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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Environmental fate of Chlortetracycline, Sulfamethazine and Tylosin fed to feedlot cattle

Amarakoon Mudiyanselage, Inoka January 2014 (has links)
Antimicrobials are widely used in North America’s livestock industry. Field application of livestock manure disperses antimicrobials in to the environment. Antimicrobials can increase the level of antimicrobial resistance development in human and livestock pathogens. Three main studies were conducted to: i) quantify the simulated rain runoff losses of chlortetracycline, sulfamethazine and tylosin following surface application vs. soil incorporation of beef cattle feedlot manure; ii) quantify the dissipation kinetics of these antimicrobials in a seasonally-frozen soil following field application of manure; and iii) quantify and compare the dissipation of excreted vs. fortified (that is, added to antimicrobial-free manure) antimicrobials during indoor composting. Manure was sourced from cattle (Bos taurus) receiving no antimicrobial (control), 44 mg chlortetracycline, 44 mg each of chlortetracycline and sulfamethazine, or 11 mg tylosin per kg-1 feed. Antimicrobial concentration in simulated rain runoff following field application of manure generally reflected the corresponding concentrations in manure. Mass loss ranged from 1.7 to 6.5% for chlortetracycline and was 4.8% for sulfamethazine and 0.24% for tylosin. Incorporation of manure into the top 10 cm of soil significantly reduced the mass loss of chlortetracycline and the concentration in runoff of both chlortetracycline and sulfamethazine. Both chlortetracycline and sulfamethazine were persistent in the seasonally-frozen Canadian prairie soil tested. The first-order dissipation half-life (DT50) for chlortetracycline added along with sulfamethazine was 77 d during the growing season and 648 d during the non-growing season. The DT50 of chlortetracycline added alone did not differ significantly between the two seasons (mean DT50 = 121 d). Sulfamethazine was detected throughout the 10-mo monitoring period (mean ≤ 16 ± 10 µg kg-1). Composting dissipated 85–99% of initial concentrations of chlortetracycline, sulfamethazine, and tylosin in manure within 30 d, indicating the potential of composting to minimize the dispersal of these antimicrobials in agroecosystems. The first-order dissipation constant (k) was significantly greater for excreted chlortetracycline (0.29 d-1 - 0.54 d-1) than for the fortified (0.11 d-1 - 0.13 d-1) compound. In contrast, dissipation was significantly greater for fortified sulfamethazine (0.47 d-1) and tylosin (0.31 d-1) than for the excreted antimicrobials (0.08 d-1 for sulfamethazine and 0.07 d-1 for tylosin). / October 2016
2

The role of microbial biofilm adherent to endotracheal tuber in nocosomial pneumonia

Feron, Barbara Maria Ellen January 1994 (has links)
No description available.
3

The Bioactive Properties of Syringomycin E-Rhamnolipid Mixtures and Syringopeptins

Bensaci, Mekki F. 01 May 2009 (has links)
The need for new antimicrobial agents has become important in the last decade due to emerging resistance to a number of conventional antimicrobial agents. New approaches and sources are needed to generate novel and effective antimicrobials. For example, synergistic combinations between two or more agents may lead to new antimicrobial therapies. Furthermore, the increase in health problems caused by the exposure to agricultural crop pesticides and synthetic fungicides and the emerging development of organic farming has increased the necessity to develop natural products than can be used safely in controlling crop diseases. In this work, I present the first studies on the bioactive properties, particularly fungicidal activities, of mixtures of SRE and rhamnolipids. The in vitro results clearly showed strong synergism between SRE and rhamnolipids against phytopathogenic fungi and yeast. However, no activity was observed against bacteria. The hemolytic activities and cytotoxicities of SRE and SYRA were dose dependent. SRE acts on yeast and plant plasma membranes to cause numerous cellular effects. The effects are consistent with SRE's ability to form ion-conducting voltage sensitive channels in membrane bilayers. In addition, studies with yeast have revealed that sphingolipids and sterols modulate the fungicidal activity of SRE. Saccharomyces cerevisiae sphingolipid and sterol biosynthetic mutants were used to investigate the mechanism of action of SYRA against fungi. These results suggest that similar to SRE, SYRA antifungal action is promoted by sphingolipids and sterols of the plasma membrane and involves pore formation. I further explored the antimicrobial spectrum of syringopeptin SP25A and show that it specifically inhibits Gram-positive bacteria and yeast. I also investigated its mechanism of action against yeast and bacteria. The results revealed the role for D-alanylation of teichoic acids in modulating the susceptibility of B. subtilis to SP25A and other syringopeptins. This is consistent with the charged nature of the cyclic peptide portions of the syringopeptins, and it provides an explanation for SP25A's higher degree of specificity for Gram-positive bacteria. In addition and similar to SRE, SP25A antifungal action is promoted by sphingolipids and sterols of the plasma membrane and involves pore formation. Overall, the research shows that SRE and rhamnolipids are synergistically active against yeast and fungi and that the syringopeptins have antimicrobial activities against yeast and Gram-positive bacteria. Insights into the mechanisms of action of the SRE and rhamnolipid mixtures and the syringopeptins and their potential as novel antimicrobial agents are revealed.
4

