Kiran Tiwari | Illinois State University (original) (raw)

Books by Kiran Tiwari

Papers by Kiran Tiwari

Our Nature, Jan 1, 2007

Bacillus thuringiensis strains were isolated from soil samples collected from Khumbu Base Camp of... more Bacillus thuringiensis strains were isolated from soil samples collected from Khumbu Base Camp of the Everest region and characterized by standard microbiological techniques viz. colonial and morphological characteristics, and biochemical tests. Insect bioassay of each isolate was performed by standard method using mosquito larva. Among ten randomly selected isolates, one isolate showed the highest insecticidal activity against Dipteron insects.

Nepal Journal of …, Jan 1, 2008

Streptomyces spp. (Lob18.2b), isolated from soil sample from Everest Base Camp, was obtained from... more Streptomyces spp. (Lob18.2b), isolated from soil sample from Everest Base Camp, was obtained from Research Laboratory for Biotechnology and Biochemistry (RLABB). The isolate was found to inhibit Salmonella paratyphi, Salmonella typhi, Proteus mirabilis, Proteus vulgaris, Shigella sonnei, Klebsiella pneumoniae, Klebsiella oxytoca, Escherichia coli, Bacillus subtilis and Staphylococcus aureus on primary screening. Secondary screening was done using fermented starch casein broth of the streptomycete to its stationary phase culture. The antibacterial agent was highly effective against all susceptible Gram negative bacteria except Proteus spp. Gram positive bacteria were relatively lesser sensitive. Pseudomonas aeruginosa was resistant to the agent. Antibacterial activity of aqueous fraction obtained from fermented broth of streptomycete culture was more effective than that of organic fraction of same extract. Thin layer chromatography revealed that the test compound was relatively nonpolar compared to the known antibiotics. Among the tested standard antibiotics, the chemical characteristic of the antibacterial agent was comparable to streptomycin.

Microbiology, Jan 1, 2012

The clpC operon in Staphylococcus aureus comprises four genes, denoted ctsR, mcsA, mcsB and clpC.... more The clpC operon in Staphylococcus aureus comprises four genes, denoted ctsR, mcsA, mcsB and clpC. A mutation within the mcsB gene resulted in hypersensitivity to heavy metal stress, temperature stress, osmotic pressure stress and oxidative stress. This mutation also resulted in sensitivity to variations in pH and lowered expression of the clpC operon under adverse extracellular conditions, as determined by quantitative real-time PCR (qRT-PCR). Additionally, virulence traits such as haemolytic activity, proteolysis, biofilm formation, and evasion from peritoneal fluid killing were substantially reduced in the DmcsB strain. Interestingly, mutated mcsB also caused a significant reduction in expression of virulence determinants hla and saeS. To be a successful pathogen, S. aureus must effectively overcome these types of stresses that are encountered within the host. These data show that an S. aureus strain lacking functional mcsB is stress hypersensitive and therefore less viable when introduced into hostile environments. For the first time, these studies have identified mcsB as a crucial and necessary component of stress and pathogenicity mechanisms.

International Journal of Life …, Jan 1, 2007

A study was conducted to elucidate the lactose assimilation by indigenious strains of yeasts in N... more A study was conducted to elucidate the lactose assimilation by indigenious strains of yeasts in Nepal. A total of 31 strains were isolated from eight murcha (yeast cakes) samples from different localities of Nepal. A higher percentage of isolates (7/31, 22.58%) were found to posses lactose assimilating activity. Among the lactose assimilating isolates 57.14% (4/7) were able to assimilate galactose, a product of ß-galactosidase reaction. Abundance of lactose assimilating yeasts from Nepalese Murcha (Yeast cake). Int J Life Sci 1 : 1-5

