Abstract
BackgroundBurkholderia 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.MethodsHere, 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 A2 (PLA2s) 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.ResultsThe 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 A2 enzymes (crotoxin B and daboiatoxin) showed the most potent antibacterial activity against Gram-negative (TES) bacteria. Naturally occurring venom peptides and phospholipase A2 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.ConclusionThis antibacterial profile of snake venoms reported herein will be useful in the search for potential antibacterial agents against drug resistant microorganisms like B. pseudomallei.
Highlights
Burkholderia pseudomallei are the causative agent of melioidosis
The antibacterial effects of crotalid, viperid and elapid venoms established in the present study may likely be due to the cyto-toxins and phospholipase A2 enzymes contained in those venoms [37]
According to our results, the 5 different venoms of C. adamanteus, Daboia russelli russelli, P. australis, P. guttata and A. halys exhibited stronger antimicrobial activity against both strains of B. pseudomallei than that shown by the L-amino acid oxidase enzymes of C. adamanteus and B. atrox venoms, suggesting that LAAO activity alone may not be solely responsible for the antibacterial activity of these venoms
Summary
Burkholderia pseudomallei are the causative agent of melioidosis. Gram-negative Burkholderia pseudomallei, the causative agent of melioidosis, are found widely in soil and surface water throughout the tropics. High incidence of melioidosis has been found in Southeast Asia and Northern Australia [1,2]. The majority of adult patients develop acute pulmonary or septicaemic illness with high mortality rates [8], or subacute melioidosis, characterized by multipleabscess formation. In cases of septicaemic melioidosis, which is associated with a vigorous inflammatory cytokine response [9], septic shock continues to be a major cause of morbidity and mortality in patients. Tumor necrosis factor (TNF) is involved in the acquisition of melioidosis, and is related to disease severity [10]
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