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Janez Škarja, 2016, magistrsko delo

Opis: In a developed world, water is used in a variety of installations and devices for the improvement of life standard. It is important for these elements to be suitably managed and maintained, otherwise they can present a risk to people's health. Although potable water from a public plumbing system coming via the water supply into an internal plumbing system normally is compliant with the regulations, the quality of water in an internal plumbing system often changes – water gets contaminated. There are several types of microorganisms that can grow in water. They carry a great potential for the growth and proliferation of bacteria from the genus Legionella that cause Legionnaires' disease and Pontiac Fever. Even the fact that Legionella infection has for several years been mentioned in the accident insurance conditions of insurance companies in relation to receiving the insurance fee as compensation for bed day, shows the extent and foremost the seriousness of the disease (5–15% mortality rate). The research part of the master thesis focused mainly on determining the presence of bacteria from the genus Legionella in the water of internal plumbing systems of healthcare facilities. During the entire research period of 8 years, 2,676 samples of cold and hot water were acquired from 23 healthcare facilities. The main purpose of the research was to determine the efficiency or adequacy of applied approaches, i.e. physical disinfection with heat and chemical disinfection with chlorine, in eliminating or reducing the amount of Legionella present in the water of selected healthcare facilities. Another aim was to evaluate the impact of softening potable water with polyphosphates on the proliferation of certain microorganisms in water, and to determine the by-products of chemical disinfection. Upon sampling, an organoleptic examination of water (appearance, odour), electrometric measurements of water temperature, and colorimetric measurements of free chlorine concentrations in water were performed. The data for the analysis of Legionella presence were acquired by water sampling and the isolation of bacteria found in the water. In order to acquire laboratory results of specific physical and chemical parameters, ion chromatography, gas chromatography, spectrophotometry, titration, and inductively coupled plasma – mass detector were used. Although water samples from only two healthcare facilities showed no presence of Legionella, the number of water samples with the presence of Legionella decreased for at least 25% from the beginning to the end of period set. Also, after certain general sanitary and technical measures a noticeable improvement within healthcare facilities after 2008 could be observed. Regarding the initial part of the set period, a more favourable relationship between positive and negative samples, a lower number of samples with highest concentrations of present Legionella, and a higher number of samples with lower concentrations of present Legionella were determined. The research has shown that the existing system of ensuring health-compliant water is fairly efficient; however, the results could be improved additionally by investing more into the preparation and renovation of systems. Due to a limited number of samples, a direct impact of adding polyphosphates to potable water could not be linked to the occurrence of Legionella. None of the samples showed an increased concentration of by-products of potable water disinfection. In its conclusion, the research has shown that the procedures after overheating and after chlorine disinfection result in a similar success. While filtration proved to be most efficient, from the perspective of Legionella infections the use of medical bathtubs can present a high risk to people's health, therefore such devices should be subject to more frequent maintenance and supervision.
Najdeno v: ključnih besedah
Povzetek najdenega: ...potable water, internal plumbing system, biofilm, health facilities, disinfection, Legionella...
Ključne besede: potable water, internal plumbing system, biofilm, health facilities, disinfection, Legionella
Objavljeno: 05.09.2016; Ogledov: 3099; Prenosov: 189
.pdf Polno besedilo (1,70 MB)

