SCREENING OF PUTATIVE THERAPEUTIC CANDIDATES IN SUPERBUG (STAPHYLOCOCCUS AUREUS): A SYSTEMATIC IN SILICO APPROACH

ABSTRACTObjective: Staphylococcus aureus, a superbug and antibiotic resistant pathogen, is one of the most infection causing organism, ranging from skinallergies to severe lethal conditions. The prolonged use of different antibiotics and lack of optimal treatment over the antibiotic resistant species, ledto the identification of new, better and promising therapeutic candidates. Methods: A systematic in silico filtration process was employed, which includes subtractive channels and reverse vaccinology techniques. Results: Here, we report 12 possible drug targets and two vaccine candidates based on essentiality, non-human homolog, virulent and localization,commonly in all the strains. Further characterization studies such as pathway analysis, chokepoint and structure prediction revealed, two proteinsas the best drug targets one being novel and the other druggable. Only one protein has shown the characteristic feature of vaccine candidate, havingantigenic property and an IgG binding domain. Conclusion: Two best drug targets were commonly identified in all the strains of S. aureus namely UDP-N-acetylmuramoyl-L-alanyl-D-glutamate--L-lysineligase (MurE) and cell division protein FtsA, whereas the best common vaccine candidate includes Peptidoglycan binding protein. The therapeutic candidatesreported in the present study might facilitate screening of new and better antimicrobial compounds, for an optimal treatment of S. aureus infections.Keywords: Staphylococcus aureus, Drug target, Vaccine candidates, Subtractive proteomics, Reverse vaccinology

PREDICTION OF PROMISCUOUS EPITOPE STUDIES OF SPA ANTIGEN IN STAPHYLOCOCCUS AUREUS: AN INSIGHT ON PEPTIDE-BASED VACCINE

Objective: Owing to the difficulty in providing drug therapies against Methicillin-resistant Staphylococcus aureus (MRSA), the development of an effective and promising vaccine is an immense challenge in combatingMRSA infections. The present work focuses on the development of a peptide-based vaccine, by identifying the epitopes from SPA antigen.Methods: The epitopes were identified based on different properties, such that they are capable of eliciting broadly neutralizing immune responses. The identified epitopes were subjected for peptide docking using Glide and antibody-antigen docking using ClusPro.Results: By in silico approach two epitopes NLNEEQRNG†and LKDDPSQSAN†were identified for SPA protein with sequence lengths of nine and ten respectively. The least energy for the peptide docking was observed for NLNEEQRNG sequence and the amino acid residues of this peptide share similar interaction with antibody-antigen docking.Conclusion: Based on the properties and docking studies the best-ranked epitope sequence is ‘NLNEEQRNG'. Further studies on this peptide sequence might be helpful for alternative therapy of MRSA infections.Keywords: Epitope, SPA antigen, IgG antibody, Docking studie

MrdH, a Novel Metal Resistance Determinant of Pseudomonas putida KT2440, Is Flanked by Metal-Inducible Mobile Genetic Elements▿ †

We report here the identification and characterization of mrdH, a novel chromosomal metal resistance determinant, located in the genomic island 55 of Pseudomonas putida KT2440. It encodes for MrdH, a predicted protein of ∼40 kDa with a chimeric domain organization derived from the RcnA and RND (for resistance-nodulation-cell division) metal efflux proteins. The metal resistance function of mrdH was identified by the ability to confer nickel resistance upon its complementation into rcnA mutant (a nickel- and cobalt-sensitive mutant) of Escherichia coli. However, the disruption of mrdH in P. putida resulted in an increased sensitivity to cadmium and zinc apart from nickel. Expression studies using quantitative reverse transcription-PCR showed the induction of mrdH by cadmium, nickel, zinc, and cobalt. In association with mrdH, we also identified a conserved hypothetical gene mreA whose encoded protein showed significant homology to NreA and NreA-like proteins. Expression of the mreA gene in rcnA mutant of E. coli enhanced its cadmium and nickel resistance. Transcriptional studies showed that both mrdH and mreA underwent parallel changes in gene expression. The mobile genetic elements Tn4652 and IS1246, flanking mrdH and mreA were found to be induced by cadmium, nickel, and zinc, but not by cobalt. This study is the first report of a single-component metal efflux transporter, mrdH, showing chimeric domain organization, a broad substrate spectrum, and a location amid metal-inducible mobile genetic elements