Antimicrobial Activities of the Secondary Metabolite Extracted from a Nocardia Strain

Marjan Seratnahaei; Seyyed Saeed Eshraghi; Parviz Pakzad; Alireza Zahraei Ramazani; Mehdi Yaseri

doi:10.18502/jabs.v12i2.9886

Marjan Seratnahaei Department of Microbiology, Faculty of Basic Sciences, North Tehran Branch, Islamic Azad University, Tehran, Iran
Seyyed Saeed Eshraghi Department of Pathobiology, Faculty of Public Health, Tehran University of Medical Science, Tehran, Iran
Parviz Pakzad Department of Microbiology, Faculty of Basic Sciences, North Tehran Branch, Islamic Azad University, Tehran, Iran
Alireza Zahraei Ramazani Department of Medical Entomology and Vector Control, Faculty of Public Health, Tehran University of Medical Sciences, Tehran, Iran
Mehdi Yaseri Department of Epidemiology and Biostatistics, Tehran University of Medical Sciences, Tehran, Iran

DOI: https://doi.org/10.18502/jabs.v12i2.9886

Keywords: Nocardia soli; antimicrobial activity; HPLC; Bioactive metabolite

Abstract

Background & Objective: The emergence of antibiotic-resistant bacteria and limited treatment options for these infections is a challenging problem in the world. There is increasing interest in isolating bioactive molecules from actinobacteria and elucidating their antimicrobial mechanisms at the moment. The current study aimed to investigate the antimicrobial activities of a Nocardia strain (N4) that was previously isolated from the soil samples in Tehran, Iran.

Materials & Methods: The cultural, morphological, and physiological characteristics of the strain were determined and the identity of the strain was confirmed using 16SrRNA gene sequencing. The strain was screened for antimicrobial metabolite production. The in vitro anti-microbial activity of the extracted metabolite was assessed by agar well diffusion and minimum inhibitory concentrations methods. Finally, the structure of the extracted metabolite was confirmed by HPLC and mass spectrometry methods.

Results: The isolate shared 99% sequence similarity with Nocardia soli. The strain showed broad-spectrum antimicrobial activities against some pathogenic bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 700603, Salmonella Typhimurium ATCC 14028 and Shigella sonnei RI366) and fungi (Aspergillus niger ATCC 1015 and Aspergillus fumigatus ATCC 1022) in the agar well diffusion method. The ethyl acetate extract of the strain exhibited the highest antimicrobial activity against E. coli (MIC= 4.67±3.055 μg/mL) and K. pneumoniae (MIC=3.33±1.155 μg/mL). The metabolite showed high similarity with C2 1H28N7 O14.

Conclusions: The current study confirmed the presence of a bioactive metabolite in strain N4, suggesting that this may be a promising candidate for discovering bioactive components with broad antibacterial activities against a variety of pathogens.