Abstract
Fungi from the widely distributed genus Trichoderma are of great biotechnological interest, being currently used in a vast range of applications. Here, we report that high-molecular weight fraction (HWF) derived from Trichoderma asperelloides ethanolic extract exhibits antibiotic activity against staphylococcal biofilms. The antibacterial and anti-biofilm properties of T. asperelloides extracts were evaluated by well-established assays in Staphylococcus aureus ATCC strains (29213 and 6538) and in one clinical isolate from bovine mastitis. The HWF from T. asperelloides eradicated S. aureus by causing substantial matrix de-structuring and biomass reduction (p < 10−5) at concentrations as low as 2.3 μg mL-1. Additionally, we present ultra-structure analysis by the use of scanning electron microscopy as well as transmission microscopy, which showed that T. asperelloides killed cells through cell wall and membrane disturbance. Remarkably, the HWF from T. asperelloides killed S. aureus and eradicated its biofilms in a greater performance than gentamicin (p < 10−5), a known potent antibiotic against S. aureus. Our results indicate that extract from T. asperelloides may represent a promising candidate for the development of new antibiotics against gram-positive bacteria.
Highlights
The genus Trichoderma comprises filamentous fungi species that are decomposers and components of the microflora, present in all soil types as well as the rhizosphere and organic matter [1,2]
By analyzing the growth curve of different S. aureus strains cultured with different concentrations of ethanolic extracts from T. asperelloides, we demonstrated that total extract (TE) and high-molecular weight fraction (HWF) have strong effect on killing S. aureus (Fig 1)
After treating biofilm-forming strains with different concentrations of ethanolic extracts for 24 hours, we showed that TE and HWF (Fig 2A, 2B, 2C, 2D, 2E and 2F) efficiently controlled biofilm formation in comparison to controls (p < 10−5)
Summary
The genus Trichoderma comprises filamentous fungi species that are decomposers and components of the microflora, present in all soil types as well as the rhizosphere and organic matter [1,2]. Trichoderma exhibits efficient colonization ability as well as effect in plant health by controlling several phytopathogens [3]. One of the factors that contribute to the success full colonization of Trichoderma species is their ability of secreting enzymes and antibiotics [4]. Trichoderma asperelloides inhibit Staphylococcus biofilm formation metabolic versatility of Trichoderma fungi make them good candidates for drug discovery against infections caused by fungal, viral and bacterial pathogens, which cause diseases in plants and animals, including humans [5,6]. Staphylococcus aureus is one of the major opportunistic pathogens that colonize a considerable portion of the human population [8,9,10]. An important factor that affects its pathogenicity is its ability to firmly adhere to prosthetic materials and the formation of biofilms on several surfaces, which includes pacemakers, implants and catheters. Staphylococcus produces a variety of toxins, besides their ability to develop resistance against antimicrobial agents [12,13]
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