (EO) extracted from Xanthium strumarium L. against E. coli O157:H7. Using the agar test diffusion, the effect of Xanthium strumarium L. EO (5, 10, 15, 30, 60, and 120 mg/mL) was verified at each of the four different growth phases of E. coli O157:H7. Cell counts of viable cells and colony forming unit (CFU) were determined at regular time points using Breed's method and colony counting method, respectively. No viable cell was detectable after the 1 hour-exposure to X. strumarium EO at 30, 60, and 120 mg/mL concentrations. No bacterial colony was formed after 1 h until the end of the incubation period at 24 h. At lower concentrations, the number of bacteria cells decreased and colonies could be observed only after incubation. At the exponential phase, the EO at 15 mg/mL was only bacteriostatic, while from 30 mg/mL started to be bactericidal. X. strumarium EO antibacterial activity against Shiga toxin-producing E. coli O157:H7 is dependent on EO concentration and physiological state of the microorganisms tested. The best inhibitory activity was achieved during the late exponential and the stationary phases.

Antibacterial activities of essential oils from Iranian medicinal plants on extended-spectrum ß-lactamase-producing Escherichia coli.

The extended-spectrum beta-lactamase (ESBL) -producing Escherichia coli strains can lead to various infections particularly urinary tract infections. The main objective of this investigation was to evaluate the antibacterial activities of essential oils (EOs) from different Iranian medicinal plants against TEM gene positive ESBL-producing E. coli strains isolated from urine samples of patients with urinary tract infections. EOs were extracted using hydrodistillation method. E. coli strains were isolated by different specific Medias. ESBL-producing E. coli strains were isolated from urine samples of patients with urinary tract infections in Shiraz hospital, Iran. Then, ESBL- producing strains were identified using double disk synergy test, phenotypic disc confirmatory test and polymerase chain reaction (PCR) for TEM gene detection. The antibacterial activity of the EOs from different plants (Achillea wilhelmsii C. Koch, Echinophora platyloba DC., Lallemantia royleana, Nepeta persica Boiss., Pulicaria vulgaris Gaertn., Salvia nemorosa, and Satureja intermedia C.A.Mey) and antibiotics against ESBL-producing strains was studied using the microdilution method for the evaluation of the minimum inhibitory concentration (MIC). The 103 out of 295 E. coli strains with 97 (90.65%) TEM gene distributions were identified as ESBL-producing strains. All of the EOs derived from different plants displayed high inhibitory effects against ESBL-producing E. coli strains. The results of our investigations may propose a good treatment option against resistant infectious bacteria.