Abstract

Infection with Helicobacter pylori is strongly associated with a number of gastroduodenal pathologies. Antimicrobial resistance to commonly-used drugs has generated a considerable interest in the search for novel therapeutic compounds from medicinal plants. As an ongoing effort of this search, the susceptibility of 32 clinical strains of H. pylori and a reference strain-NCTC 11,638-was evaluated against five solvent extracts of Combretum molle, a plant widely used for the treatment of gastric ulcers and other stomach-related morbidities in South Africa. The extracts were screened for activity by the agar-well diffusion method, and the most active one of them was tested against the same strains by micro-broth dilution and time kill assays. Metronidazole and amoxicillin were included in these experiments as positive control antibiotics. The solvent extracts all demonstrated anti-H. pylori activity with zone diameters of inhibition between 0 and 38 mm. The most potent anti-H. pylori activity was demonstrated by the acetone extract, to which 87.5% of the clinical strains were susceptible. The minimum inhibitory concentration (MIC90) values for this extract ranged from 1.25 to 5.0 mg/mL while those for amoxicillin and metronidazole ranged from 0.001 to 0.94 mg/mL and from 0.004 to 5.0 mg/mL respectively. The acetone extract was highly bactericidal at a concentration of 2.5 and 5.0 mg/mL, with complete elimination of the test organisms in 24 hours. Its inhibitory activity was better than that of metronidazole (p<0.05) as opposed to amoxicillin (p<0.05). The results demonstrate that C. molle may contain therapeutically-useful compounds against H. pylori, which are mostly concentrated in the acetone extract.

Highlights

  • Helicobacter pylori is a gram-negative microaerophilic spiral-shaped bacillus that affects the gastric mucosa and can be found attached to epithelial cells of the human stomach [1]

  • Antimicrobial susceptibility testing and determination of minimum inhibitory concentration All the crude extracts tested in this study demonstrated antimicrobial activity with zone diameters of inhibition ranging from 0 to 38 mm (Table 1)

  • The highest zone diameter of 38 mm was recorded for the acetone extract, to which 87.5% of the clinical strains were susceptible (Fig. 1)

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Summary

Introduction

Helicobacter pylori is a gram-negative microaerophilic spiral-shaped bacillus that affects the gastric mucosa and can be found attached to epithelial cells of the human stomach [1]. Important is the increasing prevalence of virulent strains, those expressing the cytotoxinassociated gene A antigen (CagA) associated with severe pathological conditions [11] that may be difficult to manage and post-therapeutic antibiotic resistance which has been known to decrease the cure rate by more than 50% [12]. These factors have generated a considerable interest in the search for alternative treatment regimens against this notorious pathogen. Alternative therapeutic agents with highly-selective antibacterial activity against the organism, without the risk of resistance or other untoward effects, are necessary [5]

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