Taghrid Istivan - Academia.edu (original) (raw)

Papers by Taghrid Istivan

Campylobacter concisus is an emerging pathogen that causes gastroenteritis and is a suspected cau... more Campylobacter concisus is an emerging pathogen that causes gastroenteritis and is a suspected cause of inflammatory bowel diseases. Its importance is enhanced by the chronic sequela that results from acute infection. This bacterium has been under-diagnosed in intestinal infectious diseases, and its clinical importance has not been determined yet. In order to establish the implication of this emerging bacterial species in human gastroenteritis and other infections, different approaches and procedure have been performed, where molecular typing methods have played a central role. The chapter provides a comprehensive past and recent updates on the detection of C. concisus by biochemical and molecular methods.

Royal Society open science, May 1, 2024

Campylobacter concisus is an opportunistic bacterial pathogen linked with a range of human diseas... more Campylobacter concisus is an opportunistic bacterial pathogen linked with a range of human diseases. The objective of this study was to investigate the viable but nonculturable (VBNC) state of the bacterium. To induce the VBNC state, C. concisus cells were maintained in sterilized phosphatebuffered saline at 4°C for three weeks. The VBNC cells were monitored using quantitative analysis by propidium monoazide (PMAxx) coupled with quantitative real-time PCR (PMAxx-qPCR), targeting the DNA gyrase subunit B gene. The results demonstrated that C. concisus ATCC 51562 entered VBNC state in 15 days, while ATCC 51561 entered the VBNC state in 9 days. The viable cell counts, assessed by PMAxx-qPCR, consistently remained close to the initial level of 10 7 CFU/ml, indicating a substantial portion of the cell population had entered VBNC state. Notably, morphological analysis revealed that the VBNC cells became coccoid and significantly smaller. The cells could be resuscitated through a temperature increase in the presence of a highly nutritious growth medium. In conclusion, under environmental stress, most C. concisus cells converted to VBNC state. The VBNC state of C. concisus may be important for its environmental survival and spread, and the presence of VBNC forms should be considered in environmental and clinical monitoring. This adaptation allows them to optimize resource utilization while preserving their structural and genetic integrity, ultimately enhancing their resilience and tolerance to adverse conditions. One crucial survival strategy observed in some bacteria is the

Microbiology, May 1, 2006

Phospholipase A (PLA) is one of the few enzymes present in the outer membrane of Gram-negative ba... more Phospholipase A (PLA) is one of the few enzymes present in the outer membrane of Gram-negative bacteria, and is likely to be involved in the membrane disruption processes that occur during host cell invasion. Both secreted and membrane-bound phospholipase A 2 activities have been described in bacteria, fungi and protozoa. Recently there have been increasing reports on the involvement of PLA in bacterial invasion and pathogenesis. This review highlights the latest findings on PLA as a virulence factor in Gram-negative bacteria.

Food Chemistry, Jul 1, 2022

This work examines the relationship between microstructural properties of hot-moulded chitosan ne... more This work examines the relationship between microstructural properties of hot-moulded chitosan networks, crosslinked with trisodium phosphate, and diffusive behaviour from these networks. Analysis through infrared spectroscopy (FTIR) confirmed successful crosslinking of the polymer chains and bioactive entrapment, while X-ray diffraction (WAXD) and dynamic oscillation in-shear elucidated the higher order structural properties of each matrix, as they transitioned from solutions to amorphous gels to semi-crystalline matrices. The picture of molecular motion observed in these systems and consequent application of the Flory-Rehner theory further indicated that different extents of chitosan crosslinking yielded a distinct water infusion functionality seen in the levels of swelling. Diffusion of caffeine from these delivery vehicles showed that network structural properties (governed by crosslinker concentration) had a significant effect on the release kinetics of the entrapped bioactive. The relationship between network mesh characteristics and diffusion properties were further confirmed by correlating caffeine release rates and molecular pore size.

