RESEARCH ASSOCIATE, NATIONAL INSTITUTE OF IMMUNOLOGY, NEW DELHI, INDIA
WE ARE DEVELOPING BACTERIAL DNA AND MEMBRANE TARGETTING AGENTS TO ELIMINATE BIOFILM BACTERIA
Drug-resistance is a serious health care problem. The mortality rate is increasing exponentially in the world by these drug-resistant super bugs. Methicillin-resistant Staphylococcus aureus (MRSA) is one such organism which causes nosocomial (hospital-acquired) infections through biofilm formation. Biofilm is group of bacteria stuck together and it is very difficult to eradicate with common antibiotics and in some cases tremendously higher concentration of antibiotics are used to eradicate these films. These biofilms mainly cause bone infections and propagate inside the bone finally damages completely. We are developing agents which can eliminate this biofilm by diffusing inside the biofilm matrix and kill the underlying cells. Generally the biofilm matrix composed of extracellular DNA (eDNA) as a backbone on which bacterial cells are attached, then some other components like proteins and carbohydrates are also stuck to these structures. The amphiphilic molecule developed by us can chew this eDNA and attack the underlying bacteria, so that complete elimination of biofilm can be achieved. Further to deliver this agent in the environment specific manner we have used human serum albumin based nano-carrier (HNC) since HNC can degrade in the acidic environment. The release in the acidic environment is beneficial since biofilm inside environment is highly acidic, so that the release at normal pH will be minimal and this will not kill the normal mammalian cells. In addition the biofilm matrix is rich in proteases which enable higher release of the amphiphilc molecule only inside the biofilm matrix. This nanomaterial found to clear established MRSA biofilm by dual attack on eDNA and underlying bacterial cells. Finally this nano material was used to eradicate catheter-associated MRSA biofilm. The nano material was found to be non-toxic to the human embryonic kidney (HEK 293) cell lines. The non-toxic environment specific activity of this nano material could be a potential anti-biofilm agent against MRSA biofilms.
Abstract: A rationally designed bactericidal amphiphile acts on compelling targets and has the potential to disarm resistance development in pathogenic bacteria.
Pub.: 31 May '14, Pinned: 04 Oct '17
Abstract: Annihilation of bacterial biofilms is challenging owing to their formidable resistance to therapeutic antibiotics and thus there is a constant demand for development of potent antibiofilm agents that can abolish established biofilms. In the present study, the activity of a dipyridinium-based cationic amphiphile (compound 1) against established bacterial biofilms and the subsequent development of a compound 1-loaded nanocarrier for potential antibiofilm therapy are highlighted. Solution-based assays and microscopic analysis revealed the antagonistic effect of compound 1 on biofilms formed by Staphylococcus aureus MTCC 96 and Pseudomonas aeruginosa MTCC 2488. In combination studies, compound 1 could efficiently potentiate the action of tobramycin and gentamicin on P. aeruginosa and S. aureus biofilm, respectively. A human serum albumin (HSA)-based nanocarrier loaded with compound 1 was generated, which exhibited sustained release of compound 1 at physiological pH. The compound 1-loaded HSA nanocarrier (C1-HNC) displayed the signature membrane-directed activity of the amphiphile on target bacteria, efficiently eliminated established bacterial biofilms, and was observed to be nontoxic to a model human cell line. Interestingly, compound 1 as well as the amphiphile-loaded HSA nanocarrier could eradicate established S. aureus biofilm from the surface of a Foley's urinary catheter. On the basis of its biocompatibility and high antibiofilm activity, it is conceived that the amphiphile-loaded nanocarrier may hold potential in antibiofilm therapy.
Pub.: 28 Aug '14, Pinned: 04 Oct '17
Abstract: A pyridinium amphiphile-loaded Poly(lactic-co-glycolic acid) (PLGA) nanocarrier (C1-PNC) was developed as an adjuvant in order to break the resistance and restore susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) cells to therapeutic antibiotics. Notably, against a clinical MRSA strain, C1-PNC could render 8 × and 6 × reduction of the minimum biofilm eradication concentration (MBEC90) of gentamicin and ciprofloxacin, respectively. Mechanistic studies on MRSA planktonic cells revealed that in case of gentamicin, C1-PNC promoted enhanced cellular uptake of the antibiotic, while the propensity of C1-PNC to inhibit efflux pump activity could be leveraged to enhance cellular accumulation of ciprofloxacin leading to effective killing of MRSA cells. Interestingly, the combinatorial dosing regimen of C1-PNC and the antibiotics was non-toxic to cultured HEK 293 cells. It is conceived that the non-toxic amphiphile-loaded nanomaterial holds considerable prospect as an adjuvant for antibiotic-mediated alleviation of MRSA biofilm.
Pub.: 16 Jun '17, Pinned: 04 Oct '17
Abstract: Neutrophil extracellular traps (NETs) can be found at the sites of vascular lesions and in the circulation of patients with active small vessel vasculitis. Neutrophils from vasculitis patients release more NETs in vitro, and NETs have properties that can harm the vasculature both directly and indirectly. There are several ways to interfere with NET formation, which open for new therapeutic options. However, there are several types of NETs and different mechanisms of NET formation, and these might have different effects on inflammation. Here we review recent findings regarding the pathogenesis and therapeutic potentials of NETs in vasculitis.Experimental mouse models support a role for NETs in promoting vascular damage, where histones and mitochondrial DNA appear to be driving forces. Impaired formation of NETs, however, in an SLE-like mouse model leads to more severe disease, suggesting that NETs can be important in limiting inflammation. Studies on drug-induced vasculitis reveal that levamisole can induce NETosis via muscarinic receptors, predisposing for the generation of autoantibodies, including antineutrophil cytoplasmic autoantibodies (ANCA). This supports the notion that NETs can bridge the innate and adaptive immune systems.NETs can participate in the pathogenesis of vasculitis, but in some models there also seem to be protective effects of NETs. This complexity needs further evaluation with experimental models that are as specific as possible for human primary vasculitis.
Pub.: 29 Sep '17, Pinned: 04 Oct '17
Abstract: Biofilm is prevalent in various ecological niches, in which microbial cells interconnect with each other through extracellular polymeric substances including polysaccharides, extracellular DNA, and proteins. When living in biofilms, the microbial cells employ small signalling chemicals as their "language" to communicate mutually, and exhibit remarkable differences in physiology compared to those living in planktonic state. It has been proven that the development of biofilm is subject to the regulation of c-di-GMP, an important second messenger found in prokaryotes. Given its important roles of biofilms in microbial infection, industry application, plant-microbe interactions and environmental pollustion, biofilm is one of frontier research areas in microbiology. This special issue of "Biofilm and c-di-GMP" systematically reviews the current progresses in the multiple research frontiers, including biotechnology, infectious diseases, environmental microbiology and plant pathology, with special focus on the methods and techniques in biofilm research. We hope that the issue will boost the interest of students and young scientists in this exciting area of microbiology.
Pub.: 29 Sep '17, Pinned: 04 Oct '17