The Efficacy of Antimicrobials for the Control of Alicyclobacillus acidoterrestris in Fruit and Vegetable Juices

Hartman, Angela Danielle 03 July 2003 (has links)
The efficacy of antimicrobials for control of A. acidoterrestris spoilage in juices was analyzed. Apple and tomato juices were inoculated with 4 log spores/ml. Antimicrobials were added at: 1000, 500 and 250 ppm (sodium benzoate, potassium sorbate, and sodium metabisulfite); 500, 250, and 125 ppm (cinnamic acid, dimethyl dicarbonate, and ascorbic acid); 125, 75 and 25 ppm (lysozyme); and 5, 3, and 1 IU/ml (nisin). In apple juice, A. acidoterrestris population reductions were caused by the following antimicrobials (reduction in log CFU/ml): lysozyme - all levels and nisin - 5 IU/ml (5.1), nisin - 3 IU/ml (4.2), cinnamic acid - 125 ppm (3.1), cinnamic acid - 250 ppm (2.6), potassium sorbate - 250ppm (2.5), nisin - 1 IU/ml (2.4), potassium sorbate - 500 and 1,000 ppm (2.3), dimethyl dicarbonate - 500 ppm (1.9), cinnamic acid - 500 ppm (1.4). In tomato juice, A. acidoterrestris population reductions were caused by the following antimicrobials (reduction log CFU/ml): nisin - all levels and lysozyme - 125 ppm and 75 ppm (4.4), lysozyme - 25 ppm (3.8), potassium sorbate - 500 ppm (2.6), cinnamic acid - 500 ppm (2.5), cinnamic acid - 250 ppm (2.4), cinnamic acid - 125 ppm (2.1), potassium sorbate - 1,000 ppm (1.9), and potassium sorbate - 250 ppm (1.6). Antimicrobial treatments: nisin - ≥ 1 IU/ml, lysozyme - ≥ 25 ppm, cinnamic acid - ≥ 125 ppm, and potassium sorbate - ≥ 250 ppm may be appropriate controls to prevent A. acidoterrestris spoilage in juices or juice containing beverages. / Master of Science
5

A phylum level analysis reveals lipoprotein biosynthesis to be a fundamental property of bacteria

Sutcliffe, I.C., Harrington, Dean J., Hutchings, M.I. 03 October 2012 (has links)
No / Bacterial lipoproteins are proteins that are post-translationally modified with a diacylglyceride at an N-terminal cysteine, which serves to tether these proteins to the outer face of the plasma membrane or to the outer membrane. This paper reviews recent insights into the enzymology of bacterial lipoprotein biosynthesis and localization. Moreover, we use bioinformatic analyses of bacterial lipoprotein signal peptide features and of the key biosynthetic enzymes to consider the distribution of lipoprotein biosynthesis at the phylum level. These analyses support the important conclusion that lipoprotein biosynthesis is a fundamental pathway utilized across the domain bacteria. Moreover, with the exception of a small number of sequences likely to derive from endosymbiont genomes, the enzymes of bacterial lipoprotein biosynthesis appear unique to bacteria, making this pathway an attractive target for the development of novel antimicrobials. Whilst lipoproteins with comparable signal peptide features are encoded in the genomes of Archaea, it is clear that these lipoproteins have a distinctive biosynthetic pathway that has yet to be characterized.
6

