Antibacterial Potential of Endophytic Fungi Isolated from Psidium guajava (Guava) Leaf against Escherichia coli and Klebsiella pneumoniae

Abstract

Antimicrobial resistance has been recognized as a major issue of public health concern and it remains a global threat to the healthcare system. Endophytic fungi associated with medicinal plants are reported as a promising reservoir of novel antibiotics. The study aim was to determine the antibacterial potential of endophytic fungi associated with Psidium guajava leaf against Escherichia coli and Klebsiella pneumoniae. Leaves of P. guajava were surface sterilized and inoculated on plates of Potato Dextrose Agar and incubated at room temperature. Endophytic fungal isolates that emerged were identified using their macroscopic (cultural) and microscopic characteristics. The endophytes were screened for antibacterial activity on E. coli and K. pneumoniae isolates. Antibacterial activity of endophytic fungi ethyl acetate extracts with antibacterial activity was also evaluated against isolates of E. coli and K. pneumoniae by the agar well diffusion technique. Minimum Inhibitory Concentrations and Minimum Bactericidal Concentrations of the ethyl acetate extracts were also determined. Eight endophytic fungi were isolated from P. guajava leaves and four had antibacterial activity, namely: Gonatobotrys sp. P21, Xylaria sp. P11, Fusarium sp. P22, and Trichoderma sp. P25. The extracts exhibited antibacterial activity with zones of inhibition ranging from 11.5 ± 0.5 mm to 18.5 ± 1.5 mm for E. coli and 12.5 ± 0.5 mm to 21.0 ± 1.0 mm for K. pneumoniae. The MIC was found to be 500 mg/mL and 250 mg/mL for E. coli and K. pneumoniae respectively. Endophytic fungi isolated from P. guajava leaf are a potential source of novel antibacterial drugs since they possess antibacterial activity against isolates of E. coli and K. pneumoniae.