Chlamydomonas reinhardtii-expressed multimer of Bacteriocin LS2 potently inhibits the growth of bacteria

Bacteriocin LS2 was isolated from the Lactobacillus salivarius BGHO1 strain in 2012. Since then, its antibacterial activity has not been examined. Here, Chlamydomonas reinhardtii was used to express a C-terminal hemagglutinin (HA) and 6×His double tagged three repeats of Bacteriocin LS2 (3×Bacteriocin LS2). 3×Bacteriocin LS2 expression was stable following passaging in C. reinhardtii cells for six months and its yield accounted for 0.28% of total soluble proteins of the host cells. C. reinhardtii-derived 3×Bacteriocin LS2 inhibited the growth of four tested bacteria of both gram-positive and gram-negative with minimum inhibitory concentration (MIC) values between 75 and 90 μg/mL, indicating that this peptide is more potent than other bacteriocins like nesin and bacteriocin MA047A which have a MIC beyond 165 μg/mL in general. The recombinant 3×Bacteriocin LS2 maintained high stability over a wide range of temperature and pHs, showed tolerance to proteases, exhibited low hemolytic activity against rabbit erythrocytes and low cytotoxicity to human embryonic kidney 293 T (HEK 293 T) cells. In addition, C. reinhardtii-derived 3×Bacteriocin LS2 penetrated cell membranes and destroyed the morphology of targeted bacterial cells to different extents. In summary, our study shows that C. reinhardtii can be used as a platform for the production of active Bacteriocin LS2.     

Peptides in the hemolymph of Hermetia illucens larvae completely inhibit the growth of Klebsiella pneumonia in vitro and in vivo

Extensive use of antibiotics has caused the microbial resistance to rise drastically within the last few decades, and new approaches are therefore needed to develop effective antibacterial substances. In this study, we identified peptide in the hemolymph of Hermetia illucens larvae using reverse-phase chromatography, HPLC and Nano-LC-ESI-MS/MS system. We investigated the antibacterial effect of HP/F9 peptides against Klebsiella pneumoniae in vitro and in vivo. The peptide effectively inhibited the growth of K. pneumoniae in vitro and completely removed K. pneumoniae from the lungs of mice. Importantly, peptides (22,000 Da, HP/F9) successfully reduced lung inflammation upon K. pneumoniae infection. These results indicate that the HP/F9 peptide from H. illucens larva can effectively protect the mouse from K. pneumoniae infection. HP/F9 could be a new candidate for the development of effective antibacterial substance.     

N-acetyl-cysteine mediates protection against Mycobacterium avium through induction of human β-defensin-2 in a mouse lung infection model

Mycobacterium avium complex is a causative organism for refractory diseases. In this study, we examined the effects of N-acetyl-cysteine on M. avium infection in vitro and in vivo. N-acetyl-cysteine treatment suppressed the growth of M. avium in A549 cells in a concentration-dependent manner. This effect was related to the induction of the antibacterial peptide human β-defensin-2. In a mouse model, N-acetyl-cysteine treatment significantly reduced the number of bacteria in the lungs and induced murine β-defensin-3. In interleukin-17-deficient mice, the effects of N-acetyl-cysteine disappeared, indicating that these mechanisms may be mediated by interleukin-17. Moreover, an additional reduction in bacterial load was observed in mice administered N-acetyl-cysteine in combination with clarithromycin. Our findings demonstrate the potent antimycobacterial effects of N-acetyl-cysteine against M. avium by inducing antimicrobial peptide, suggesting that N-acetyl-cysteine may have applications as an alternative to classical treatment regimens.     

Complete green synthesis of silver-nanoparticles applying seed-borne Penicillium duclauxii

Seed-borne fungus Penicillium duclauxii was examined in this study to investigate its capability of synthesizing silver nanoparticles (Ag-NPs). In vitro experiments were conducted using corn-grain contaminating fungal isolate. Ag-NPs detection and characterization were assayed by the aid of spectroscopic techniques. Spectroscopy (energy dispersive), X-ray diffraction, transmission electron-microscope and optical absorption dimensions were employed.Ag-NPs with biosynthesized were used to test invitro against Bipolaris sorghicola; the cause of target leaf spot disease on sorghum plants. The myco-synthesis of Ag NPs using Penicillium duclauxii was proved in this study. Moreover, Bipolaris sorghicola was successfully inhibited by such Ag NPs in vitro.     

Antimicrobial effect of different herbal plant extracts against different microbial population

This study evaluates the antimicrobial effects of ethanolic extract of five herbal plants; Guava (Psidium guajava), Sage (Salvia officinalis), Rhamnus (Ziziphusspina Christi), Mulberry (Morusalba L.), and Olive (Oleaeuropaea L) leaves against several microbial population representing Gram positive, Gram negative and Mollicutes; S. aureus, E. coli, Pasteurella multocida, B. cereus, Salmonella Enteritidis and M. gallisepticum using standard agar disc diffusion technique and minimal inhibitory concentration (MIC). Different extracts reveal variable results against the microorganism under study. All extracts have no antibacterial potency for Mycoplasma gallisepticum except Psidium guajava. The results of minimal inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) of the extracts against the six bacteria ranged from 625 to 5000 μg/ml. The used herbal extract could inhibit the selected microorganism under study with variable minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC).     