IntechOpen eBooks, Apr 8, 2021

Open Journal of Medical Microbiology, 2014

We developed and evaluated a multiplex PCR (m-PCR) for application in routine diagnostic laborato... more We developed and evaluated a multiplex PCR (m-PCR) for application in routine diagnostic laboratories to detect Campylobacter spp. in stool samples including C. concisus, C. jejuni, and C. coli. When this m-PCR was applied on spiked faecal samples, C. concisus, C. jejuni, and C. coli were specifically identified at 10 5 cells/gm of faeces. To compare the sensitivity of the m-PCR with conventional culture techniques, the same spiked stool samples were cultured on an antibiotic free Columbia blood agar using the filtration technique. The detection limit of conventional culture method was 10 5 cells/gm of stool for C. concisus and 10 6 cells/gm of stool for C. jejuni and C. coli. The m-PCR was applied to test 127 faecal samples from children with gastroenteritis and the results were compared with the conventional bacterial cultures data. By this m-PCR technique, C. jejuni was detected in 7 samples, C. coli in 2 samples, and C. concisus in 7 samples. However, the conventional culture results for these samples were 6 for C. jejuni, 2 for C. coli and only one sample was positive for C. concisus. In total, 19 samples were positive for Campylobacter spp. by m-PCR while only 9 samples were positive for Campylobacter spp. by culture. In conclusion, m-PCR is more sensitive than the culture technique to detect C. concisus and other fastidious campylobacters in faeces.

Veterinary Microbiology, Mar 1, 2006

A novel outer membrane protein-encoding gene was identified in Brachyspira hyodysenteriae. The pr... more A novel outer membrane protein-encoding gene was identified in Brachyspira hyodysenteriae. The predicted protein, SmpB, was encoded by a gene that contains regions of identity with that encoding the previously identified lipoprotein SmpA. However, the majority of the reading frame encoding SmpA and SmpB share no detectable similarity. Analysis of several strains revealed that B. hyodysenteriae harbours either smpA or the newly identified gene smpB, but not both. smpB encodes for a slightly larger protein than smpA, 17.6 and 16.8 kDa, respectively. The predicted proteins share an identical leader sequence and the first 10 amino acids of the mature protein, however, the remainder of the predicted protein sequence shows no similarity. It is hypothesised that smpA and smpB are present on the same area of the chromosome. The proteins are antigenically unique, as antisera raised against a strain of B. hyodysenteriae that expresses SmpA cannot detect SmpB and vice versa. Although the presence of an identical leader peptide suggests identical localisation of SmpA and SmpB, it is not known if the two predicted proteins share similar function.

Microbiology Australia

Campylobacter concisus, a member of the human’s oral microflora, is a Gram-negative, fastidious, ... more Campylobacter concisus, a member of the human’s oral microflora, is a Gram-negative, fastidious, microaerophilic bacterium. However, it is debatable whether it should be recognised as a commensal of the human oral cavity, or an opportunistic pathogen as it has been linked to oral and gastrointestinal infections. But there is no doubt that its biofilm-forming capacity has enhanced its survival mechanism whether as a commensal or a pathogen. Hence, through our investigation to assess C. concisus biofilms, we believe that its survival strategy in the oral cavity is enhanced by being protected in the biofilm environment with other oral microbes. Our hypothesis is supported by the findings that oral isolates of this bacterium possess a significantly higher biofilm forming capability than those isolated from the gastrointestinal tract.

Food Chemistry, 2022

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With a large number of DNA and protein sequences already known, the crucial question is to find o... more With a large number of DNA and protein sequences already known, the crucial question is to find out how the biological function of these bio-molecules is "written" in the sequence of nucleotides or amino acids. Biological processes in any living organism are based on selective interactions between particular bio-molecules, mostly proteins. However, the rules governing the coding of the protein's biological function, i.e. its ability to selectively interact with other molecules, are still not elucidated. With the rapid accumulation of databases for protein primary structures, there is an urgent need for theoretical approaches that are capable of analysing protein structure-function relationships. The Resonant Recognition Model (RRM) (1) is one attempt to identify the selectivity of protein interactions within an amino acid sequence. The RRM approach (2,3) proposes that protein interactions are electromagnetic in nature and their selectivity is based on resonant energy ...

Campylobacter [Working Title], 2021

With a large number of DNA and protein sequences already known, the crucial question is to find o... more With a large number of DNA and protein sequences already known, the crucial question is to find out how the biological function of these bio-molecules is “written” in the sequence of nucleotides or amino acids. Biological processes in any living organism are based on selective interactions between particular bio-molecules, mostly proteins. However, the rules governing the coding of the protein’s biological function, i.e. its ability to selectively interact with other molecules, are still not elucidated. With the rapid accumulation of databases for protein primary structures, there is an urgent need for theoretical approaches that are capable of analysing protein structure-function relationships. The Resonant Recognition Model (RRM) (1) is one attempt to identify the selectivity of protein interactions within an amino acid sequence. The RRM approach (2,3) proposes that protein interactions are electromagnetic in nature and their selectivity is based on resonant energy transfer betwee...

