Antimicrobial activity of three plant species against multi-drug resistant E. coli causing urinary tract infection

Abstract

The antimicrobial effects of aqueous and ethanolic extracts from three plants species including Matricaria chamomilla (AqMc, EtMc), Silybum marianum (AqSm, EtSm) and Melissa officinalis (AqMo, EtMo) and also the essential oil of M. chamomilla (EoMc) were investigated on 91 multidrug-resistant (MDR) E. coli isolates from patients with urinary tract infection (UTI). The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and also the inhibition zone diameter of the essential oil and extracts were determined by microdilution and agar well diffusion methods. Reversed-phase high- performance liquid chromatography (RP-HPLC) and gas chromatography-mass spectrometry (GC-MS) were applied for phytochemical analyses of extracts and essential oil ingredients especially flavonoids. The highest inhibitory activity was exhibited by EoMc (MIC = 0.11 μg/mL) and the lowest activity was for AqMc and AqSm (MIC = 1113 μg/mL). The highest bactericidal activity was attributed to EoMc and EtSm (MBC = 1.11 μg/mL) and the lowest activity was shown by AqMc (MBC = 1113 μg/mL). The EoMc can substitute 18 studied antibiotics except for meropenem and piperacillin (P < 0.01). In M. chamomilla and S. marianum, the ethanolic extracts exhibited more activity than the aqueous extracts, but in M. officinalis, the aqueous extract showed more antimicrobial effect than the ethanolic extract (P < 0.01). Antimicrobial compounds that were identified in the essential oil and extracts included flavonoids such as catechin, quercetin, and silymarin. The extracts or essential oil of these studied plants are good candidates to use in the treatment of UTI due to MDR E. coli; although they need more investigation.