Synergistic activity of melittin with mupirocin: A study against methicillin-resistant S. Aureus (MRSA) and methicillin-susceptible S. Aureus (MSSA) isolates

Methicillin-Resistant Staphylococcus aureus (MRSA) biofilms are involved in various nosocomial infections, being in the limelight of academic research. The current study aimed to determine the antimicrobial effects of melittin on planktonic and biofilm forms of S. aureus. Following the identification of MRSA and SCCmec types (using PCR method), Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), and fractional inhibitory concentration index (FICi), for melittin and mupirocin were determined by broth microdilution assay. Melittin anti-biofilm activity was determined, using a microtiter-plate test (MtP) and scanning electron microscope (SEM) methods. The quorum sensing inhibitory activity of ½ MIC melittin was examined using a quantitative real-time RT-PCR method, and melittin cytotoxicity on Vero cells was examined by tetrazolium-based colorimetric (MTT) test. The Results of our study showed that Geometric means of MIC values of the melittin and mupirocin were 4.4 and 14.22 μg/ml respectively. The geometric mean of the FICi for both melittin-mupirocin was 0.75. No S. aureus biofilm was formed and hld gene (as a biofilm regulator) expression down-regulated. It seems that melittin can be useful in the treatment of S. aureus infections (especially MRSA) by reducing the hld expression. Furthermore, synergistic growth-inhibitory effects of mupirocin with melittin could be considered as a promising approach in the treatment of MRSA isolates.     

Screening of Indonesian peat soil bacteria producing antimicrobial compounds

The development and world-wide spread of multidrug-resistant (MDR) bacteria have a high concern in the medicine, especially the extended-spectrum of beta-lactamase (ESBL) producing Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). There are currently very limited effective antibiotics to treat infections caused by MDR bacteria. Peat-soil is a unique environment in which bacteria have to compete each other to survive, for instance, by producing antimicrobial substances. This study aimed to isolate bacteria from peat soils from South Kalimantan Indonesia, which capable of inhibiting the growth of Gram-positive and Gram-negative bacteria. Isolates from peat soil were grown and identified phenotypically. The cell-free supernatant was obtained from broth culture by centrifugation and was tested by agar well-diffusion technique against non ESBL-producing E. coli ATCC 25922, ESBL-producing E. coli ATCC 35218, methicillin susceptible Staphylococcus aureus (MSSA) ATCC 29,213 and MRSA ATCC 43300. Putative antimicrobial compounds were separated using SDS-PAGE electrophoresis and purified using electroelution method. Antimicrobial properties of the purified compounds were confirmed by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). In total 28 isolated colonies were recovered; three (25PS, 26PS, and 27PS) isolates produced proteins with strong antimicrobial activities against both reference strains. The substance of proteins from three isolates exerted strong antimicrobial activity against ESBL-producing E. coli ATCC 35,218 (MIC = 2,80 µg/mL (25PS), 3,76 µg/mL (26PS), and 2,41 µg/mL (27PS), and MRSA ATCC 43,300 (MIC = 4,20 µg/mL (25PS), 5,65 µg/mL (26PS), and 3,62 µg/mL (27PS), and also had the ability bactericidal properties against the reference strains. There were isolates from Indonesian peat which were potentials sources of new antimicrobials.     

Design and synthesis of amphiphilic 2-hydroxybenzylphosphonium salts with antimicrobial and antitumor dual action

Here we report the synthesis and biological evaluation of a series of new 2-hydroxybenzylphosphonium salts (QPS) with antimicrobial and antitumor dual action. The most active compounds exhibit antimicrobial activity at a micromolar level against Gram-positive bacteria Sa (ATCC 209p and clinical isolates), Bc (1–2 μM) and fungi Tm and Ca, and induced no notable hemolysis at MIC. The change in nature of substituents of the same length led to a drastic change of biological activity. Self-assembly behavior of the octadecyl and oleyl derivatives was studied. QPS demonstrated self-assembly within the micromolar range with the formation of nanosized aggregates capable of the solubilizing hydrophobic probe. The synthesized phosphonium salts were tested for cytotoxicity. The most potent salt was active against on M−Hela cell line with IC₅₀ on the level of doxorubicin and good selectivity. According to the cytofluorimetry analysis, the salts induced mitochondria-dependent apoptosis.     

Novel isoniazid embedded triazole derivatives: Synthesis,antitubercular and antimicrobial activity evaluation

In the present study, a series of new isoniazid embedded triazole derivatives have been synthesized. These compounds were evaluated for their in vitro antitubercular and antimicrobial activities. Among the screened compounds, six have exhibited potent antitubercular activity against Mycobacterium tuberculosis H37Rv strain with MIC value 0.78 μg/mL, whereas, three compounds have displayed activity with MIC value ranging from 1.56 to 3.125 μg/mL. The cytotoxicity of the active compounds was studied against RAW 264.7 cell line by MTT assay and no toxicity was observed even at 25 μg/mL concentration. The five compounds have displayed good antimicrobial activities. Molecular docking have been performed against mycobacterial InhA enzyme to gain an insight into the plausible mechanism of action which could pave the way for our endeavor to identify potent antitubercular candidates. We believe that further optimization of these molecules may lead to potent antitubercular agents.