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<p>To address the contemporary escalating challenge of antimicrobial resistance (AMR) pathogens, this study aimed to explore marine-associated fungi as a source of antibacterial metabolites against multidrug-resistant (MDR) bacteria. Ten different fungi were isolated from five diverse marine samples collected from the Narara Reef region of Gujarat, India, and subsequently evaluated for their antagonistic activity against a broad range of bacterial pathogens. Among the ten isolates, the sponge-associated fungal strain AF5 demonstrated potent antagonistic activity against seven Gram-positive bacterial pathogens, including Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) and Vancomycin-resistant <i>Enterococcus faecalis</i> (VRE). However, no significant antagonistic activity was observed against the Gram-negative bacterial pathogens tested. Further morphological, molecular, and phylogeny analyses based on Internal Transcribed Spacer&#xa0;sequencing (ITS), Large Subunit<b> (</b>LSU), and beta-tubulin<b> (</b><i>tub2</i>) loci identified the fungal isolate AF5 as <i>Amesia atrobrunnea</i>. Optimization studies revealed that among the four media tested, potato dextrose broth and Czapek yeast extract broth supported the highest antibiotic production, yielding inhibition zones of 24.62 ± 1.2&#xa0;mm and 24.84 ± 0.5&#xa0;mm, respectively, after 16&#xa0;days of incubation. Among the solvents tested, chloroform exhibited the highest extraction efficiency, producing the largest inhibition zone (24.12 ± 0.3&#xa0;mm) and an extraction yield of 2.814 ± 0.641&#xa0;mg/g. The crude chloroform extract displayed notable antibacterial activity, producing inhibition zones of 15.00 ± 0.00&#xa0;mm against multidrug-resistant <i>Staphylococcus aureus</i> (MDRSA) and 9.00 ± 1.00&#xa0;mm against Multidrug-resistant <i>Enterococcus faecalis</i> (MDREF). It also displayed potent antibacterial activity at the lowest concentration against MRSA with MIC 3.90&#xa0;µg/mL, MBC 7.81&#xa0;µg/mL, and moderate activity against VRE with MIC and MBC 31.25&#xa0;µg/mL. Further, GC–MS analysis of the bioactive TLC fractions C3 and C4 revealed 2,4-di-tert-butylphenol, tris(2,4-di-tert-butylphenyl) phosphate, and 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione as the predominant compounds potentially associated with the observed antibacterial activity. To our knowledge, this is the first report of a marine-derived <i>Amesia atrobrunnea</i> strain (AF5) producing bioactive metabolites with potent antibacterial activity against Gram-positive multidrug-resistant (MDR) pathogens.</p>

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Antibacterial potential of marine sponge-associated fungus Amesia atrobrunnea strain AF5 against multidrug-resistant Gram-positive bacteria

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Avani Bhimani,
  • Yashwantsinh Jadeja,
  • Ashok Kumar Bishoyi

摘要

To address the contemporary escalating challenge of antimicrobial resistance (AMR) pathogens, this study aimed to explore marine-associated fungi as a source of antibacterial metabolites against multidrug-resistant (MDR) bacteria. Ten different fungi were isolated from five diverse marine samples collected from the Narara Reef region of Gujarat, India, and subsequently evaluated for their antagonistic activity against a broad range of bacterial pathogens. Among the ten isolates, the sponge-associated fungal strain AF5 demonstrated potent antagonistic activity against seven Gram-positive bacterial pathogens, including Methicillin-resistant Staphylococcus aureus (MRSA) and Vancomycin-resistant Enterococcus faecalis (VRE). However, no significant antagonistic activity was observed against the Gram-negative bacterial pathogens tested. Further morphological, molecular, and phylogeny analyses based on Internal Transcribed Spacer sequencing (ITS), Large Subunit (LSU), and beta-tubulin (tub2) loci identified the fungal isolate AF5 as Amesia atrobrunnea. Optimization studies revealed that among the four media tested, potato dextrose broth and Czapek yeast extract broth supported the highest antibiotic production, yielding inhibition zones of 24.62 ± 1.2 mm and 24.84 ± 0.5 mm, respectively, after 16 days of incubation. Among the solvents tested, chloroform exhibited the highest extraction efficiency, producing the largest inhibition zone (24.12 ± 0.3 mm) and an extraction yield of 2.814 ± 0.641 mg/g. The crude chloroform extract displayed notable antibacterial activity, producing inhibition zones of 15.00 ± 0.00 mm against multidrug-resistant Staphylococcus aureus (MDRSA) and 9.00 ± 1.00 mm against Multidrug-resistant Enterococcus faecalis (MDREF). It also displayed potent antibacterial activity at the lowest concentration against MRSA with MIC 3.90 µg/mL, MBC 7.81 µg/mL, and moderate activity against VRE with MIC and MBC 31.25 µg/mL. Further, GC–MS analysis of the bioactive TLC fractions C3 and C4 revealed 2,4-di-tert-butylphenol, tris(2,4-di-tert-butylphenyl) phosphate, and 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione as the predominant compounds potentially associated with the observed antibacterial activity. To our knowledge, this is the first report of a marine-derived Amesia atrobrunnea strain (AF5) producing bioactive metabolites with potent antibacterial activity against Gram-positive multidrug-resistant (MDR) pathogens.