Sanjai Saxena

Anti-staphylococcal potential of Callistemon rigidus

The last decade witnessed the emergence of Staphylococcus aureus- a versatile human pathogen, as a deadly superbug. The enormous genetic plasticity of the organism assists it to endlessly evolve resistance mechanisms against existing anti-infectives thus necessitating the need to control the spread of resistant staphylococcal isolates in hospitals and health care settings. This in turn demands the incessant exploration of newer biological matrices in search of diverse chemical entities with novel drug targets. Since time immemorial higher plants continue to be the best source of newer compounds with high therapeutic potential. Lead fractions from same or different plants can be developed into effective antibacterial polyherbal formulations. A lead fraction from methanolic extract of leaves of Callistemon rigidus exhibited a dose dependent antistaphylococcal activity during in vitro agar well assay against a panel of twenty seven clinical multidrug resistant S. aureus isolates. Further, minimal inhibitory concentration (MIC) evaluation by in vitro 96-well microplate based assay established a MIC range of 1.25–80 μg/ml as compared to 5–320 μg/ml of positive control, Cefuroxime sodium. The MIC50 and MIC90 of the methanolic lead fraction were 5 μg/ml and 40 μg/ml respectively. The present study thus signifies the vast potential of the lead fraction from Callistemon rigidus for future development into a herbal drug/ formulation and to impede global health crisis due to multidrug resistant Staphylococcus aureus.

Antimicrobial Potential of Callistemon rigidus.

Abstract In vitro. investigation of the antimicrobial activity of a crude methanol extract of leaves of Callistemon rigidus. R.Br. (Myrtaceae) revealed potential antibacterial activity against a broad spectrum of multidrug-resistant human pathogens. Agar well diffusion assays of the test extract established significant concentration-dependent antibacterial activity against methicillin-resistant Staphylococcus aureus., vancomycin-intermediate Staphylococcus aureus., vancomycin-resistant Escherichia coli., extended spectrum β.-lactamase-producing E. coli., and multidrug-resistant Pseudomonas. spp.

Muscodor kashayum sp. nov. – a new volatile anti-microbial producing endophytic fungus

Muscodor kashayum (MycoBank no.: MB 803800; GenBank no.: KC481680) is a newly described endophytic fungus of a medicinal plant Aegle marmelos (Bael tree), growing in the tropical conserved rainforest in the Western Ghats of India. Muscodor kashayum possesses distinct morphological, molecular and physiological features from the earlier reported Muscodor species. The fungus forms characteristic rings of the ropy mycelium on potato dextrose agar medium. This sterile fungus is characterised by the presence of a pungent smell which is attributable to a blend of more than 23 volatile organic constituents, predominantly 3-cyclohexen-1-ol,1-(1,5-dimethyl-4-hexenyl)-4-methyl; 1,6-dioxacyclododecane-7,12-dione; 2,6-bis(1,1-dimethylethyl)-4-(1-oxopropyl) phenol; 2,4-di-tert-butylthiophenol and 4-octadecylmorpholine. In the in vitro anti-microbial assay using M. kashayum, growth of 75% of test fungi/yeasts and 72% of the test bacteria were completely inhibited. Therefore, M. Kashayum holds potential for future application to be used as a myco-fumigation agent.

Surmounting antimicrobial resistance in the Millennium Superbug: Staphylococcus aureus

Staphylococcus aureus is the third most dreaded pathogen posing a severe threat due to its refractory behavior against the current armamentarium of antimicrobial drugs. This is attributed to the evolution of an array of resistance mechanisms responsible for morbidity and mortality globally. Local and international travel has resulted in the movement of drug resistant S. aureus clones from hospitals into communities and further into different geographical areas where they have been responsible for epidemic outbreaks. Thus, there is a dire necessity to refrain further cross movement of these multidrug resistant clones across the globe. The plausible alternative to prevent this situation is by thorough implementation of regulatory aspects of sanitation, formulary usage and development of new therapeutic interventions. Various strategies like exploring novel antibacterial targets, high throughput screening of microbes, combinatorial and synthetic chemistry, combinatorial biosynthesis and vaccine development are being extensively sought to overcome multidrug resistant chronic Staphylococcal infections. The majority of the antibacterial drugs are of microbial origin and are prone to being resisted. Anti-staphylococcal plant natural products that may provide a new alternative to overcome the refractory S.aureus under clinical settings have grossly been unnoticed. The present communication highlights the new chemical entities and therapeutic modalities that are entering the pharmaceutical market or are in the late stages of clinical evaluation to overcome multidrug resistant Staphylococcal infections. The review also explores the possibility of immunity and enzyme-based interventions as new therapeutic modalities and highlights the regulatory concerns on the prescription, usage and formulary development in the developed and developing world to keep the new chemical entities and therapeutic modalities viable to overcome antimicrobial resistance in S. aureus.

