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Search Results: 1 - 10 of 702 matches for " Bharathi Sriram "
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Determining the Minimum Inhibitory Concentration of Bacteriophages: Potential Advantages  [PDF]
Aradhana Vipra, Srividya Narayanamurthy Desai, Raghu Patil Junjappa, Panchali Roy, Nethravathi Poonacha, Pallavi Ravinder, Bharathi Sriram, Sriram Padmanabhan
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.32028
Abstract:

The minimum inhibitory concentration (MIC) is the concentration at which an antibacterial agent experiences the complete inhibition of organism growth. Bacteriophages represent a rich and unique resource of anti-infectives to counter the growing world-wide problem of antibiotic resistance. In this study, we compared the host range of lytic bacteriophages and temperate phagesbelonging to various genera, namely Staphylococcus, E. coli and Salmonella, with a range of clinical isolates using two methods: the classical agar overlay method and a newly developed MIC method. MIC was only observed with isolates that were susceptible to phage infection, which correlated with the agar overlay assay, whereas no MIC was detected with isolates that were resistant to phage infection. The simple MIC method was useful in determining phage adsorption and host range, and detecting possible prophage contamination in phage preparations. Interestingly, this method was also applicable to strain differentiation through phage susceptibility testing using a 96-well, high throughput format that proved to be easy, cost-effective, fast and reliable.

Lysis-deficient phages as novel therapeutic agents for controlling bacterial infection
Vivek Paul, Sudarson Sundarrajan, Sanjeev Rajagopalan, Sukumar Hariharan, Nanjundappa Kempashanaiah, Sriram Padmanabhan, Bharathi Sriram, Janakiraman Ramachandran
BMC Microbiology , 2011, DOI: 10.1186/1471-2180-11-195
Abstract: We developed a recombinant lysis-deficient Staphylococcus aureus phage P954, in which the endolysin gene was rendered nonfunctional by insertional inactivation. P954, a temperate phage, was lysogenized in S. aureus strain RN4220. The native endolysin gene on the prophage was replaced with an endolysin gene disrupted by the chloramphenicol acetyl transferase (cat) gene through homologous recombination using a plasmid construct. Lysogens carrying the recombinant phage were detected by growth in presence of chloramphenicol. Induction of the recombinant prophage did not result in host cell lysis, and the phage progeny were released by cell lysis with glass beads. The recombinant phage retained the endolysin-deficient genotype and formed plaques only when endolysin was supplemented. The host range of the recombinant phage was the same as that of the parent phage. To test the in vivo efficacy of the recombinant endolysin-deficient phage, immunocompromised mice were challenged with pathogenic S. aureus at a dose that results in 80% mortality (LD80). Treatment with the endolysin-deficient phage rescued mice from the fatal S. aureus infection.A recombinant endolysin-deficient staphylococcal phage has been developed that is lethal to methicillin-resistant S. aureus without causing bacterial cell lysis. The phage was able to multiply in lytic mode utilizing a heterologous endolysin expressed from a plasmid in the propagation host. The recombinant phage effectively rescued mice from fatal S. aureus infection. To our knowledge this is the first report of a lysis-deficient staphylococcal phage.Bacteriophages are attractive as therapeutic agents because they are safe for humans and highly specific and lethal to the bacteria they target. Further, phages can be developed rapidly to combat the emergence of antibiotic-resistant pathogenic bacteria [1,2]. Phage therapy is currently practiced routinely and successfully in countries such as Poland and Russia [3]. The recent approval of c
Therapeutic Potential of Staphylococcal Bacteriophages for Nasal Decolonization of Staphylococcus aureus in Mice  [PDF]
Madhavi H. Narasimhaiah, Jiya Y. Asrani, Sundaram M. Palaniswamy, Jagadeesh Bhat, Shilpa E. George, Rajamuthu Srinivasan, Aradhana Vipra, Srividya N. Desai, Raghu Patil Junjappa, Panchali Roy, Bharathi Sriram, Sriram Padmanabhan
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.31008
Abstract:

Bacteriophages represent a rich and unique resource of anti-infectives to counter the global problem of antibiotic resis- tance. In this work, we assessed the bactericidal activity of two virulent staphylococcal phages, K and 44AHJD, against S. aureus isolates of clinical significance, and tested their efficacy in vivo. The phage cocktail lysed >85% of the clinical isolates tested. Both the phages were purified by ion-exchange column chromatography following propagation in bioreactors. The purity profiles of the ion-exchange purified phages were compared with those of phages purified using cesium chloride density gradient ultracentrifugation, and infectiousness of the purified phages was confirmed by plaque forming assay. The in vivo efficacy of a phage cocktail was evaluated in an experimental murine nasal colonization model, which showed that the phage cocktail was efficacious. To our knowledge, this is the first report of phage use in an in vivo model of nasal carriage.