Effect of natural antimicrobials against Salmonella, Escherichia coli o157:h7 and Listeria monocytogenes

Cuervo Pliego, Mary Pia 15 May 2009 (has links)
Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes are pathogens that have caught the attention of federal agencies and researchers due to their great economic impact when illnesses occur. To reduce the presence of these pathogens, different approaches have been used. However, since the global consumer’s demand for natural ingredients is steadily increasing, the investigation of the effectiveness of potential natural antimicrobials is necessary. In this study, the in vitro antimicrobial activity of Hibiscus sabdariffa L extracts against Salmonella, E. coli O157:H7 and L. monocytogenes was investigated. Furthermore, H. sabdariffa L and ε-polylysine were evaluated to reduce populations of Salmonella and E. coli O157:H7 in ground beef. The minimum inhibitory concentration (MIC) of H. sabdariffa L extracts against Salmonella and E. coli O157:H7 was 6,489 μg/mL and for L. monocytogenes, 5,309 μg/mL. The minimum bactericidal concentration (MBC) of H. sabdariffa L extracts against Salmonella, E. coli O157:H7 and L. monocytogenes was 19,467, 58,400 and 29,200 μg/mL, respectively. The exposure to 58,400 μg/mL of H. sabdariffa extract at 25 oC for 12 h resulted in reductions of more than 6.0 log CFU/mL for any of the 3 pathogens tested. Ground beef inoculated with S. Agona (GFP) and E. coli O157:H7 (RFP) was subjected to 5 decontamination treatments. Three of the treatments were using H. sabdariffa L and the remaining ε-polylysine. S. Agona (GFP) was reduced in 1.1 log cycles using 10% of ground H. sabdariffa L and E. coli O157:H7 (RFP) was reduced 0.9 log cycles using 400 ppm of ε-polylysine. If these natural antimicrobials are combined with current antimicrobial technologies to form a hurdle effect, higher pathogen reductions could be achieved. Reductions in the presence of pathogens in food may lead into reductions in the incidence of foodborne diseases.
7

Effect of natural antimicrobials against Salmonella, Escherichia coli o157:h7 and Listeria monocytogenes

Cuervo Pliego, Mary Pia 15 May 2009 (has links)
Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes are pathogens that have caught the attention of federal agencies and researchers due to their great economic impact when illnesses occur. To reduce the presence of these pathogens, different approaches have been used. However, since the global consumer’s demand for natural ingredients is steadily increasing, the investigation of the effectiveness of potential natural antimicrobials is necessary. In this study, the in vitro antimicrobial activity of Hibiscus sabdariffa L extracts against Salmonella, E. coli O157:H7 and L. monocytogenes was investigated. Furthermore, H. sabdariffa L and ε-polylysine were evaluated to reduce populations of Salmonella and E. coli O157:H7 in ground beef. The minimum inhibitory concentration (MIC) of H. sabdariffa L extracts against Salmonella and E. coli O157:H7 was 6,489 μg/mL and for L. monocytogenes, 5,309 μg/mL. The minimum bactericidal concentration (MBC) of H. sabdariffa L extracts against Salmonella, E. coli O157:H7 and L. monocytogenes was 19,467, 58,400 and 29,200 μg/mL, respectively. The exposure to 58,400 μg/mL of H. sabdariffa extract at 25 oC for 12 h resulted in reductions of more than 6.0 log CFU/mL for any of the 3 pathogens tested. Ground beef inoculated with S. Agona (GFP) and E. coli O157:H7 (RFP) was subjected to 5 decontamination treatments. Three of the treatments were using H. sabdariffa L and the remaining ε-polylysine. S. Agona (GFP) was reduced in 1.1 log cycles using 10% of ground H. sabdariffa L and E. coli O157:H7 (RFP) was reduced 0.9 log cycles using 400 ppm of ε-polylysine. If these natural antimicrobials are combined with current antimicrobial technologies to form a hurdle effect, higher pathogen reductions could be achieved. Reductions in the presence of pathogens in food may lead into reductions in the incidence of foodborne diseases.
8