Mobile Genetic …, Jan 1, 2012

International Journal of …, Jan 1, 2010

Sodium azide was employed to generate mutants of actinomycetes from Mount Everest region, viz. Sa... more Sodium azide was employed to generate mutants of actinomycetes from Mount Everest region, viz. Sagarmatha National Park, Jorsale, Kalapatthar and Namche. Individual isolates of actinomycetes were inoculated on Starch Casein Agar plates containing 10, 50 and 100 ppm of sodium azide. Depending on complete inhibition of their growth , actinomycete isolates were categorized as highly sensitive , moderately sensitive and tolerant, respectively. Out of a total of 38 actinomycetes isolates, two (5.3%) were highly sensitive, 23 (60.5%) moderately sensitive and 13 (34.2%) tolerant. A total of 21 mutants were generated by treating 8 of the 23 moderately sensitive actinomycetes with 20, 30 and 40 ppm ( sublethal concentrations ) of sodium azide and analyzed morphologically and biochemically. All mutants like wild strains were able to hydrolyse starch, Tween 20 and casein and utilize fructose and lactose. All were urease and catalase positive , but were different from wild strains in colony color or texture or both. Altogether nine (43 % ) mutants having negative mutation in loci of utilization of galactose or mannose (loss-of-function LOF, single mutants ) , two LOF double mutants in utilization of both galactose and arabinose , one gain-of-function (GOF) single mutant having positive mutation in the loci of utilization of galactose, one GOF double mutant in utilization of mannose and galactose and five double mutants (25%) having GOF ( arabinose or sucrose ) as well as LOF ( mannose or galactose or arabinose) were obtained.

International Journal of Life Sciences, Jan 1, 2009

Staphylococcus aureus, one notable example of nosocomial infections, has the characteristic abili... more Staphylococcus aureus, one notable example of nosocomial infections, has the characteristic ability to acquire antimicrobial resistance. Methicillin-resistant S. aureus have already become endemic worldwide, and vancomycin is the terminal antibiotic of choice for treatment of infections by these strains. Because of selection of vancomycin as the treatment option, n ow, the emergence of vancomycin resistance in S. aureus has been increasing elsewhere. Further, there is no consensus definition of minimum inhibitory concentration to determine the levels of vancomycin resistance in these strains making it difficult in interpretation and management of the resistant strains. As an intervention against cell wall physiology of the bacteria, vancomycin binds with terminal dipeptide of the peptidoglycan monomer. However, vancomycin-resistant strains possess a thickened cell wall with many free monomers capable of binding with the drug. The thickened cell wall not only traps more vancomycin molecules on the immediate cell surface, but also significantly impedes action of the drug towards inner layers of the peptidoglycan network on bacteria. Thus, the normal inner layers of peptidoglycan ensure the structural integrity of cell as a whole. Compounding with the stress selection of vancomycin-resistance in S. aureus, the novel mechanism allows the bacteria to reduce susceptibility to the drug easily; hence, emergence of vancomycin resistant strains in the hospital environment may occur faster than expected.

International Journal of …, Jan 1, 2007

Glucose isomerase (EC 5.3.1.5) was extracted from Streptomyces spp., isolated from Mt. Everest so... more Glucose isomerase (EC 5.3.1.5) was extracted from Streptomyces spp., isolated from Mt. Everest soil sample, and purified by ammonium sulfate fractionation and Sepharose-4B chromatography. A 7.1 fold increase in specific activity of the purified enzyme over crude was observed. Using glucose as substrate, the Michaelis constant (K M ) and maximal velocity (V max ) were found to be 0.45M and 0.18U/mg. respectively. The optimum substrate (glucose) concentration, optimum enzyme concentration, optimum pH, optimum temperature, and optimum reaction time were 0.6M, 62.14μg/100μl, 6.9, 70ºC, and 30 minutes, respectively. Optimum concentrations of Mg 2+ and Co 2+ were 5mM and 0.5mM, respectively. The enzyme was thermostable with half-life 30 minutes at 100ºC. Dhungel B, Subedi M, Tiwari KB, Shrestha UT, Pokhrel S and Agrawal VP (2007)Thermostable glucose isomerase from psychrotolerant Streptomyces species. Int J Life Sci 1 : 6-10

Nepal Medical College …, Jan 1, 2007

This study was conducted at Tribhuvan University Teaching Hospital, a tertiary care hospital in N... more This study was conducted at Tribhuvan University Teaching Hospital, a tertiary care hospital in Nepal from January 2001 to March 2002. The prevalence of bacterial meningitis, its causative organisms and their antibiotic sensitivity patterns were studied in cerebrospinal fluid of 448 suspected cases. The prevalence of acute bacterial meningitis was 8.3%. There was no significant association (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05) of the disease with gender (X2 = 0.0234) and among different age groups (X2 = 6.07875) studied. The causative bacteria were Pseudomonas aeruginosa (24.3%), Klebsiella pneumoniae (16.2%), Staphylococcus aureus (16.2%), coagulase negative staphylococci (10.8%), Escherichia coli (10.8%), Streptococcus pneumoniae (8.2%), Neisseria meningitidis (5.4%), Acinetobacter spp. (5.4%) and Aeromoanas spp. (2.7%). Imipenem was the most effective antibiotic, however, 11.1% of P. aeruginosa, 25.0% of E. coli and 50.0% of Acinetobacter spp. were resistant to the drug.