Antibacterial and antifungal screening on various leaf extracts of Barringtonia acutangula
R. Vijaya bharathi, A. Jerad Suresh, M. Thirumal, S. Geetha Lakshmi, B. Kumudhaveni,Latha Sriram
International Journal of Research in Pharmaceutical Sciences , 2010,
Abstract: The various extracts of leaves of Barringtonia acutangula (Lecythidaceae) viz., n-hexane, chloroform, ethyl acetate and ethanol were subjected to preliminary phytochemical screening and screened for their antibacterial activity against gram-positive (Staphyloccocus aureus, Entero cocci, Coagulase staphylococci) and gram-negative bacteria (Escherichia coli, Klebsiella, Citrobacter, Aceneto bacter, Pseudomonas, Salmonella typhi and Salmonella paratyphi) using Minimum Inhibitory Concentration (MIC) and zone of inhibition by Agar Disc Diffusion method.. The results of the preliminary investigation revealed the presence of terpenoids, steroids, tannins, saponins, flavanoids and glycosides. Among the crude extracts, n-Hexane extract showed good antibacterial activity against all tested organisms followed by chloroform (MIC = 100 μg/ml), Ethyl acetate (MIC = 100 μg/ml), ethanol and aqueous extracts (MIC = 166.67 μg/ml). Results on the zone of inhibition (mm) revealed n-Hexane extract showed the maximum antibacterial potential followed by ethyl acetate, ethanol, aqueous and chloroform. The extracts were subjected to antifungal activity using MIC method against Candida albicans, Aspergillus flavus, Aspergillus fumigatus and Aspergillus niger. The n-Hexane extract inhibited growth of pathogenic fungi at a lesser concentration followed by aqueous, ethanol, chloroform and ethyl acetate. The results reveal that the Barringtonia acutangula leaves possess potential antibacterial and antifungal activity. Further study can be extrapolated towards the isolation of the active constituents.
A novel bacteriophage Tail-Associated Muralytic Enzyme (TAME) from Phage K and its development into a potent antistaphylococcal protein
Vivek Paul, Sanjeev Rajagopalan, Sudarson Sundarrajan, Shilpa E George, Jiya Y Asrani, Renjith Pillai, Ravisha Chikkamadaiah, Murali Durgaiah, Bharathi Sriram, Sriram Padmanabhan
BMC Microbiology , 2011, DOI: 10.1186/1471-2180-11-226
Abstract: We identified a phage K gene, designated orf56, as encoding the phage tail-associated muralytic enzyme (TAME). The gene product (ORF56) contains a C-terminal domain corresponding to cysteine, histidine-dependent amidohydrolase/peptidase (CHAP), which demonstrated muralytic activity on a staphylococcal cell wall substrate and was lethal to S. aureus cells. We constructed N-terminal truncated forms of ORF56 and arrived at a 16-kDa protein (Lys16) that retained antistaphylococcal activity. We then generated a chimeric gene construct encoding Lys16 and a staphylococcal cell wall-binding SH3b domain. This chimeric protein (P128) showed potent antistaphylococcal activity on global clinical isolates of S. aureus including methicillin-resistant strains. In addition, P128 was effective in decolonizing rat nares of S. aureus USA300 in an experimental model.We identified a phage K gene that encodes a protein associated with the phage tail structure. The muralytic activity of the phage K TAME was localized to the C-terminal CHAP domain. This potent antistaphylococcal TAME was combined with an efficient Staphylococcus-specific cell-wall targeting domain SH3b, resulting in the chimeric protein P128. This protein shows bactericidal activity against globally prevalent antibiotic resistant clinical isolates of S. aureus and against the genus Staphylococcus in general. In vivo, P128 was efficacious against methicillin-resistant S. aureus in a rat nasal colonization model.Peptidoglycan-degrading enzymes or murein hydrolases have the ability to digest bacterial cell walls. Such enzymes from bacteriophages represent a unique class of antibacterial agents because of their ability to cleave bacterial peptidoglycan in a species-specific or genus-specific manner. Thus, they provide a means to selectively target pathogens [1-3].At the end of the bacteriophage infection process, progeny are released from the host cell by lysis, which is mediated by two phage-encoded gene products, endolysins
Biochemical characterization and evaluation of cytotoxicity of antistaphylococcal chimeric protein P128
Shilpa E George, Ravisha Chikkamadaiah, Murali Durgaiah, Amruta A Joshi, Ullas P Thankappan, Shampur N Madhusudhana, Bharathi Sriram
BMC Research Notes , 2012, DOI: 10.1186/1756-0500-5-280