Barbara Debeljak, 2018, doktorska disertacija

Opis: The hyporheic zone has been recognised as a functionally important component of streams and rivers. Due to increasing human impact on ecosystems, studies that assess ecological responses of the hyporheic zone are of great importance. The objectives of the thesis are to study the responses of abiotic parameters, sediment biofilm characteristics (the in situ respiration (R), potential respiratory activity (ETSA), protein content), and invertebrate assemblages (analysed as total assemblages, EPT assemblages and Copepoda assemblages) in the hyporheic zones related to different land use patterns (forest, agricultural and urban areas). The focus of study also includes the impact of clogging. This research is comprised of three sampling campaigns conducted in summer (2013), winter (2013) and spring (2014) in five pre-Alpine Slovenian rivers. For each river, three or six sampling locations were chosen in the downwelling hyporheic sections of three dominant land uses (forest, agriculture and urban) within a 250 m wide impact zone. Three sampling points per location were sampled from two depths (5 –15 cm and 20 – 40 cm) using PVC tube and Bou-Rouch method. The results indicate a significant spatial and temporal heterogeneity of measured hyporheic zone components. Physical and chemical parameters of water revealed moderate response to land use. The effect of land use on the amounts of suspendable fine sediments in the hyporheic zone was observed only in the spring season. The effect of land use was significant for in situ R during summer and spring and for ETSA and protein content in all seasons, indicating that land use, such as agriculture, near a stream can affect biogeochemical processes. A relatively high diversity of invertebrates was recognised in the hyporheic zone. Groups such as Nematoda, Oligochaeta, Copepoda and Chironomidae were found in all samples. Within EPT taxa as representatives of occasional hyporheic invertebrates, 35 taxa were identified. Within Copepoda, as representatives of permanent hyporheic invertebrates, 14 Cyclopoida and 19 Harpacticida taxa were identified. Both assemblages were characterised by high abundance of widespread taxa, such as Baetis sp., Leuctra sp., Diacylops cladestinus and Acanthocyclops hispanicus. Statistically significant differences were observed among land uses in Copopoda assemblages but not for EPT assemblages. Calculated metrics on EPT assemblages showed statistically significant differences in land use in the number of EPT taxa, Simpson index and Shannon-Wiener index. Within Copepoda assemblages, the numbers of Copepoda taxa were significantly higher at forest sites. The hyporheic assemblages were relatively well explained by environmental parameters. This thesis presents a comprehensive study of the hyporheic zone, where both structural and functional measures reflected the ecological integrity of the hyporheic zone. The in situ R and ETSA were generally higher in agriculture stream reaches, indicating that hyporheic functioning responded to nutrients and carbon runoff-derived inputs from agricultural activities within the 250 m impact zone. Thus functional parameters in situ R and ETSA were more efficient indicators of land use impacts in the hyporheic zone than physical and chemical parameters. The potential of using hyporheic invertebrates as bioindicators of environmental conditions was confirmed but should be tested with wider gradients of environmental parameters. The results obtained by this study underlined that the hyporheic zone should be integrated as an additional ecological element by assessing the ecological conditions of surface water bodies.
Najdeno v: ključnih besedah
Povzetek najdenega: the responses of abiotic parameters, sediment biofilm characteristics (the in situ respiration (R), potential...
Ključne besede: hyporheic zone, ecosystem functioning, land use, biofilm characteristics, invertebrates
Objavljeno: 02.07.2018; Ogledov: 1569; Prenosov: 61
.pdf Polno besedilo (5,31 MB)

Regulation and controlling the motility properties of Pseudomonas aeruginosa
Fazlurrahman Khan, Dung Thuy Nguyen Pham, Sandra Folarin Oloketuyi, Young-Mog Kim, 2020, pregledni znanstveni članek

Opis: Chronic infections caused by Pseudomonas aeruginosa have been a major concern as their spread and mortality continue to be on the rise. These infections are majorly attributed to biofilm formation via sequential steps where motility plays an essential role in initial attachment of bacterial cells onto biotic and abiotic surfaces, thereby contributing to multi-drug resistance among pathogens. Therefore, attenuating motility properties can be considered as highly potential for controlling P. aeruginosa biofilm formation. This strategy has employed the use of various natural and chemically synthesized compounds. The present review article explained the importance and regulation of different types of motilities properties. Furthermore, it also covered several important alternative approaches using anti-motility agents which could be helpful for controlling P. aeruginosa biofilm-associated infections. Further studies are required for in-depth understandings about the mechanisms of motilities controlling of these molecules at molecular levels.
Najdeno v: ključnih besedah
Povzetek najdenega: ...rise. These infections are majorly attributed to biofilm formation via sequential steps where motility plays...
Ključne besede: Biofilm, Motility, Attenuation, Antibiofilm drugs, Pseudomonas aeruginosa
Objavljeno: 12.01.2021; Ogledov: 55; Prenosov: 0
.pdf Polno besedilo (4,83 MB)

Antibiotics and their different application strategies in controlling the biofilm forming pathogenic bacteria
Fazlurrahman Khan, Dung T N Pham, Sandra Folarin Oloketuyi, Young-Mog Kim, 2020, pregledni znanstveni članek

