Comparative Evaluation of the In Vitro Antibacterial Activity of Preliminary Plant Preparations Against Phenotypically Multidrug‐Resistant Urinary Isolates of Escherichia Coli
Mohammad Ahmadian, Mohammad Javad Mehdipour Moghaddam, Davood BakhshiBackground
Urinary tract infections (UTIs) caused by multidrug‐resistant (MDR) Escherichia coli pose an increasing therapeutic challenge due to rising antibiotic resistance and limited treatment options. This study evaluated the antibacterial activity and phytochemical composition of plant preparations from Froriepia subpinnata and Eryngium caucasicum against MDR urinary E. coli isolates.
Methods
A total of 91 MDR E. coli isolates recovered from urine samples were examined. The antibacterial activities of the essential oil of Froriepia subpinnata (EoFs), the ethanolic extract of Froriepia subpinnata (EtFs), the ethanolic extract of Eryngium caucasicum (EtEc), the aqueous extract of Froriepia subpinnata (AqFs), and the aqueous extract of Eryngium caucasicum (AqEc) were assessed using agar well diffusion and broth microdilution assays to determine inhibition zones, minimum inhibitory concentrations (MIC), and minimum bactericidal concentrations (MBC). RP‐HPLC and GC–MS analyses were performed to conduct preliminary phytochemical profiling of the plant preparations and to generate a tentative chromatographic fingerprint of the essential oil, respectively.
Results
The isolates exhibited extensive resistance to the tested antibiotics. Among the plant‐derived preparations, EoFs showed the broadest descriptive antibacterial profile. Across the tested concentration range, EoFs inhibited 49 of 91 isolates (54%). At the highest tested concentration, inhibition and killing were observed in 25 (27%) and 15 (16%) isolates, respectively. The overall descriptive activity pattern was EoFs > EtFs > EtEc > AqFs > AqEc. MIC and MBC distributions differed significantly among the five preparations (Friedman′s test, p = 3.28 × 10 −7 and p = 1.37 × 10 −7 , respectively), although Kendall′s W values indicated small overall effect magnitudes ( W = 0.098 and W = 0.103, respectively). Holm‐adjusted pairwise comparisons showed lower MIC and MBC values for EoFs than for several other preparations. RP‐HPLC showed retention‐time correspondence with catechin and quercetin in some preparations, whereas no comparable peak for chlorogenic acid was observed under the conditions used. GC–MS provided a qualitative chromatographic fingerprint of EoFs, with NIST spectral‐library comparisons used for descriptive characterization.
Conclusion
F. subpinnata essential oil showed the strongest and most consistent antibacterial activity against MDR urinary E. coli . Although these findings highlight the potential of EoFs for further research, they do not establish clinical efficacy, a defined mechanism of action, or therapeutic equivalence to conventional antibiotics.