Development of bacterial resistance to the antimicrobials recovered from an aqueous fruit extract of Xylopia aethiopica

Abstract

Recently, the use of antibiotics for the treatment of numerous infections and diseases increased significantly, and led to noticeable reduction in the rate of mortality and morbidity. The increased development of multidrug resistant bacterial strains that is attributable to the indiscriminate use of antibiotics has led to the search for new antimicrobials of plants origin. This study aimed to assess the potentials of the multidrug resistant bacterial strains to develop resistance to the aqueous fruit extract of Xylopia aethiopica. The tested bacterial strains were; Staphylococcus epidermidis, Staphylococcus saprophyticus, Bacillus cereus, Pseudomonas aeruginosa and Escherichia coli. In this study, on using the in vitro agar well diffusion assay; the bacterial strains exhibited different diameters of zones of inhibition; ranging from 1.75± 1.06 mm to 12.75± 1.06 mm, on treatment with various concentrations of the aqueous fruit extract. The recorded MIC value for E. coli was 250 mg/ ml, while the other bacterial strains recorded 125 mg/ ml. On the other hand, the obtained MBC value for Staphylococcus saprophyticus and Staphylococcus epidermidis was 2000 mg/ ml, whereas E. coli and P. aeruginosa recorded 1000 mg/ ml. However, the MBC of B. cereus was not detected. The bacterial strains were subjected to a sub-optimal concentration of the extract after exposure for 5, 10, 15 and 20 d. After exposure for 20 d, P. aeruginosa expressed sensitivity only at 2000 mg /ml of the extract with a diameter of inhibition of 4.25± 0.35 mm. E. coli exhibited sensitivity at 2000 and 1000 mg/ ml, recording diameters of inhibition of 4.5± 0.71 mm and 2.50± 0.71 mm, respectively. The other strains exhibited resistance on treatment with 250 mg/ ml of the extract, except for B. cereus, which recorded inhibition diameter of 3.50 ±0.71 mm. This study demonstrated that exposure of the MDR resistant bacterial strains to a sub-optimal concentration of the aqueous fruit extract of Xylopia aethiopica could initiate resistance development.