Isolation, characterization, statistical optimization, and application of a novel broad-spectrum capsular depolymerase against Klebsiella pneumoniae from Bacillus siamensis SCVJ30

Abstract

Background: Bacterial resistance is one of the most challenging and emerging public healthcare crisis in the modern era. Along with antibiotic degrading strategies, bacteria also evolved to produce extracellular polymers such as capsular polysaccharide (CPS) which not only provides immune protection but also act as a permeability barrier to antibiotics. The use of therapeutic enzymes alone and in combination with antibiotics has opened a new window for clinicians and researchers. Methods: In the present study, isolation of broad-spectrum capsular depolymerase bacterium was attempted from a number of environmental samples followed by 16SrRNA characterization. Optimization of capsular depolymerase production was performed by the one variable at time (OVAT) method and response surface methodology (RSM). Capsular depolymerase was partially purified using ammonium sulfate saturation method. Capsule stripping effects of depolymerase were analyzed using microscopic visualization of the capsule and antibiotic susceptibility test. Results: Thirty-two capsular depolymerase producing bacteria were isolated in this study and broad-spectrum depolymerase producing Isolate-30 was characterized as Bacillus siamensis SCVJ30 according to the 16srRNA sequencing. Depolymerase production was optimized using OVAT method and RSM. Relatively high yields (1.92 IU/ml) of capsular depolymerase were obtained in a medium containing 1 mg magnesium sulfate, 7 mg peptone and at 9 pH. A 115% increase in capsular depolymerase production was observed under optimal conditions than unoptimized conditions. Microscopic visualization of the capsule and antibiotic susceptibility testing postulates the positive effect of depolymerase on antibiotic effi cacy against Klebsiella pneumoniae. Conclusion: Further characterization of the enzyme will help in developing broad-spectrum depolymerase as a potent therapeutic agent against drug-resistant strains.