Potential anti-leptospiral compound, leptomycin B from marine Streptomyces indiaensis MSU5: taxonomy, fermentation, compound isolation, in vitro and in vivo efficacy

Abstract

Leptospirosis is a worldwide reemerging tropical zoonotic disease with symptoms of mild febrile illness to more severe multiple organ failure caused by pathogenic leptospiral strains. There was no effective antibiotic for treating leptospirosis. Here, the anti-leptospiral potential of marine actinobacterial compound from Streptomyces indiaensis MSU5 isolated from Manakudy marine sediment, Tamil Nadu, India was evaluated. The potential actinobacterial strain was identified by phenotypic, cell wall, 16S rRNA gene sequence and phylogenetic analysis. In vitro anti-leptospiral activity of the actinobacterial compound was determined using broth microdilution test against various serovars of Leptospira with different concentration ranging from 15.625 to 500 µg/ml. Mass production of anti-leptospiral compound was carried out in agar surface fermentation with optimized condition and purified by preparative TLC. The purified fraction of anti-leptospiral compound named as MSU5-1, and it was confirmed by microdilution test. Remarkably, the compound MSU5-1 showed minimum inhibitory concentration of 62.5 µg/ml and minimum bactericidal concentration of 125 µg/ml against human pathogenic leptospiral isolate strain N2. The structural elucidation of purified compound was carried out using UV, FT-IR, NMR and LC-MS analysis. The compound MSU5-1 was tentatively identified as leptomycin B (CHO) with molecular weight 541.1 g/mol. Anti-leptospiral activity of compound MSU5-1 exhibited 80% of survival rate in mice model, further it was confirmed by Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) analysis. From the available literature, this is the first report on the marine actinobacterial compound for evaluating both in vitro and in vivo leptospiricidal activity.

Exploration of fish gut‐associated actinobacteria for its antifouling activity

“…Due to the chemical's diluted form, cell-free supernatants made from submerged cultures occasionally showed little to no antibacterial activity, although the solvent extract of the same molecule did. Agar surface fermentation (ASF), which is fairly straightforward but less usually utilized for metabolite production, is a type of solid-state fermentation used to produce AF compounds [18,25,27,28,32].…”

“…A 5 mm diameter agar plug was cut from the ISP2 agar after the incubation time using a well cutter and it was then placed over a nutrient agar plate that had been swabbed with test biofilm bacteria. The plates were incubated at 28 ± 2.0°C for 24 h. The diameter of the inhibitory zone (mm) was measured in triplicate to assess and record AF activity [18].…”

Exploration of Fish Gut Associated Actinobacteria for its Anti-Microbial and Anti-Quorum Sensing Properties

“…The scraped mycelium was also suspended in methanol for extraction of intracellular bioactive compounds. The solvent extracts were concentrated using rotary evaporator and quantified [17].…”