Browsing by Author "Khan, Asad U."

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Draft genome sequence of the first NDM-4-producing Escherichia coli strain (AK1), isolated from sewage water of a North Indian hospital
(American Society for Microbiology, 2017) Khan, Asad U.; Beg, Ayesha Z.; Verma, Praveen K.
We report here the draft genome sequence of the first isolated NDM-4-producing Escherichia coli strain, isolated from sewage water at a North Indian hospital. The genome has an assembly size of 5,076,053 bp, arranged in 129 contigs, with 5,271 genes and a G+C content of 50.47%.
Efficacy of E. officinalis on the cariogenic properties of Streptococcus mutans: a novel and alternative approach to suppress quorum-sensing mechanism
(Public Library of Science, 2012) Hasan, Sadaf; Danishuddin, Mohd; Adil, Mohd; Singh, Kunal; Verma, Praveen K.; Khan, Asad U.
The present study was focused on evaluating the potential of Emblica officinalis against cariogenic properties of Streptococcus mutans, a causative microorganism for caries. The effect of crude extract and ethanolic fraction from Emblica officinalis fruit was analysed against S. mutans. The sub-MIC concentrations of crude and ethanolic fraction of E. officinalis were evaluated for its cariogenic properties such as acid production, biofilm formation, cell-surface hydrophobicity, glucan production, sucrose-dependent and independent adherence. Its effect on biofilm architecture was also investigated with the help of confocal and scanning electron microscopy (SEM). Moreover, expression of genes involved in biofilm formation was also studied by quantitative RT- PCR. This study showed 50% reduction in adherence at concentrations 156 µg/ and 312.5 µg/ml of crude extract and ethanolic fraction respectively. However, the biofilm was reduced to 50% in the presence of crude extract (39.04 µg/ml) and ethanolic fraction (78.08 µg/ml). Furthermore, effective reduction was observed in the glucan synthesis and cell surface hydrophobicity. The qRT-PCR revealed significant suppression of the genes involved in its virulence. Confocal and scanning electron microscopy clearly depicted the obliteration of biofilm structure with reference to control. Hence, this study reveals the potential of E. officinalis fruit extracts as an alternative and complementary medicine for dental caries by inhibiting the virulence factors of Streptococcus mutans.
Eugenol-induced suppression of biofilm-forming genes in Streptococcus mutans: An approach to inhibit biofilms
(Elsevier B.V., 2014) Adil, Mohd; Singh, Kunal; Verma, Praveen K.; Khan, Asad U.
Streptococcus mutans is well documented as a major aetiological agent of dental caries. The ability to form a biofilm on tooth surfaces is the major virulence factor of this bacterium. The objective of this study was to evaluate the effect of eugenol on suppression of biofilm- and quorum sensing (QS)-related genes of S. mutans and to determine its putative mode of action. Eugenol was evaluated for its inhibitory activity against virulence properties such as adherence and biofilm formation. Morphological changes in the architecture of S. mutans and in the biofilm were analysed and observed using confocal laser scanning microscopy and transmission electron microscopy. The effects of eugenol on expression of biofilm- and QS-related genes (gtfB, gtfC, comDE, smu630, vicR, brpA, ftf, relA, gbpB and spaP) were checked by quantitative real-time PCR (qRT-PCR). The present data revealed that eugenol at a sub-minimum inhibitory concentration (sub-MIC) significantly downregulated the expression of tested genes but did not affect bacterial growth. These results suggest that a sub-MIC of eugenol can effectively suppress virulence genes. Thus, the results indicated that eugenol can inhibit caries-associated biofilm and showed its therapeutic potential against oral biofilm.
In vitro and in vivo inhibition of Streptococcus mutans biofilm by Trachyspermum ammi seeds: an approach of alternative medicine
(Elsevier, 2012) Khan, Rosina; Adil, Mohd; Danishuddin, Mohd; Verma, Praveen K.; Khan, Asad U.
The aim of this study was to evaluate the influence of the crude and active solvent fraction of Trachyspermum ammi on S. mutans cariogenicity, effect on expression of genes involved in biofilm formation and caries development in rats. GC-MS was carried out to identify the major components present in the crude and the active fraction of T. ammi. The crude extract and the solvent fraction exhibiting least MIC were selected for further experiments. Scanning electron microscopy was carried out to observe the effect of the extracts on S. mutans biofilm. Comparative gene expression analysis was carried out for nine selected genes. 2-Isopropyl-5-methyl-phenol was found as major compound in crude and the active fraction. Binding site of this compound within the proteins involved in biofilm formation, was mapped with the help of docking studies. Real-time RT-PCR analyses revealed significant suppression of the genes involved in biofilm formation. All the test groups showed reduction in caries (smooth surface as well as sulcal surface caries) in rats. Moreover, it also provides new insight to understand the mechanism influencing biofilm formation in S. mutans. Furthermore, the data suggest the putative cariostatic properties of T. Ammi and hence can be used as an alternative medicine to prevent caries infection.
Inhibition of major virulence pathways of Streptococcus mutans by Quercitrin and Deoxynojirimycin: a synergistic approach of infection control
(PLOS, 2014) Hasan, Sadaf; Singh, Kunal; Danisuddin, Mohd; Verma, Praveen K.; Khan, Asad U.
OBJECTIVES: To evaluate the synergistic effect of Quercitrin and Deoxynojirimycin (DNJ) together with their individual inhibitory effect against virulence pathways of Streptococcus mutans. METHODOLOGY: MICs of both the compounds were determined by the microdilution method, followed by their in vitrosynergy using checkerboard and time kill assay. The nature of interaction was classified as synergistic on the basis of fractional inhibitory concentration index (FICI) value of ≤0.5. Furthermore, the activity of Quercitrin and DNJ was evaluated individually and in combination against various cariogenic properties of S. mutans UA159 such as acidogenesis, aciduracity, glucan production, hydrophobicity, biofilm and adherence. Moreover, expression of virulent genes in S. mutans was analysed by quantitative RT- PCR (qRT-PCR) and inhibition of F1F0-ATPase, lactate dehydrogenase and enolase was also evaluated. Finally, scanning electron microscopy (SEM) was used to investigate structural obliteration of biofilm. RESULTS: The in vitro synergism between Quercitrin and DNJ was observed, with a FICI of 0.313. Their MIC values were found to be 64 μg/ml and 16 μg/ml respectively. The synergistic combination consistently showed best activity against all the virulence factors as compared to Quercitrin and DNJ individually. A reduction in glucan synthesis and biofilm formation was observed at different phases of growth. The qRT-PCR revealed significant downregulation of various virulent genes. Electron micrographs depicted the obliteration of biofilm as compared to control and the activity of cariogenic enzymes was also inhibited. CONCLUSIONS: The whole study reflects a prospective role of Quercitrin and DNJ in combination as a potent anticariogenic agent against S. mutans.