Fungal-derived xenobiotic exhibits antibacterial and antibiofilm activity against Staphylococcus aureus

Antimicrobial effect of pimozide by targeting ROS-mediated killing in Staphylococcus aureus

In spite of the higher nosocomial and community-acquired infections caused by Staphylococcus aureus, emerging drug resistance is a leading cause of increased mortality and morbidity associated with the overuse of antimicrobials. It is an emergent need to find out new molecules to combat such infections. In the present study, we analyzed the antibacterial effect of pimozide (PMZ) against gram-positive and gram-negative bacterial strains, including methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) S. aureus. The growth of MSSA and MRSA was completely inhibited at concentrations of 12.5 and 100 μg/mL, respectively, which is referred to as 1× minimum inhibitory concentration (MIC). The cell viability was completely eliminated within 90 min of PMZ treatment (2× MIC) through reactive oxygen species (ROS)-mediated killing without affecting cell membrane permeability. It suppressed α-hemolysin production and biofilm formation of different S. aureus strains by almost 50% at 1× MIC concentration, and was found to detach matured biofilm. PMZ treatment effectively eliminates S. aureus infection in Caenorhabditis elegans and improves its survival by 90% and is found safe to use with no hemolytic effect on human and chicken blood tissues. Taken together, it is concluded that PMZ may turn out to be an effective antibacterial for treating bacterial infections including MSSA and MRSA.

Enhanced Antibacterial and Photoluminescence Activities of ZnSe Nanostructures

Microorganisms create various health issues; semiconductor nanostructures have raised interest because of antimicrobial properties for suppressing microbial growth. Herein, we report the synthesis of ZnSe nanostructures (NSs) using a green coprecipitation method, and the as-synthesized samples were annealed at 100, 150, and 200 °C temperatures. The synthesized samples were analyzed for structural, morphological, optical, and antibacterial properties. The growth of nanorods was confirmed by TEM micrographs and that of nanoparticles by FESEM and TEM micrographs. The cubic zinc blender phase of samples was confirmed by XRD. The high-intensity electron-phonon (e-ph) interactions and LO modes were confirmed by the Raman spectra. The UV-visible absorption spectra predicted the blue shift in optical band gaps of ZnSe NSs from their bulk counterparts. The PL spectra and associated CIE diagram indicated that the as-synthesized and annealed NSs produce blue color. The investigated antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus implies the superior biological activity of the as-synthesized and annealed samples at 200 °C. The annealing enhances photoluminescence and antimicrobial activities of ZnSe NSs. The enhanced luminscence properties of ZnSe NSs make them suitable for preparing more efficient blue LEDs and lasers for medical applications. The as-synthesized and annealed ZnSe NSs are found effective against the growth of microorganisms, and sustaining this tendency for 1 week provides a strong basis for the development of new drugs against bacterial infections for supporting the pharmaceutical industry.

Focused review on dual inhibition of quorum sensing and efflux pumps: A potential way to combat multi drug resistant Staphylococcus aureus infections

Staphylococcus aureus is a common cause of skin infections, food poisoning and severe life-threatening infections. Methicillin-Resistant Staphylococcus aureus (MRSA) is known to cause chronic nosocomial infections by virtue of its multidrug resistance and biofilm formation mechanisms. The antimicrobial resistance owned by S. aureus is primarily due to efflux pumps and formation of microbial biofilms. These drug resistant, sessile and densely packed microbial communities possess various mechanisms including quorum sensing and drug efflux. Quorum sensing is a cooperative physiological process which is used by bacterial cells for social interaction and signal transduction in biofilm formation whereas efflux of drugs is derived by efflux pumps. Apart from their significant role in multidrug resistance, efflux pumps also contribute to transporting cell signalling molecules and due to their occurrence; we face the frightening possibility that we will enter the pre-antibiotic era soon. Compounds that modulate efflux pumps are also known as efflux pump inhibitors (EPI's) that act in a synergistic manner and potentiate the antibiotics efficacy which has been considered as a promising approach to encounter bacterial resistance. EPIs inhibit the mechanism of drug efflux s as well as transport of quorum sensing signalling molecules which are the supreme contributors of miscellaneous virulence factors. This review presents an accomplishments of the recent investigations allied to efflux pump inhibitors against S. aureus and also focus on related correspondence between quorum sensing system and efflux pump inhibitors in terms of S. aureus and MRSA biofilms that may open a new avenue for controlling MRSA infections.

Green synthesis and characterization of silver nanoparticles using Pteris vittata extract and their therapeutic activities

The bacterial infections have been substantially increasing with higher mortality and new regimens required for their management. The present work deals with the green synthesis of silver nanoparticles (AgNPs) using leaf extract of Pteris vittata at pH 9.0. The AgNPs showed a single absorption peak at 407 nm. The morphology of AgNPs was found to be spherical in shape analyzed by scanning electron micrographs. The X-ray diffraction studies revealed the face-centered cubic structure of AgNPs with a 17-nm average crystallite size. They showed the antimicrobial activity against Pseudomonas aeruginosa, and the cell growth was completely ceased at the minimum inhibitory concentration (MIC); 100 μg/mL, with rapidly decreased cell viability. This bactericidal effect was due to the enhancement of cell permeability caused by cell disruption. The AgNPs lead to show a promising antiquorum-sensing activity by inhibition of toxin protease and pyocyanin in P. aeruginosa by 88% and, 94% respectively, at the sub-MIC concentration (0.25× MIC). These results conclude that the green synthesis of AgNPs shows a promising antimicrobial and antivirulence activity against P. aeruginosa.

