Browsing by Author "Durg Vijai Singh"

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Antibiotic Susceptibility, Virulence Pattern, and Typing of Staphylococcus aureus Strains Isolated From Variety of Infections in India
(Frontiers Media S.A., 2019) Shifu Aggarwal; Smrutiti Jena; Sasmita Panda; Savitri Sharma; Benu Dhawan; Gopal Nath; N.P. Singh; Kinshuk Chandra Nayak; Durg Vijai Singh
Staphylococcus aureus is one of the major causes of nosocomial infections. This organism produces powerful toxins and cause superficial lesions, systemic infections, and several toxemic syndromes. A total of 109 S. aureus strains isolated from a variety of infections like ocular diseases, wound infection, and sputum were included in the study. Minimum inhibitory concentration (MIC) was determined against 8 antimicrobials. PCR determined the presence of 16S rRNA, nuc, mecA, czrC, qacA/B, pvl, and toxin genes in S. aureus isolates. Pulse-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), SCCmec, spa-, and agr-typing and serotyping determined the diversity among them. All isolates of S. aureus were resistant to two or more than two antibiotics and generated 32 resistance patterns. These isolates were positive for 16S rRNA and S. aureus-specific nuc gene, but showed variable results for mecA, czrC, and qacA/B and pvl genes. Of the 32 methicillin-resistant S. aureus (MRSA), 13 strains carried SCCmec type V, seven type IV, two type III, and nine carried unreported type UT6. Of the 109 strains, 98.2% were positive for hlg, 94.5% for hla, 86.2% for sei, 73.3% for efb, 70.6% for cna, 30.2% for sea, and 12.8% for sec genes. Serotypes VII and VI were prevalent among S. aureus strains. PFGE analysis grouped the 109 strains into 77 clusters. MLST classified the strains into 33 sequence types (ST) and eight clonal complexes (CCs) of which 12 were singletons, and two belong to new allelic profiles. Isolates showed 46 spa-types that included two new spa-types designated as t14911 and t14912. MRSA and methicillin-susceptible S. aureus (MSSA) isolates were diverse in terms of antibiotic resistance pattern, toxin genotypes, SCCmec types, serotypes and PFGE, MLST, and spa-types. However, few isolates from eye infection and wound infection belong to CC239, ST239, and spa-type t037/t657. The study thus suggests that S. aureus strains are multidrug resistant, virulent, and diverse irrespective of sources and place of isolation. These findings necessitate the continuous surveillance of multidrug-resistant and virulent S. aureus and monitoring of the transmission of infection. © Copyright © 2019 Aggarwal, Jena, Panda, Sharma, Dhawan, Nath, Singh, Nayak and Singh.
Binding efficiencies of carbohydrate ligands with different genotypes of cholera toxin B: Molecular modeling, dynamics and docking simulation studies
(2012) Mobashar Hussain Urf Turabe Fazil; Sunil Kumar; Rohit Farmer; Haushila Prasad Pandey; Durg Vijai Singh
Vibrio cholerae produces cholera toxin (CT) that consists of two subunits, A and B, and is encoded by a filamentous phage CTXΦ. The A subunit carries enzymatic activity that ribosylates ADP, whereas the B subunit binds to monosialoganglioside (GM1) receptor in epithelial cells. Molecular analysis of toxigenic V. cholerae strains indicated the presence of multiple ctxB genotypes. In this study, we employed a comparative modeling approach to define the structural features of all known variants of ctxB found in O139 serogroup V. cholerae. Modeling, molecular dynamics and docking simulations studies suggested subtle variations in the binding ability of ctxB variants to carbohydrate ligands of GM1 (galactose, sialic acid and N-acetyl galactosamine). These findings throw light on the molecular efficiencies of pathogenic isolates of V. cholerae harboring natural variants of ctxB in causing the disease, thus suggesting the need to consider ctxB variations when designing vaccines against cholera. © 2011 Springer-Verlag.
