Évaluation de l’activité antibactérienne des extraits de champignons endophytes isolé de Macaranga hurifolia Beille et Voacanga thouarsii Roem. & Schult, sur quelques bactéries responsables des infections respiratoires.

Abstract

Respiratory infections are among the leading causes of infant mortality, representing a significant public health concern worldwide. The emergence of antibiotic-resistant strains in the context of unsuccessful treatment has prompted the development of novel therapeutic strategies. This study aims to assess the antibacterial activity of extracts from endophytic fungi of M. hurifolia and V. thouarsii against some respiratory tract pathogens. To this end, the leaves, bark, and wood of M. hurifolia and V. thouarsii were collected in Nkolbisson, Yaoundé, Cameroon, and identified at the National Herbarium. Subsequently, the plant material underwent a series of surface decontaminations, followed by inoculation into a PDA medium to obtain pure cultures. The cultures were identified on the PDA, SDA, and CDA media based on their morphological characteristics. The extraction of secondary metabolites was conducted using acetic ethyl acetate following the cultivation of the mushrooms in a rye-based medium. Subsequently, the inhibition tests (CMI and CMB) were conducted on the mycobacterial strains (BCG and H37RV ATCC 27294) and the Gram positive bacterial strains (S. aureus NCTC 12973, H. influenzae ATCC 49247, K. pneumoniae ATCC 17102, P. aeruginosa ATCC 76110, and E. coli ATCC 25922) using the microdilution method in liquid medium. The different classes of secondary metabolites present in the active extracts were identified through colorimetric tests. The results demonstrate that of the twenty-eight (28) characterized fungi, twenty-four (24) were identified as belonging to the following genera: Geotrichum (05), Neoscytalidium (05), Acremonium (04), Fusarium (04), Lasiodiplodia (04), Absidia (01), and Penicillium (01), with four (04) isolates remaining unidentified. Eight (08) fungal endophyte extracts were produced from these isolates. Extract “E11” demonstrated the greatest activity against all bacterial strains tested, with CMIs values ranging from 0.39 mg/mL against BCG and Pseudomonas aeruginosa strains to 1.56 mg/mL against the remaining bacterial strains. The chemical screening revealed the presence of flavonoids, phenols, polyphenols, saponins, and anthraquinones in all extracts.