Background: Escherichia coli occurs naturally in the human gut; however, certain strains that can cause infections, are becoming resistant to antibiotics. Multidrug-resistant E. coli that produce extended-spectrum beta lactamases (ESBLs), such as the CTX-M enzymes, have emerged within the community setting as an important cause of urinary tract infections (UTIs) and bloodstream infections may be associated with these community-onsets. This is the first report testing the antibiotic resistance-modifying activity of nineteen Jordanian plants against multidrug-resistant E. coli.
Methods: The susceptibility of bacterial isolates to antibiotics was tested by determining their minimum inhibitory concentrations (MICs) using a broth microdilution method. Nineteen Jordanian plant extracts (Capparis spinosa L., Artemisia herba-alba Asso, Echinops polyceras Boiss., Gundelia tournefortii L, Varthemia iphionoides Boiss. & Blanche, Eruca sativa Mill., Euphorbia macroclada L., Hypericum trequetrifolium Turra, Achillea santolina L., Mentha longifolia Host, Origanum syriacum L., Phlomis brachydo(Boiss.) Zohary, Teucrium polium L., Anagyris foetida L., Trigonella foenum-graecum L., Thea sinensis L., Hibiscus sabdariffa L., Lepidium sativum L., Pimpinella anisum L.) were combined with antibiotics, from different classes, and the inhibitory effect of the combinations was estimated.
Results: Methanolic extracts of the plant materials enhanced the inhibitory effects of chloramphenicol, neomycin, doxycycline, cephalexin and nalidixic acid against both the standard strain and to a lesser extent the resistant strain of E. coli. Two edible plant extracts (Gundelia tournefortii L. and Pimpinella anisum L.) generally enhanced activity against resistant strain. Some of the plant extracts like Origanum syriacum L.(Labiateae), Trigonella foenum- graecum L.(Leguminosae), Euphorbia macroclada (Euphorbiaceae) and Hibiscus sabdariffa (Malvaceae) did not enhance the activity of amoxicillin against both standard and resistant E. coli. On the other hand combinations of amoxicillin with other plant extracts used showed variable effect between standard and resistant strains. Plant extracts like Anagyris foetida (Leguminosae) and Lepidium sativum (Umbelliferae) reduced the activity of amoxicillin against the standard strain but enhanced the activity against resistant strains. Three edible plants; Gundelia tournefortii L. (Compositae) Eruca sativa Mill. (Cruciferae), and Origanum syriacum L. (Labiateae), enhanced activity of clarithromycin against the resistant E. coli strain.
Conclusion: This study probably suggests possibility of concurrent use of these antibiotics and plant extracts in treating infections caused by E. coli or at least the concomitant administration may not impair the antimicrobial activity of these antibiotics.