In vitro antibacterial activity of aqueous extracts of 𝘛𝘦𝘳𝘮𝘪𝘯𝘢𝘭𝘪𝘢 𝘤𝘩𝘦𝘣𝘶𝘭𝘢 and 𝘛𝘦𝘳𝘮𝘪𝘯𝘢𝘭𝘪𝘢 𝘣𝘦𝘭𝘭𝘪𝘳𝘪𝘤𝘢 fruits against some multidrug-resistant human pathogens

Abstract

Alternative approaches in the treatment of bacterial infections are urgently required because of the emergence of antibiotic resistant mutants due to the increased use and misuse of antibiotics. Plants appear to be a valuable source for new antimicrobials that can be employed in combating drug-resistance. The extracts of 𝘛𝘦𝘳𝘮𝘪𝘯𝘢𝘭𝘪𝘢 𝘤𝘩𝘦𝘣𝘶𝘭𝘢 𝘙𝘦𝘵𝘻. (Combretaceae) and 𝘛𝘦𝘳𝘮𝘪𝘯𝘢𝘭𝘪𝘢 𝘣𝘦𝘭𝘭𝘪𝘳𝘪𝘤𝘢 𝘙𝘰𝘹𝘣. fruits are known to have antibacterial properties. However, the data on their activity against multidrug resistant human pathogens is limited. The current study was undertaken to evaluate the antibacterial activity of aqueous extracts of 𝘛. 𝘤𝘩𝘦𝘣𝘶𝘭𝘢 and 𝘛. 𝘣𝘦𝘭𝘭𝘪𝘳𝘪𝘤𝘢 fruits against methicillin-resistant Staphylococcus aureus (MRSA), extended spectrum β-lactamase (ESBL) producing 𝘌𝘴𝘤𝘩𝘦𝘳𝘪𝘤𝘩𝘪𝘢 𝘤𝘰𝘭𝘪 and multidrug-resistant (MDR) 𝘈𝘤𝘪𝘯𝘦𝘵𝘰𝘣𝘢𝘤𝘵𝘦𝘳 𝘴𝘱𝘱, 𝘒𝘭𝘦𝘣𝘴𝘪𝘦𝘭𝘭𝘢 𝘱𝘯𝘦𝘶𝘮𝘰𝘯𝘪𝘢𝘦 and 𝘗𝘴𝘦𝘶𝘥𝘰𝘮𝘰𝘯𝘢𝘴 𝘢𝘦𝘳𝘶𝘨𝘪𝘯𝘰𝘴𝘢.

Aqueous extracts of dried and powdered 𝘛. 𝘤𝘩𝘦𝘣𝘶𝘭𝘢 and 𝘛. 𝘣𝘦𝘭𝘭𝘪𝘳𝘪𝘤𝘢 fruits were prepared by three methods - heating under reflux, bottle-shaking and ultrasound sonication at ambient temperature. Using the cut-well method, all the aqueous extracts were screened against 8 MRSA strains, 2 ESBL producing 𝘌. 𝘤𝘰𝘭𝘪 strains, 2 strains of MDR 𝘈𝘤𝘪𝘯𝘦𝘵𝘰𝘣𝘢𝘤𝘵𝘦𝘳 𝘴𝘱𝘱, 2 strains of MDRK. 𝘱𝘯𝘦𝘶𝘮𝘰𝘯𝘪𝘢𝘦 and 2 strains of MDR 𝘗. 𝘢𝘦𝘳𝘶𝘨𝘪𝘯𝘰𝘴𝘢 𝘚. 𝘢𝘶𝘳𝘦𝘶𝘴 ATCC 25923 and NCTC 6571, 𝘌. 𝘤𝘰𝘭𝘪 ATCC 25922 and ESBL producing 𝘒. 𝘱𝘯𝘦𝘶𝘮𝘰𝘯𝘪𝘢𝘦 ATCC 70060 served as control organisms. The minimum inhibitory concentration (MIC) was determined using the agar dilution method.

All six aqueous extracts displayed antibacterial activity against all the strains of MRSA, MDR 𝘈𝘤𝘪𝘯𝘦𝘵𝘰𝘣𝘢𝘤𝘵𝘦𝘳 𝘴𝘱𝘱 and MDR 𝘗. 𝘢𝘦𝘳𝘶𝘨𝘪𝘯𝘰𝘴𝘢 within the range of 0.25-4 mg/ml.Furthermore, all three aqueous extracts of 𝘛. 𝘤𝘩𝘦𝘣𝘶𝘭𝘢 displayed antibacterial activity against ESBL-producing 𝘌. 𝘤𝘰𝘭𝘪 at 5 mg/ml. The extracts obtained by the reflux method showed the highest antibacterial activity for both the fruits with MIC valuesof 0.25-0.5, 0.51and < 0.125-0.5 mg/ml for MRSA, MDR 𝘈𝘤𝘪𝘯𝘦𝘵𝘰𝘣𝘢𝘤𝘵𝘦𝘳 𝘴𝘱𝘱 and MDR 𝘗. 𝘢𝘦𝘳𝘶𝘨𝘪𝘯𝘰𝘴𝘢, respectively. However, aqueous extracts of both fruit samples obtained by thethree extraction methods did not exhibit activity against MDR 𝘒. 𝘱𝘯𝘦𝘶𝘮𝘰𝘯𝘪𝘢𝘦 at or below 5 mg/ml. The aqueous extracts of 𝘛. 𝘤𝘩𝘦𝘣𝘶𝘭𝘢 demonstrated comparatively high antibacterial activity than 𝘛. 𝘣𝘦𝘭𝘭𝘪𝘳𝘪𝘤𝘢.