ß-lactamase inhibitory potential of kalafungin from marine Streptomyces in Staphylococcus aureus infected zebrafish.

ß-lactamase inhibitors are potent synergistic drugs to deteriorate the multidrug-resistant bacteria. Here, we report the ß-lactamase inhibitory ability of kalafungin isolated from a marine sponge derived Streptomyces sp. SBRK1. The IC50 value of the kalafungin was calculated as 225.37 ± 1.95 µM against ß-lactamase. The enzyme kinetic analysis showed the Km value of 3.448 ± 0.7 µM and Vmax value of 215.356 ± 8 µM/min and the inhibition mechanism was identified as uncompetitive type. Along with the antibacterial activity, the cell surface analysis of kalafungin treated Staphylococcus aureus cells revealed destruction of cell membrane in response to ß-lactamase inhibition. Molecular docking studies have confirmed the binding property of kalafungin against ß-lactamase with two hydrogen bonds. In vivo efficacy studies in the zebrafish model by green fluorescent protein expressing S. aureus infection, survival, safety and behavioral profile were reported. The toxicity and anti-infection revealed that the compound was evidently active and safe to all organs. In conclusion, this is the first report on kalafungin with ß- lactamase inhibition and suggests that kalafungin may useful for synergic antibacterial therapy with ß-lactam drugs to overcome ß-lactamase-based resistance of any bacterial pathogens.

Cell wall distraction and biofilm inhibition of marine Streptomyces derived angucycline in methicillin resistant Staphylococcus aureus.

The emergence of life threatening antibiotic resistant pathogens and its associated mortality and morbidity necessitates many new antibiotics from diverse ecological habitats. Marine sponge associated microbes are promising to provide such antimicrobial compounds. In the present study, we report antibacterial and anti-biofilm potential of the angucycline antibiotic 8-O-metyltetrangomycin from Streptomyces sp. SBRK2 isolated from a marine sponge of Gulf of Mannar, Rameswaram, India. Our screening program to tackle methicillin-resistant Staphylococcus aureus (MRSA) drug resistance from marine sponge associated actinobacteria yielded the bioactive strain SBRK2. Based on 16S rRNA gene phylogenetic analysis the isolate was found to closely related with Streptomyces longispororuber NBRC 13488T. In vitro production by agar plate fermentation, solvent based extraction, TLC, HPLC purification and LC-MS based de-replication revealed the bioactive compound as 8-O-metyltetrangomycin. The antibacterial minimum inhibitory concentrations against MRSA was identified as 2 µg/mL. Sub-inhibitory concentration of the compound 8-O-metyltetrangomycin reduced the biofilm formation of S. aureus ATCC25923 and increased the cell surface hydrophobicity index. Scanning electron microscopic observation of the sub-inhibitory concentration exposure revealed a wrinkled membrane surface and slight cellular damage shows the cell wall distracting property of the compound. Zebrafish embryo based toxicity assays exhibited 100 µg/mL of compound as maximal non-lethal concentration which had demonstrated the positive relationship in safety index. The angucycline compound 8-O-metyltetrangomycin could be a potential candidate for the development of anti-biofilm agents against drug resistant pathogens.