Comparative structural analysis of two proteins belonging to quorum sensing system in Vibrio cholerae
(2012) Mobashar Hussain; Turabe Fazil; Sunil Kumar; Naidu Subba Rao; Chandrabose Selvaraj; Sanjeev Kumar Singh; Haushila Prasad Pandey; Durg Vijai Singh
Vibrio cholerae uses quorum sensing communication system to interact with other bacteria and for gauzing environmental parameters. This organism dwells equally well in both human host and aquatic environments. Quorum sensing regulates multitude of activities and is one of the lucrative targets presently pursued for drug design in bacteria to encounter virulence. Histidine phosphotransfer protein LuxU and response regulator LuxO of V. cholerae are known to play important roles in biofilms and virulence machinery. In the present study, we used computational methods to model LuxU and LuxO and simulated the interactions of LuxO and LuxU. Since no structural details of the proteins were available, we employed homology modeling to construct the three-dimensional structures and then performed molecular dynamics simulations to study dynamic behavior of the LuxO and LuxU from V. cholerae. The modeled proteins were validated and subjected to molecular docking analyses. This allowed us to predict the binding modes of the proteins to elucidate probable sites of interference. © 2012 Taylor & Francis.
Effect of methionine-sulfoximine on nitrate uptake and photosynthesis in the cyanobacterium Anabaena doliolum Bharadwaja
(Springer-Verlag, 1988) Durg Vijai Singh; Har Darshan Kumar
l-Methionine-dl-sulfoximine (MSX) stimulated nitrate uptake but inhibited14CO2 fixation and O2 evolution in Anabaena doliolum. Nitrate uptake was inhibited by ammonium (NH4+) in the absence of MSX, but not in the presence of MSX. Glutamine or a derivative of it appears to be the actual negative effector of nitrate utilization. In presence of nitrate, MSX-treated cells of A. doliolum evolve more O2 than do untreated cells. Our results suggest a close relation between photoassimilation of carbon and utilization of nitrogen. © 1988 Springer-Verlag New York Inc.
Homology modelling of a sensor histidine kinase from Aeromonas hydrophila
(2010) Mobashar Hussain Urf Turabe Fazil; Sunil Kumar; Naidu Subbarao; Haushila Prasad Pandey; Durg Vijai Singh
Aeromonas hydrophila has been implicated in extra-intestinal infection and diarrhoea in humans. Targetting unique effectors of bacterial pathogens is considered a powerful strategy for drug design against bacterial variations to drug resistance. The two-component bacterial system involving sensor histidine kinase (SHK) and its response regulators is considered a lucrative target for drug design. This is the first report describing a three-dimensional (3D) structure for SHK of A. hydrophila. The model was constructed by homology modelling using the X-ray structure of PleD-a response regulator-in conjunction with cdiGMP (PDB code 1W25) and HemAT sensor domain (PDB code 1OR4)-a globin coupled sensor. A combination of homology modelling methodology and molecular dynamics (MD) simulations was applied to obtain a reasonable structure to understand the dynamic behaviour of SHK. Homology modelling was performed using MODELLER9v2 software. The structure was relaxed to eliminate bad atomic contacts. The final model obtained by molecular mechanics and dynamics methods was assessed using PROCHECK and VERIFY 3D graph, which confirmed that the final refined model is reliable. Until complete biochemical and structural data of SHK are determined by experimental means, this model can serve as a valuable reference for characterising the protein and could be explored for drug targetting by design of suitable inhibitors. © Springer-Verlag 2009.
