Effects of the Aqueous Extract of Aloe vera on the Morphological and Physiological Properties of E. coli

Background Resistance to antibiotics is a growing worldwide problem. The inappropriate use of antibiotics has rendered some strains of bacteria resistant to antimicrobial drugs, making the treatment of infections much more difficult. However, many herbs and their derivatives are effective against drug resistant microbes. Objectives The aim of this research was to evaluate the effects of an Aloe vera extract on the morphological and physiological properties of Escherichia coli. Patients and Methods A clinical isolate of E. coli was obtained from a patient harboring a urinary tract infection (UTI), and was identified using biochemical and microbiological methods. Aqueous extracts of Aloe vera were prepared, and the minimum inhibitory concentration (MIC) of the extract was determined for E. coli via the microdilution method. The bacterium, at a concentration of 1.5 × 10⁸ cells/mL, was exposed to the MIC of the extract. Then, the morphology of the cells was studied using optical microscopy, and the physiological properties were studied using biochemical testing and differential culture media. Results The MIC of the Aloe vera extract was 2.23 mg/mL, and was able to prevent the growth of E. coli. The morphological examination of the bacteria exposed to the extract at the MIC revealed that the cells were shrunken, the concentration was reduced, the number of coccobacilli was increased, and the staining property of this bacteria changed (P < 0.0001). In addition, the extract caused a 76% reduction in the bacterial cell number, in comparison to the control (P < 0.0001), and a change in the physiological properties and growth of the bacteria. Conclusions This study showed that Aloe vera has antibacterial effects against E. coli, and can result in structural and physiological changes in this bacterium.