Anti-methicillin Resistant Staphylococcus aureus Compound Isolation from Halophilic Bacillus amyloliquefaciens MHB1 and Determination of Its Mode of Action Using Electron Microscope and Flow Cytometry Analysis

Abstract

The aim of this study was to purify, characterize and evaluate the antibacterial activity of bioactive compound against methicillin-resistant Staphylococcus aureus (MRSA). The anti-MRSA compound was produced by a halophilic bacterial strain designated as MHB1. The MHB1 strain exhibited 99 % similarity to Bacillus amyloliquefaciens based on 16S rRNA gene analysis. The culture conditions of Bacillus amyloliquefaciens MHB1 were optimized using nutritional and environmental parameters for enhanced anti-MRSA compound production. The pure bioactive compound was isolated using silica gel column chromatography and Semi-preparative High-performance liquid chromatography (Semi-preparative HPLC). The Thin layer chromatography, Fourier transform infrared spectroscopy and proton NMR ( 1 H NMR) analysis indicated the phenolic nature of the compound. The molecular mass of the purified compound was 507 Da as revealed by Liquid chromatography-mass spectrometry (LC-MS) analysis. The compound inhibited the growth of MRSA with minimum inhibitory concentration (MIC) of 62.5 lg mL -1 . MRSA bacteria exposed to 49 MIC of the compound and the cell viability was determined using flow cytometric analysis. Scanning electron microscope and Transmission electron microscope analysis was used to determine the ultrastructural changes in bacteria. This is the first report on isolation of anti-MRSA compound from halophilic B. amyloliquefaciens MHB1 and could act as a promising biocontrol agent.

Antibacterial efficacy of silver nanoparticles and ethyl acetate’s metabolites of the potent halophilic (marine) bacterium, Bacillus cereus A30 on multidrug resistant bacteria

“…Whereas, ethyl acetate extract exhibited significant activity on MRSA, P. aeruginosa and E. coli which could be due to the presence of hentriacontane, that possesses antimicrobial properties as reported earlier by several researchers [56][57][58]. The antibacterial activity on antibiotic resistant MRSA was tested earlier by Jeyanthi and Velusamy [65], from the halophilic bacterium, Bacillus amyloliquefaciens MHB1, which is also in agreement with the presently evaluated inhibitory effect. Overall, the evaluated antibacterial activities of AgNPs synthesized from the halophilic bacterium, Bacillus cereus A30 was found to be more effective than ethyl acetate extracts on multi-drug resistant bacteria.…”

Effect of naturally isolated hydroquinone in disturbing the cell membrane integrity of Pseudomonas aeruginosa MTCC 741 and Staphylococcus aureus MTCC 740

“…Here the fluorescent probe PI, bound to the nucleic acid of dead and damaged cells with compromised bacterial membranes after 4 h of exposure to antibiotics. Similarly, in our previous study ( Jeyanthi and Velusamy 2016 ), the cell viability of MRSA treated with 4X MIC of the phenolic compound for different time intervals was investigated. The nucleic acid probe, PI bound to DNA by intercalating between the bases and emitted red fluorescence.…”

Antibacterial Activity of Extracts of Coprinopsis Cinerea, A Coprophilous Fungus Against Multidrug Resistant Nosocomial Pathogens

“…Time-kill kinetics studies were done according to Jeyanthi and Velusamy [12]. The 0.5,1 and 2×MIC of ethyl acetate extract was added separately to the bacterial culture density of 10 8 CFU/mL and incubated at 37°C.…”