Screening for antimicrobial activity in fungi isolated from Lebanese soil

Abstract

Microorganisms abound in the soil. They secrete secondary metabolites that kill pathogens affecting human and animal health. The emergence of pathogens resistance toward antimicrobial substances is exponentially increasing these years. Thus new antibiotics are required to counteract this crisis. The aim of this research is to screen any antimicrobial activity in fungi isolated from soil in the region of Batroun. Effects were examined against sensitive Escherichia coli, sensitive Staphylococcus aureus, Extended Spectrum Beta Lactamase producing Escherichia coli, Methicillin Resistant Staphylococcus aureus and Acinetobacter baumannii. Soil samples were collected at altitudes ranging from 124 m to 622 m. Twelve fungal colonies were able to inhibit the growth of at least one of these six bacterial strains. Fungal colonies were identified as Altenaria sp., Aspergillus versicolor, Onychocola canadensis, Penicillium sp. and Trichoderma sp. Antimicrobial substances present in fungal extracts were then tested to observe their Minimal Inhibitory and Bactericidal Concentrations. Onychocola canadensis, Aspergillus versicolor and Altenaria sp. were able to secrete antimicrobial substances having a bactericidal effect against gram positive bacteria. On the other hand Trichoderma sp isolate has a bactericidal effect against sensitive E. coli, and bacteriostatic effect sensitive S. aureus, MRSA, P. aeruginosa and A. baumannii. Finally seven Penicillium isolates had antimicrobial activity against these pathogens. One Penicillium colony isolated from Hamet soil showed bactericidal activity against A. baumannii.