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

Evaluation of probiotic potential of Bacillus spp. isolated from the digestive tract of freshwater fish Labeo calbasu (Hamilton, 1822)

The probiotic use in aquaculture helps to improve the survival, growth and health of fish as it is a sustainable aquaculture practice. In the present study, Bacillus spp. were isolated from the digestive tract of freshwater fish, Labeo calbasu towards the assessment of their probiotic potential. Based on the preliminary screening on 64 isolates obtained from the digestive tract of L. calbasu, only the Bacillus strains FS1, FC3 and FC6 were selected by using Bacillus selective media (Himedia) for their probiotics characterization. The biosafety assay confirmed that the isolates were not pathogenic to the host fish. Further, the selected isolates Viz; FS1, FC3 and FC6 were evaluated for probiotic properties. These strains were able to survive in acidic and alkaline conditions, higher tolerance to bile salt, high surface hydrophobicity to solvents, and they were found to tolerate in gastric juice. All the three isolates have exhibited notable amylase, proteolytic, lipase activity and susceptibility to various antibiotics. Their antagonistic activity was assessed against the fish pathogens; Aeromonas hydrophila (KX756709), A. veronii (KX688046), Acinetobacter junii (KX756708), A. tandoii (KX775222) Acinetobacter sp. (KX775221), and Pseudomonas stutzeri (KX721473) that were isolated from the naturally infected fish, Dawkinsia filamentosa. Among the three isolates, the FC6 exhibited a good antagonistic activity against three fish pathogens Viz; Aeromonas hydrophila, Acinetobacter sp. and Acinetobacter tandoii; FS1 and FC3 strains did not show any activity against the pathogens. Time killing kinetics assay also revealed that pathogens treated sample attained stationary phase quickly when compared to the control. Only the FC6 isolate had exhibited positive results for biofilm formation assay. All the three isolates did not exhibit any haemolytic activity. The isolated species were identified and confirmed on the basis of their colony morphology, biochemical characteristics and 16S rRNA sequencing. The probiotic strains, FS1, FC3 and FC6 were identified to be Bacillus subtilis (KX756706), Bacillus cereus (KX756707) and Bacillus amyloliquefaciens (KX775224) respectively. Based on the presently observed characteristic features, it is concluded that the FC6 strain, Bacillus amyloliquefaciens found in the digestive tract of L. calbasu could form a potential probiotic candidate. Keywords: Bacillus, Probiotic, Survival, Antibiotic resistance, Fish pathogens, Antagonistic activity, Labeo calbas

Overexpression of circulating miRNA-21 and miRNA-146a in plasma samples of breast cancer patients

210-214Breast cancer is the second most common malignant disease affecting Indian women and is the leading cause of cancer-related mortality. MicroRNAs (miRNAs) are remarkably stable in blood, which makes them novel and promising biomarkers for cancer detection and diagnosis. In this study, we investigated whether expression levels of circulating specific miRNAs, such as microRNA-21 (miR-21) and microRNA-146a (miR-146a) could be used as potential biomarkers in plasma of breast cancer patients and healthy individuals. We compared the expression levels of breast cancer associated specific miRNAs — miR-21 and miR-146a in plasma samples of histopathologically reported 14 patients (aged 35-61 yrs) with breast cancer and an additional 8 healthy volunteers (aged 35-54 yrs). The miRNA expression level was determined by TaqMan quantitative PCR (qPCR) assay. The miRNA expression level of each sample was normalized to that of miR-16 as reference and expressed as relative expression (2-Ct). Our results showed that the circulating level of miR-21 and miR-146a were significantly higher in plasma samples of breast cancer patients, when compared to those of healthy controls (p<0.0004 and p<0.005, respectively). Thus, analyzing expression of miR-21 and miR-146a from plasma samples of breast cancer patients might be useful in the diagnosis of breast cancer. However, further studies with larger number of patients and control individuals are needed to confirm the results. </span