Studies on the mode of action of the pyrithione biocides

Dinning, Anthony Joseph January 1995 (has links)
No description available.
9

Assessing beef hide interventions as a means to reduce carcass contamination

Baird, Bridget Elaine 25 April 2007 (has links)
Food safety is a critical issue for beef harvest operations. There are multiple interventions available for treating carcasses; however, this project was designed to evaluate an intervention capable of reducing bacterial counts on the hide prior to opening in order to minimize carcass contamination. In Trial I, fresh beef hides (n = 12) were cut into sections and assigned to serve as either clipped (hair trimmed) or non-clipped sections. Sections were inoculated with a bovine fecal slurry and sampled following a water wash. Treatments (distilled water, isopropyl alcohol, 3% hydrogen peroxide, 2% L-lactic acid, 1% cetylpyridinium chloride (CPC), and 10% Povidone-iodine) then were applied to each section and sampled for aerobic plate counts (APCs), coliform, and Escherichia coli counts. Within clipped samples, 1% CPC and 3% hydrogen peroxide caused the greatest reductions in aerobic plate counts, and 1% CPC, 2% L-lactic acid, and 3% hydrogen peroxide showed among the greatest reductions in coliform counts. In Trial II, beef carcasses with hides on were sampled initially and clipped, and then antimicrobials (2% L-lactic acid, 3% hydrogen peroxide, and 1% CPC) were applied before sampling again for APC, coliform, and E. coli counts. This procedure was replicated in Trial II utilizing a non-pathogenic E. coli Type I indicator strain transformed to produce a green fluorescing protein (GFP). In Trial II, though few differences existed between antimicrobial treatments, all three (1% CPC, 2% L-lactic acid, and 3% hydrogen peroxide) resulted in approximately a 2-log10 CFU/100-cm2GFP reduction when applied to clipped hide surfaces in the brisket region of the carcass. In Trial III, 1% CPC produced the greatest reduction on the hide surface for APCs. In Trial IV clipped beef hide sections were sampled initially and then antimicrobials (2% L-lactic acid, 3% hydrogen peroxide, and 1% CPC) were applied before sampling again to determine reduction. Trial IV also involved the use of the E. coli GFP indicator strain. In Trial IV, non-clipped samples had a mean reduction of 2.8 log10 CFU/100 cm2, and clipped samples had a mean reduction of 2.2 log10 CFU/100 cm2. Within the antimicrobials tested, 1% CPC and 3% hydrogen peroxide produced the greatest reductions.
10

Hidden Antimicrobials in Surgical Patients: Usage and Documentation of Antimicrobial Content of Bone Cement

Ortega, Alicia, Puracan, Janssen, Torner, Jamie, Matthias, Kathryn January 2012 (has links)
Class of 2012 Abstract / Specific Aims: To evaluate surgery, infectious disease, and nephrology consult documentation of antimicrobial content in bone cement within 30 days post-surgery; evaluate documentation of antimicrobial cement content by pharmacists in pharmacokinetic drug level evaluations within 6 months post-surgery; assess frequency and severity of adverse drug events associated with antimicrobials in bone cement. Methods: Retrospective chart review, which utilized a data collection form to evaluate the dose and type of antimicrobial agents prescribed, median and range antimicrobial doses per 40 grams of cement, documentation rates of antimicrobial content in clinical notes and incidence of potential adverse drug effects. Subjects were identified based on an ICD-9 code and their electronic medical records were accessed. Main Results: The sample size was 24 patients. The surgery notes had the highest rates of documentation with 96% naming the drug and 75% included the dose. The rates were the same in the infectious diseases consults and pharmacy pharmacokinetics notes with the drug name at 27% and the dose at 9%. No nephrology consult notes mentioned antimicrobials contained in the cement. Renal dysfunction (sCr≥2) developed in 13% of patients within 30 days and 25% of patients within 100 days. Approximately 17% of patients with renal dysfunction had the antimicrobial-laden cement removed. Conclusions: A variety of antimicrobial agents were embedded in bone cement at various concentrations and documentation from multiple sources was inconsistent. Likewise, adverse events associated with antimicrobial containing bone cement are not consistent.

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