Identification of novel sequence types among staphylococcus haemolyticus isolated from variety of infections in India
(Public Library of Science, 2016) Sasmita Panda; Smrutiti Jena; Savitri Sharma; Benu Dhawan; Gopal Nath; Durg Vijai Singh
The aim of this study was to determine sequence types of 34 S. haemolyticus strains isolated from a variety of infections between 2013 and 2016 in India by MLST. The MEGA5.2 software was used to align and compare the nucleotide sequences. The advanced cluster analysis was performed to define the clonal complexes. MLST analysis showed 24 new sequence types (ST) among S. haemolyticus isolates, irrespective of sources and place of isolation. The finding of this study allowed to set up an MLST database on the PubMLST.org website using BIGSdb software and made available at http://pubmlst.org/shaemolyticus/. The data of this study thus suggest that MLST can be used to study population structure and diversity among S. haemolyticus isolates. © 2016 Panda et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Pregnancy - associated human listeriosis: Virulence and genotypic analysis of Listeria monocytogenes from clinical samples
(Microbiological Society of Korea, 2015) Dharmendra Kumar Soni; Durg Vijai Singh; Suresh Kumar Dubey
Listeria monocytogenes, a life-threatening pathogen, poses severe risk during pregnancy, may cause abortion, fetal death or neonatal morbidity in terms of septicemia and meningitis. The present study aimed at characterizing L. monocytogenes isolated from pregnant women based on serotyping, antibiotic susceptibility, virulence genes, in vivo pathogenicity test and ERIC- and REP-PCR fingerprint analyses. The results revealed that out of 3700 human clinical samples, a total of 30 (0.81%) isolates [12 (0.80%) from placental bit (1500), 18 (0.81%) from vaginal swab (2200)] were positive for L. monocytogenes. All the isolates belonged to serogroup 4b, and were + ve for virulence genes tested i.e. inlA, inlC, inlJ, plcA, prfA, actA, hlyA, and iap. Based on the mice inoculation tests, 20 isolates showed 100% and 4 isolates 60% relative virulence while 6 isolates were non-pathogenic. Moreover, 2 and 10 isolates were resistant to ciprofloxacin and cefoxitin, respectively, while the rest susceptible to other antibiotics used in this study. ERIC- and REP-PCR collectively depicted that the isolates from placental bit and vaginal swab had distinct PCR fingerprints except a few isolates with identical patterns. This study demonstrates prevalence of pathogenic strains mostly resistant to cefoxitin and/or ciprofloxacin. The results indicate the importance of isolating and characterizing the pathogen from human clinical samples as the pre-requisite for accurate epidemiological investigations. © 2015, The Microbiological Society of Korea and Springer-Verlag Berlin Heidelberg.
Virulence and genotypic characterization of Listeria monocytogenes isolated from vegetable and soil samples
(BioMed Central Ltd., 2014) Dharmendra Kumar Soni; Major Singh; Durg Vijai Singh; Suresh Kumar Dubey
Background: Listeria monocytogenes, a foodborne pathogen is ubiquitous to different environments including the agroecosystem. The organism poses serious public health problem. Therefore, an attempt has been made to gain further insight to their antibiotic susceptibility, serotypes and the virulence genes. Results: Out of the 10 vegetables selected, 6 (brinjal, cauliflower, dolichos-bean, tomato, chappan-kaddu and chilli), 20 isolates (10%) tested positive for L. monocytogenes. The prevalence of the pathogen in the respective rhizosphere soil samples was 5%. Noticeably, L. monocytogenes was absent from only cabbage, broccoli, palak and cowpea, and also the respective rhizospheric soils. The 30 isolates + ve for pathogenicity, belonged to serogroup 4b, 4d or 4e, and all were positive for inlA, inlC, inlJ, plcA, prfA, actA, hlyA and iap gene except one (VC3) among the vegetable isolates that lacked the plcA gene. ERIC- and REP-PCR collectively revealed that isolates from vegetables and their respective rhizospheric soils had distinct PCR fingerprints. Conclusions: The study demonstrates the prevalence of pathogenic L. monocytogenes in the selected agricultural farm samples. The increase in the number of strains resistant to ciprofloxacin and/or cefoxitin seems to pose serious public health consequences. © 2014 Soni et al.; licensee BioMed Central Ltd.