Campylobacter concisus is a human oral cavity bacterium, which has been linked to oral cavity inf... more Campylobacter concisus is a human oral cavity bacterium, which has been linked to oral cavity infections such as gingivitis and periodontitis for the last twenty years. C. concisus has also been isolated from non-oral sources since 1989 and was considered

With a large number of DNA and protein sequences already known, the crucial question is to find o... more With a large number of DNA and protein sequences already known, the crucial question is to find out how the biological function of these bio-molecules is “written” in the sequence of nucleotides or amino acids. Biological processes in any living organism are based on selective interactions between particular bio-molecules, mostly proteins. However, the rules governing the coding of the protein’s biological function, i.e. its ability to selectively interact with other molecules, are still not elucidated. With the rapid accumulation of databases for protein primary structures, there is an urgent need for theoretical approaches that are capable of analysing protein structure-function relationships. The Resonant Recognition Model (RRM) (1) is one attempt to identify the selectivity of protein interactions within an amino acid sequence. The RRM approach (2,3) proposes that protein interactions are electromagnetic in nature and their selectivity is based on resonant energy transfer betwee...

Cancer Studies and Therapeutics, 2018

It has been proven that many of biological processes are frequency selective pro- cesses that rel... more It has been proven that many of biological processes are frequency selective pro- cesses that relate to quantum energy state of photosensitive molecules. It was shown that light- activated changes in protein energy states can induce or modulate biological processes. Various up-to-date methodologies that incorporate low-intensity light into therapeutic procedures have been integrated into modern medicine. Here we have studied experimentally the hypothesis of the Resonant Recognition Model (RRM) that selectivity of protein activities is based on speci¯c resonant electromagnetic interactions [1]. The RRM theory proposes that an external electro- magnetic ¯eld at a particular activation frequency would produce resonant e®ects on protein biological activity, and this activation frequency can be determined computationally [1].

2012 International Conference on Biomedical Engineering (ICoBE), 2012

3C-SiC is currently under intense study as a potential material for implantable low power blood p... more 3C-SiC is currently under intense study as a potential material for implantable low power blood pressure sensing due to its biocompatibility. In this work, we present and discuss the fabrication processes for n-type 3C-SiC membranes using epitaxial SiC layers with thicknesses of 0.285 and 0.95 µm on Si substrates (650 µm). Membranes of n-type SiC with dimensions of 0.5×0.5 cm2

Future Medicinal Chemistry, 2012

Background: Resonant recognition model-myxoma virus (RRM-MV), a bioactive peptide analogue for my... more Background: Resonant recognition model-myxoma virus (RRM-MV), a bioactive peptide analogue for myxoma virus MV-T5 protein, was computationally designed by the RRM. In this study, the anticancer effects of RRM-MV were assessed in vitro against four negative control peptides on human skin cancer and normal cells. Results & discussion: The effects of RRM-MV versus negative control peptides on cells were evaluated by quantitative and qualitative assays. The RRM-MV treatment was able to induce cell death in cancer cells without triggering similar effects on normal cells. However, the negative control peptides produced no toxic effects on skin cancer and normal cells. No effects on human erythrocytes were detected when treated with all peptides. Conclusion: It is suggested that the RRM can be applied to design therapeutic anticancer peptides.

... An investigation on the composition of the subgingival microbiota in children with primary de... more ... An investigation on the composition of the subgingival microbiota in children with primary dentition aged 4-5 years ... Faecal material or other samples can be cultured by preparing a 1:2 to 1:10 suspensions in phosphate buffered saline (pH 7.4) or in heart infusion broth. ...

Royal Society open science, May 1, 2024

Microbiology, May 1, 2006

Food Chemistry, Jul 1, 2022

IntechOpen eBooks, Apr 8, 2021

Open Journal of Medical Microbiology, 2014

Veterinary Microbiology, Mar 1, 2006

Microbiology Australia

Food Chemistry, 2022

Campylobacter [Working Title], 2021

With a large number of DNA and protein sequences already known, the crucial question is to find o... more With a large number of DNA and protein sequences already known, the crucial question is to find out how the biological function of these bio-molecules is “written” in the sequence of nucleotides or amino acids. Biological processes in any living organism are based on selective interactions between particular bio-molecules, mostly proteins. However, the rules governing the coding of the protein’s biological function, i.e. its ability to selectively interact with other molecules, are still not elucidated. With the rapid accumulation of databases for protein primary structures, there is an urgent need for theoretical approaches that are capable of analysing protein structure-function relationships. The Resonant Recognition Model (RRM) (1) is one attempt to identify the selectivity of protein interactions within an amino acid sequence. The RRM approach (2,3) proposes that protein interactions are electromagnetic in nature and their selectivity is based on resonant energy transfer betwee...

Cancer Studies and Therapeutics, 2018

2012 International Conference on Biomedical Engineering (ICoBE), 2012

Future Medicinal Chemistry, 2012