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 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.


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 microg/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.


CONCLUSIONS
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.
Perumal Samy
R
R
Venom and Toxin Research Programme, Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore-117597. antrps@nus.edu.sg
Pachiappan
A
A
Gopalakrishnakone
P
P
Thwin
Maung M
MM
Hian
Yap E
YE
Chow
Vincent T K
VT
Bow
Ho
H
Weng
Joseph T
JT
D000818:Animals; D016957:Burkholderia pseudomallei / Q000187:drug effects* / Q000302:isolation & purification; D003439:Crotoxin / Q000302:isolation & purification / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D006801:Humans; D008554:Melioidosis / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010741:Phospholipases A / Q000302:isolation & purification / Q000494:pharmacology; D054467:Phospholipases A2; D011506:Proteins / Q000302:isolation & purification / Q000494:pharmacology; D018805:Sepsis / Q000382:microbiology; D012910:Snake Venoms / Q000201:enzymology / Q000494:pharmacology*; D014757:Viper Venoms
D011506:Proteins; D012910:Snake Venoms; D014757:Viper Venoms; C094035:daboiatoxin; D003439:Crotoxin; D010741:Phospholipases A; D054467:Phospholipases A2