Exposure to Plant Extract Causes the Variation of Antibiotic Susceptibility of Two Bacterial Strains (Salmonella Serotype Typhi and Staphylococcus aureus)

Introduction: Several authors have associated the development of antibiotic resistance to the use of antibiotics. But this development of resistance could also be associated with plant extracts. This article explores the impact of exposure to different plant extracts of Salmonella serotype Typhi and Staphylococcus aureus on their sensitivity to antibiotics.

Methods: According to the informations obtained from traditional medicine healers, 13 plants powders from different parts were selected to compose mixtures that were used to produce the extract by decoction. The susceptibility test through inhibition diameter analyses and the minimal inhibition concentration were performed using the decoctions and the two strains. Different microorganisms were exposed to a fresh broth containing the extract at fixed or increased concentration in every 24 h for 14 days. Subsequently, after the 14 days, these strains were grown in the same broth renewed at 24 h without added extract for another 14 days. Antibiogram using three antibiotics was performed at 48 h. Variation of inhibition diameter was used to evaluate the impact of extract exposure to the sensitivity.

Results: The two strains subjected to a molecular pressure of the plant extracts acquired resistance to the antibiotics tested, regardless of the concentration of the plant extract used for the exposure. The sensitivity of Salmonella Typhi exposed to two of the decoctions decreased vis-a-vis the three antibiotics tested and this decrease persisted 14 days repeated sowing in new broth without plant extract despite the lack of antimicrobial. In addition, exposure of Staphylococcus aureus to the extracts of Chromoleana odorata and Erigeron floribundus showed a decrease in sensitivity of this strain to Erythromycin. But this sensitivity compared to other antibiotics has decreased after non antimicrobial exposure.

Conclusion: This study shows that continuous exposure of bacteria to some plant extracts reduces the sensitivity of these strains. As a result, the development of antibiotic resistance is not only related to the uncontrolled use of antibiotics.