Mycopharmaceuticals and Nutraceuticals: Promising Agents to Improve Human Well-Being and Life Quality

Fungi, especially edible mushrooms, are considered as high-quality food with nutritive and functional values. They are of considerable interest and have been used in the synthesis of nutraceutical supplements due to their medicinal properties and economic significance. Specific fungal groups, including predominantly filamentous endophytic fungi from Ascomycete phylum and several Basidiomycetes, produce secondary metabolites (SMs) with bioactive properties that are involved in the antimicrobial and antioxidant activities. These beneficial fungi, while high in protein and important fat contents, are also a great source of several minerals and vitamins, in particular B vitamins that play important roles in carbohydrate and fat metabolism and the maintenance of the nervous system. This review article will summarize and discuss the abilities of fungi to produce antioxidant, anticancer, antiobesity, and antidiabetic molecules while also reviewing the evidence from the last decade on the importance of research in fungi related products with direct and indirect impact on human health.

Screening and characterization of a novel Antibiofilm polypeptide derived from filamentous Fungi

In the present study, 120 fungal isolates were locally isolated from soil and selected according to their ability to antimicrobial activity. Then, selected isolates were tested for their ability to prevent biofilm formation and only one isolate (A01) showed an antibiofilm effect. The isolate A01 identified as Aspergillus tubingensis by sequencing of the 18S ITS region and a segment of β-tubulin gene. Then, 5 fractions were prepared from the culture filtrate of A. tubingensis A01 using the ultrafiltration technique to find active polypeptide fraction. The experiments revealed that one of them had an antibiofilm activity. The MALDI-TOF/MS analyses demonstrated that this polypeptide composed of 92 amino acids and had a molecular mass of 10,087 Da. The sequence alignment showed homology with hypothetical protein (OJI81679.1). The gene coding for this polypeptide consisting of 279 nucleotides, herein we called astucin, was cloned and sequenced from A. tubingensis A01 to confirm results. The MIC of the purified polypeptide was 32 m/L and 128 μg/mL and the MBIC was 2 and 8 μg/mL against Staphylococcus aureus and MRSA, respectively. The results demonstrated that the antimicrobial and antibiofilm activity of astucin, together with its lack of cytotoxicity, makes it an alternative for application in medicine. SIGNIFICANCE: Antibiotic resistance is a global problem and the emergence of antibiotic resistant bacteria reduce the effect the current treatment approaches. In this context, antimicrobial peptides stand out as potentional agents to combat bacterial infection especially, biofilm related infections. Importantly, this study have greatly considered our understanding for fungal derived antibiofilm polypeptides. In this study, traditional selection method combined with crystal violet assay is used to investigate antibiofilm polypeptides. We identified antibiofilm polypeptides purified from A. tubingensis A01. This protein shows antimicrobial and antibiofilm activity against S. aureus.

Ouabain potentiates the antimicrobial activity of aminoglycosides against Staphylococcus aureus

Background

Staphylococcus aureus is a notorious pathogen which often causes nosocomial and community attained infections. These infections steadily increased after evolving the resistance due to indecorous practice of antibiotics and now become a serious health issue. Ouabain is a Na⁺/K⁺-ATPase inhibitor that leads to increase the heart contraction in patients with congestive heart failure.

Methods

In the present study, in vitro antimicrobial effect of ouabain together with aminoglycosides was determined against clinical and non-clinical S. aureus strains. Using checkerboard, Gentamycin uptake and biofilm assays, we analysed he interactions of ouabain with aminoglycosides.

Results

Ouabain induced the staphylocidal potency of aminoglycosides by remarkably reducing the MIC of gentamycin (GEN) by 16 (0.25 μg/mL), 8 folds (0.5 μg/mL) amikacin (AMK); and 16 folds (1.0 μg/mL) with kanamycin (KAN), compared to their individual doses. OBN severely reduced cell viability within 60 min with GEN (1 μg/mL), KAN (2 μg/mL) and 90 min with AMK (1 μg/mL). This bactericidal effect was enhanced due to GEN uptake potentiated by 66% which led to increase the cell permeability as revealed by leakage of bacterial ATP and nitrocefin assay. The biofilm adherence disrupted by 80 and 50% at 5 mg/mL and 1.5 mg/mL OBN and 50 and 90% biofilm formation was inhibited at 5 mg/mL (MBIC₅₀) and 10 mg/mL (MBIC₉₀), respectively. Moreover, OBN with GEN further induced biofilm inhibition by 67 ± 5% at pH 7.0.

Conclusions

Taken together, we established that OBN synergizes the antimicrobial activity of aminoglycosides that induces cell killing due to intracellular accumulation of GEN by disturbing cell homeostasis. It may be proven an effective approach for the treatment of staphylococcal infections.