Opis: Background: The establishment of a biofilm by most pathogenic bacteria has been known as one of the resistance mechanisms against antibiotics. A biofilm is a structural component where the bacterial community adheres to the biotic or abiotic surfaces by the help of Extracellular Polymeric Substances (EPS) produced by bacterial cells. The biofilm matrix possesses the ability to resist several adverse environmental factors, including the effect of antibiotics. Therefore, the resistance of bacterial biofilm-forming cells could be increased up to 1000 times than the planktonic cells, hence requiring a significantly high concentration of antibiotics for treatment. Methods: Up to the present, several methodologies employing antibiotics as an anti-biofilm, antivirulence or quorum quenching agent have been developed for biofilm inhibition and eradication of a pre-formed mature biofilm. Results: Among the anti-biofilm strategies being tested, the sub-minimal inhibitory concentration of several antibiotics either alone or in combination has been shown to inhibit biofilm formation and down-regulate the production of virulence factors. The combinatorial strategies include (1) combination of multiple antibiotics, (2) combination of antibiotics with non-antibiotic agents and (3) loading of antibiotics onto a carrier. Conclusion: The present review paper describes the role of several antibiotics as biofilm inhibitors and also the alternative strategies adopted for applications in eradicating and inhibiting the formation of biofilm by pathogenic bacteria.
Najdeno v: ključnih besedah
Ključne besede: Antibiotics, biofilm inhibition, multiple antibiotics, pathogenic bacteria, resistance mechanism, virulence factors
Objavljeno: 14.01.2021; Ogledov: 25; Prenosov: 0
.pdf Polno besedilo (2,61 MB)

Diversity of bacteria and bacterial products as antibiofilm and antiquorum sensing drugs against pathogenic bacteria
Fazlurrahman Khan, Sandra Folarin Oloketuyi, Young-Mog Kim, 2019, pregledni znanstveni članek

Opis: The increase in antibiotic resistance of pathogenic bacteria has led to the development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing (QS) signaling systems. The QS system is a phenomenon in which pathogenic bacteria produce signaling molecules that are involved in cell to cell communication, production of virulence factors, biofilm maturation, and several other functions. In the natural environment, several non-pathogenic bacteria are present as mixed population along with pathogenic bacteria and they control the behavior of microbial community by producing secondary metabolites. Similarly, non-pathogenic bacteria also take advantages of the QS signaling molecule as a sole carbon source for their growth through catabolism with enzymes. Several enzymes are produced by bacteria which disrupt the biofilm architecture by degrading the composition of extracellular polymeric substances (EPS) such as exopolysaccharide, extracellular- DNA and protein. Thus, the interference of QS system by bacterial metabolic products and enzymatic catalysis, modification of the QS signaling molecules as well as enzymatic disruption of biofilm architecture have been considered as the alternative therapeutic approaches. This review article elaborates on the diversity of different bacterial species with respect to their metabolic products as well as enzymes and their molecular modes of action. The bacterial enzymes and metabolic products will open new and promising perspectives for the development of strategies against the pathogenic bacterial infections.
Najdeno v: ključnih besedah
Povzetek najdenega: ...development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing...
Ključne besede: Bacteria, biofilm, quorum sensing, inhibition, metabolites, pathogen, virulence.
Objavljeno: 18.01.2021; Ogledov: 28; Prenosov: 0
.pdf Polno besedilo (2,17 MB)

Inhibition strategies of Listeria monocytogenes biofilms- Current knowledge and future outlooks.
Sandra Folarin Oloketuyi, Fazlurrahman Khanna, 2017, pregledni znanstveni članek

Opis: There is an increasing trend in the food industry on the Listeria monocytogenes biofilm formation and inhibition. This is attributed to its easy survival on contact surfaces, resistance to disinfectants or antibiotics and growth under the stringent condition used for food processing and preservation thereby leading to food contamination products by direct or indirect exposure. Though, there is a lack of conclusive evidences about the mechanism of biofilm formation, in this review, the concept of biofilm formation and various chemical, physical, and green technology approaches to prevent or control the biofilm formed is discussed. State-of-the-art approaches ranging from the application of natural to synthetic molecules with high effectiveness and non-toxicity targeted at the different steps of biofilm formation could positively influence the biofilm inhibition in the future.
Najdeno v: ključnih besedah
Povzetek najdenega: ...the food industry on the Listeria monocytogenes biofilm formation and inhibition. This is attributed to...
Ključne besede: Listeria monocytogenes, biofilm, food industry, inhibition, pathogen
Objavljeno: 14.01.2021; Ogledov: 34; Prenosov: 0
.pdf Polno besedilo (697,40 KB)
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Treatment strategies targeting persister cell formation in bacterial pathogens
Fazlurrahman Khan, Dung Pham, Nazia Tabassum, Sandra Folarin Oloketuyi, Young-Mog Kim, 2020, pregledni znanstveni članek