Superoxide dismutase, protease and lipase expression in clinical isolates of Staphylococcus aureus: a tool for antimicrobial drug discovery

The rising incidents of invasive infections due to multidrug resistant Staphylococcus aureus necessitate the exploration of newer targets for development of antibiotics. Pathogenicity of S. aureus is attributed to a wide range of virulence factors. The aim of this study was to screen the production of three virulence factors viz. extracellular protease, extracellular lipase and superoxide dismutase in human pathogenic strains of S. aureus for development of a test panel which could aid in screening of natural products of plant and microbial origin. 27 clinical isolates were compared for their enzyme expression profiles of which eight were finally selected. Sau G5 was the only protease producing organism selected in the test panel, while Sau G3 and Sau G9 were best SOD producers and Sau G16, Sau G18, Sau G22, Sau A5 and Sau A2 exhibited highest expression among different groups of clinical staphylococci.

Evaluation of Alternaria alternata ITCC4896 for use as mycoherbicide to control Parthenium hysterophorus

Mycoherbicides are specialty biotechnology products which employ the use of fungi or fungal metabolites as non-chemical alternatives, thereby reducing the input of harmful chemicals to control noxious weeds. The present communication emphasises the potential of an indigenous isolate of Alternaria alternata ITCC 4896 as a mycoherbicide for the global weed Parthenium hysterophorus. Of the various spore concentrations tested by in vitro detached leaf bioassay, 1 × 106 spores/ml was the most effective, inducing 89.2% leaf area damage on the seventh day and was further tested by the whole plant bioassay. Both in vitro detached leaf assay and whole plant bioassay exhibited a similar trend in disease development, exhibiting 50% damage at 96 hours post-treatment. However, 100% mortality was observed in the whole plant bioassay on the seventh day. This is the very first report on the bioweedicidal potential of Alternaria alternata ITCC 4896 (LC#508) for use as a mycoherbicide for Parthenium hysterophorus.

Microbial Enzymes and Their Industrial Applications

Enzymes are biological catalysts produced in living cells. They are proteinaceous in nature, the exception being catalytic RNA, which are also referred to as ribozymes. The term ‘en zyme’ is derived from the Greek, meaning ‘in sour dough’. E. Buchner (1897) experimentally proved that cell-free extract from yeast could produce alcohol from sugars, and he referred to it as “zymase”. The unique characteristics that enzymes possess are that they (1) increase the rate of reaction they catalyze, without being consumed or lost; (2) act specifically with the substrate to produce the products; and (3) remain regulated from a state of low activity to high activity and vice versa. Enzymes have been grouped into six classes based on the types of reactions they catalyze (Table 9.1). All cellular processes are controlled by a coordinated sequence of reactions that have specifically been catalyzed by a defined set of enzymes.

Strategies of Strain Improvement of Industrial Microbes

Microbes produce a variety of products in very low concentrations which have been used as antibiotics, drugs, vitamins, enzymes, bulk organic compounds, polymers, amino acids, biofuels, etc. Prerequisite for efficient biotechnological processes at industrial scale requires the use of microbial strains which produce high titre of the desired product. However, this is not an inherent property of the selected microorganism(s); hence, modifications in their genetic material could possibly help in overcoming this limitation. Thus, industrially relevant microbes are subjected to a variety of treatments using physical, chemical or genetic tools to overproduce the desired metabolite and make the process cost efficient. This process of enhancing the biosynthetic capabilities of microbes to produce desired product in higher quantities is defined as microbial strain improvement.

Microbes in Production of Fine Chemicals (Antibiotics, Drugs, Vitamins, and Amino Acids)

Fine chemicals are single pure substances that are produced in small to medium quantities and have a high value (>US

Screening and Toxicity Analysis of Catechin Isomers Against FemA Protein.

10/kg). They are synthesized via multi-step batch chemical or biotechnological processes. Fine chemicals consist of organic aromatic compounds, organic amines, proteogenic/non-proteogenic amino acids, carbohydrates, heteroaromatic compounds, and saturated and unsaturated fatty acids, uses for which are found in the pharmaceutical, specialty chemical, agricultural, and cosmeceutical industries (Pollack 2007) (Fig. 8.1).