In vitro antimicrobial activity of natural toxins and animal venoms tested against Burkholderia pseudomallei

BACKGROUND: Burkholderia pseudomallei are the causative agent of melioidosis. Increasing resistance of the disease to antibiotics is a severe problem in treatment regime and has led to intensification of the search for new drugs. Antimicrobial peptides are the most ubiquitous in nature as part of the innate immune system and host defense mechanism. METHODS: Here, we investigated a group of venoms (snakes, scorpions and honey bee venoms) for antimicrobial properties against two strains of Gram-negative bacteria Burkholderia pseudomallei by using disc-diffusion assay for in vitro susceptibility testing. The antibacterial activities of the venoms were compared with that of the isolated L-amino acid oxidase (LAAO) and phospholipase A(2 )(PLA(2)s) enzymes. MICs were determined using broth dilution method. Bacterial growth was assessed by measurement of optical density at the lowest dilutions (MIC 0.25 mg/ml). The cell viability was measured using tetrazolium salts (XTT) based cytotoxic assay. RESULTS: The studied venoms showed high antimicrobial activity. The venoms of C. adamanteus, Daboia russelli russelli, A. halys, P. australis, B. candidus and P. guttata were equally as effective as Chloramphenicol and Ceftazidime (30 μg/disc). Among those tested, phospholipase A(2 )enzymes (crotoxin B and daboiatoxin) showed the most potent antibacterial activity against Gram-negative (TES) bacteria. Naturally occurring venom peptides and phospholipase A(2 )proved to possess highly potent antimicrobial activity against Burkholderia pseudomallei. The XTT-assay results showed that the cell survival decreased with increasing concentrations (0.05–10 mg/mL) of Crotalus adamanteus venom, with no effect on the cell viability evident at 0.5 mg/mL. CONCLUSION: This antibacterial profile of snake venoms reported herein will be useful in the search for potential antibacterial agents against drug resistant microorganisms like B. pseudomallei

Investigating the therapeutic potential of herbal leads against drug resistant <i>Listeria monocytogenes</i> by computational virtual screening and <i>in vitro</i> assays

<div><p><i>Listeria monocytogenes</i>, a Gram-positive opportunistic food-borne pathogen, naturally resistant to many antibiotics and acquired resistance may be a concern in the nearer future. Hence, there is a scope for screening of novel therapeutic agents and drug targets, toward the treatment of fatal listeria infections. The SecA homologs, SecA1 and SecA2 are the essential components of the general secretion (Sec) pathway, a specialised protein export system, present in <i>L. monocytogenes</i>. This study evaluates the use of botanicals against <i>L. monocytogenes</i> MTCC 1143 by considering SecA proteins as probable drug targets by high-throughput screening approaches. The 3D structure of SecA proteins with good stereochemical validity was generated by comparative modelling. The druglikeness and pharmacokinetic properties of 97 phytoligands identified through the extensive literature survey were predicted for druglikeness and ADMET properties. The inhibitory properties of best candidates were studied by molecular docking. The effect of the selected candidate molecules were further analysed <i>in vitro</i> well diffusion and cell aggregation assays. The antibiotic sensitivity profiling applied to <i>L. monocytogenes</i> MTCC 1143 using clinically relevant antibiotics showed that the bacteria became drug resistant to many tested antibiotics. The virtual screening suggested that .05 M cinnamic aldehyde from <i>Cinnamomum camphora</i> and 1, 2-Epoxycyclododecane from <i>Cassia auriculata</i> were identified as potential SecA inhibitors. The well diffusion assays suggested that the selected herbal substances have antibacterial activities. Further, preliminary validation suggested that incorporation of cinnamic aldehyde and methanolic or ethyl acetate extract of <i>C. auriculata</i> in broth medium shows growth reduction, misassembly and cell aggregation. This indicates the inhibition of SecA targets.</p></div

Gene microarray analyses of daboia russelli russelli daboiatoxin treatment of THP-1 human macrophages infected with burkholderia pseudomallei

© 2015 Bentham Science Publishers. Burkholderia pseudomallei is the causative agent of melioidosis and represents a potential bioterrorism threat. In this study, the transcriptomic responses of B. pseudomallei infection of a human macrophage cell model were investigated using whole-genome microarrays. Gene expression profiles were compared between infected THP-1 human monocytic leukemia cells with or without treatment with Daboia russelli russelli daboiatoxin (DRRDbTx) or ceftazidime (antibiotic control). Microarray analyses of infected and treated cells revealed differential upregulation of various inflammatory genes such as interleukin-1 (IL-1), IL-6, tumor necrosis factor-alpha (TNF-a), cyclooxygenase (COX-2), vascular endothelial growth factor (VEGF), chemokine C-X-C motif ligand 4 (CXCL4), transcription factor p65 (NF-kB); and several genes involved in immune and stress responses, cell cycle, and lipid metabolism. Moreover, following DRR-DbTx treatment of infected cells, there was enhanced expression of the tolllike receptor 2 (TLR-2) mediated signaling pathway involved in recognition and initiation of acute inflammatory responses. Importantly, we observed that highly inflammatory cytokine gene responses were similar in infected cells exposed to DRR-DbTx or ceftazidime after 24 h. Additionally, there were increased transcripts associated with cell death by caspase activation that can promote host tissue injury. In summary, the transcriptional responses during B. pseudomallei infection of macrophages highlight a broad range of innate immune mechanisms that are activated within 24 h post-infection. These data provide insights into the transcriptomic kinetics following DRR-DbTx treatment of human macrophages infected with B. pseudomallei

ETS2 regulating neurodegenerative signaling pathway of human neuronal (SH-SY5Y) cells exposed to single and repeated low-dose sarin (GB)

10.1021/tx8003467Chemical Research in Toxicology226990-99