Opis: Persister cells are transiently antibiotic-tolerant and dormant subpopulations that are produced to escape the effects of antibiotics within biofilms or planktonic cell populations. Persister cells are of high clinical importance due to their tolerance to antimicrobial agents and subsequent failure in antibiotic treatments. Understanding persister cell formation mechanisms is therefore highly important for developing effective therapeutic strategies against pathogenic bacterial persisters. Several anti-persister compounds have been previously identified via isolation from natural resources or chemical synthesis. Furthermore, a combination of these compounds with antibiotics or non-antibiotic drugs also allows action on multiple targets while reducing the administration frequency. Here, we present a comprehensive overview of the clinical importance and formation mechanisms of persister cells as well as the current treatment strategies against persister cell formations in chronic infections.
Najdeno v: ključnih besedah
Povzetek najdenega: ... Biofilm, anti-persister agents, persister cells, pathogenic bacteria, chronic...
Ključne besede: Biofilm, anti-persister agents, persister cells, pathogenic bacteria, chronic infections
Objavljeno: 14.01.2021; Ogledov: 43; Prenosov: 0
.pdf Polno besedilo (3,31 MB)

Chitosan and their derivatives: Antibiofilm drugs against pathogenic bacteria
Fazlurrahman Khan, Dong Pham, Sandra Folarin Oloketuyi, Panchanathan Manivasagan, Junghwan Oh, Young-Mog Kim, 2020, pregledni znanstveni članek

Opis: Biofilm formed by several pathogenic bacteria results in the development of resistance against antimicrobial compounds. The polymeric materials present in the biofilm architecture hinder the entry of antimicrobial compounds through the surface of bacterial cells which are embedded as well as enclosed beneath the biofilm matrix. Recent and past studies explored the alternative approaches to inhibit the formation of biofilm by different agents isolated from plants, animals, and microbes. Among these agents, chitosan and its derivatives have got more attention due to their properties such as biodegradability, biocompatibility, non-allergenic and non-toxicity. Recent researches have focused on employing chitosan and its derivatives as effective agents to inhibit biofilm formation and attenuate virulence properties by various pathogenic bacteria. Such antibiofilm activity of chitosan and its derivatives can be further enhanced by conjugation with a wide range of bioactive compounds. The present review describes the antibiofilm properties of chitosan and its derivatives against the pathogenic bacteria. This review also summarizes the mechanisms of biofilm inhibition exhibited by these molecules. The knowledge of the antibiofilm activities of chitosan and its derivatives as well as their underlying mechanisms provides essential insights for widening their applications in the future.
Najdeno v: ključnih besedah
Povzetek najdenega: ... Biofilm formed by several pathogenic bacteria results in...
Ključne besede: Antibiofilm, Biofilm inhibition, Chitosan, Chitosan derivatives, Pathogenic bacteria
Objavljeno: 14.01.2021; Ogledov: 39; Prenosov: 0
.pdf Polno besedilo (3,95 MB)

Molecules involved in motility regulation in Escherichia coli cells: a review
Fazlurrahman Khan, Nazia Tabassum, Dung :Pham, Sandra Folarin Oloketuyi, Young-Mog Kim, 2020, izvirni znanstveni članek

Opis: The initial colonization of the host organism by commensal, probiotic, and pathogenic Escherichia coli strains is an important step in the development of infections and biofilms. Sensing and colonization of host cell surfaces are governed by flagellar and fimbriae/pili appendages, respectively. Biofilm formation confers great advantages on pathogenic E. coli cells such as protection against the host immune system, antimicrobial agents, and several environmental stress factors. The transition from planktonic to sessile physiological states involves several signaling cascades and factors responsible for the regulation of flagellar motility in E. coli cells. These regulatory factors have thus become important targets to control pathogenicity. Hence, attenuation of flagellar motility is considered a potential therapy against pathogenic E. coli. The present review describes signaling pathways and proteins involved in direct or indirect regulation of flagellar motility. Furthermore, application strategies for antimotility natural or synthetic compounds are discussed also.
Najdeno v: ključnih besedah
Povzetek najdenega: ...step in the development of infections and biofilms. Sensing and colonization of host cell surfaces...
Ključne besede: Biofilm formation, Escherichia coli, inhibition, motility, pathogenesis
Objavljeno: 14.01.2021; Ogledov: 39; Prenosov: 0
.pdf Polno besedilo (2,42 MB)

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