Abstract: We evaluated the requirement or effect of divalent cations and the metal ion chelator, EDTA upon biological activity of P128. As the protein is intended for therapeutic use, we tested its activity in presence of body fluids and antibodies specific to P128. For the same reason, we used standard human cell lines to evaluate cytotoxic effects, if any.The divalent cations, calcium and magnesium at upto 25?mM and Zinc upto 2.5?mM neither inhibited nor enhanced P128 activity. Incubation of this protein with EDTA, human serum, plasma and blood also did not alter the antibacterial properties of the molecule. No inhibitory effect was observed in presence of hyper-immune sera raised against the protein. Finally, P128 did not show any cytotoxic effect on HEp2 and Vero cells at the highest concentration (5?mg/mL) tested.The results presented here throw light on several properties of protein P128. Taken together, these substantiate the potential of P128 for therapeutic use against S. aureus. Further development of the protein and conduct of preclinical safety studies in animals is warranted.Current treatment for staphylococcal infections face multiple challenges including spread of highly virulent strains in the hospital and community environments. Novel therapeutic agents and modalities are becoming a necessity to combat the often invasive infections by these strains [1,2].In S. aureus and other Gram-positive bacteria, where the outer membrane is absent, the multilayered peptidoglycan or murein, commonly referred to as the cell wall, represents the limit of the cell. Peptidoglycan is an important component in these bacteria, conferring strength and rigidity to the cell, allowing growth and division, maintaining cell shape, and protecting against osmotic lysis [3]. The peptidoglycan therefore presents an excellent target for antimicrobial action. Murein degrading enzymes that are capable of hydrolyzing the various carbohydrate or protein linkages of the peptidoglycan layer bring
Antistaphylococcal activity of bacteriophage derived chimeric protein P128
Aradhana A Vipra, Srividya Desai, Panchali Roy, Raghu Patil, Juliet Raj, Nagalakshmi Narasimhaswamy, Vivek Daniel Paul, Ravisha Chikkamadaiah, Bharathi Sriram
BMC Microbiology , 2012, DOI: 10.1186/1471-2180-12-41
Abstract: Here we report results of in vitro studies evaluating the susceptibility of staphylococcal strains to this novel protein.Using the broth microdilution method adapted for lysostaphin, we found that P128 is effective against S. aureus clinical strains including MRSA, methicillin-sensitive S. aureus (MSSA), and a mupirocin-resistant S. aureus. Minimum bactericidal concentrations and minimum inhibitory concentrations of P128 (1-64 μg/mL) were similar across the 32 S. aureus strains tested, demonstrating its bactericidal nature.In time-kill assays, P128 reduced colony-forming units by 99.99% within 1 h and inhibited growth up to 24 h.In an assay simulating topical application of P128 to skin or other biological surfaces, P128 hydrogel was efficacious when layered on cells seeded on solid media. P128 hydrogel was lethal to Staphylococci recovered from nares of healthy people and treated without any processing or culturing steps, indicating its in situ efficacy. This methodology used for in vitro assessment of P128 as an agent for eradicating nasal carriage is unique.The novel chimeric protein P128 is a staphylococcal cell wall-degrading enzyme under development for clearance of S. aureus nasal colonization and MRSA infection. The protein is active against globally prevalent antibiotic-resistant clinical isolates and other clinically significant staphylococcal species including S. epidermidis. The P128 hydrogel formulation was bactericidal against Staphylococci including S. aureus recovered from the nares of 31 healthy people, demonstrating its in situ efficacy.Antibiotic-resistant Staphylococcus aureus strains emerging from the community as well as hospital environments represent a global threat [1,2], requiring new approaches to control this pathogen. The anterior nare is the major reservoir of S. aureus in humans; 80% of the human population may be carriers [3]. A causal relationship between nasal colonization of S. aureus and serious infection has been established; thu
A Bayesian Approach to Identify Photos Likely to Be More Popular in Social Media  [PDF]
Arunabha Choudhury, Sriram Nagaswamy
Journal of Computer and Communications (JCC) , 2015, DOI: 10.4236/jcc.2015.311031
Abstract:

With cameras becoming ubiquitous in Smartphones, it has become a very common trend to capture and share moments with friends and family in social media. Arguably, the 2 most relevant factors that contribute to the popularity are: the user’s social aspect and the content of the image (image quality, objects in the image etc.). In recent years, due to various security concerns, it has been increasingly difficult to derive social attributes from social media. Due to this limitation, in this paper we study what make images popular in social media based on the image content alone. We use Bayesian learning approach with variable likelihood function in order to predict image popularity. Our finding shows that a mapping between image content to image popularity can be achieved with a significant recall and precision. We then use our model to predict images that are likely to be more popular from a set of user images which eventually facilitate easy share.

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Bharathi M
Indian Journal of Medical Microbiology , 2003,
Abstract:
Authors′ reply
Scott Bharathi
Annals of Cardiac Anaesthesia , 2008,
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