Abstract
Introduction: The inevitable rise of
antibiotic-resistant bacteria is a global
health problem. These pathogens
erode the utility of available antibiotics.
Staphylococcus aureus is one of the major
causes of community-acquired infections.
The aim of work was to evaluate the
marine actinomycetes for production of
the antibacterial agent against pathogens.
Methods: Halophilic actinomycetes were
isolated, characterized and screened
for production of antibacterial agent against pathogenic bacteria. The antibacterial compounds
were extracted by solvent extraction and separated by TLC based bioautography. Antibacterial
compound was further purified by flash chromatography followed by high-performance liquid
chromatography (HPLC) techniques. The active fraction was characterized by spectroscopy
techniques. The minimum inhibitory concentration of antibiotic was determined against
pathogens.
Results: A new halophilic actinomycetes strain rsk4 was isolated from marine water. It was
designated as Kocuria sp. based on the physiological, biochemical and 16S rDNA sequencebased
characters. It was able to produce broad-spectrum antibacterial compound and exhibited
significant inhibitory activities against antibiotic-resistant S. aureus. The antibacterial compound
was secreted optimally at 5% NaCl and neutral pH in the starch casein medium during stationary
phase. The crude ethyl acetate extract was separated by chloroform-methanol, 24:1, v/v having Rf
value 0.45. Bioassay of HPLC fractions confirms the presence of antibiotics picks at retention time:
3.24 minutes. The UV-Visible and mass spectra of the compound revealed that the active compound
was different from other known antibiotics. The lowest minimum inhibitory concentration was
recorded against S. aureus (30 µg/mL).
Conclusion: The result suggests that a broad-spectrum antibacterial compound obtained from
halophilic actinomycetes is effective against pathogenic bacteria. This compound may be a good
alternative treatment against antibiotic-resistant pathogen S. aureus.