Foodborne diseases caused by non-typhoidal Salmonella represent an important public health problem worldwide (Zhao et al., 2003). The transmission of Salmonella between animals and humans has been well established in epidemiological studies. In the case of complicated illness caused by Salmonella where antibiotics need to be administered, treatment can be compromised if the infecting organism is resistant to the prescribed antimicrobial agent. This study and earlier studies have shown that many Salmonella carry temperate bacteriophages as lysogens. Many of these bacteriophages are capable of mediating generalised transduction (Schicklmaier and Schmieger, 1995; Schicklmaier et al., 1998; Mmolawa et al., 2002). Schmieger and Schicklmaier (1999) demonstrated that bacteriophages ES18 and PDT17 are capable of transduction of antibiotic resistance genes from DT104. Phage-mediated transduction of antibiotic resistance genes has been largely neglected in the study of genetic transfer of antibiotic resistance in bacteria. This study investigates whether bacteriophages exist in antibiotic resistant Salmonella isolates. Such temperate phages in antibiotic resistant isolates could play a significant role in the transfer of resistance to other species of enteric bacteria, such as E. coli. Molecular epidemiology studies of antibiotic resistance genes were undertaken with Salmonella isolates from chicken, pig and human sources that were subjected to PCR for ampicillin (blaTEM-1), tetracycline (tetA, tetB) and streptomycin (aadA1, aadA2, strA, strB) resistance genes as well as Class 1 integrons. The blaTEM-1 gene was widely detected in isolates from pigs and chickens but rarely detected in human isolates. The tetB gene was more commonly found in pig isolates, while the tetA gene was associated with tetracycline resistance in chicken isolates. The strA and strB genes were responsible for streptomycin resistance in the S. Typhimurium isolates while the aadA1 gene was commonly detected in S. Kiambu and S. Virchow isolates. The aadA2 gene was associated with streptomycin resistance in the S. Ohio isolates from pigs. Class 1 integrons were widely distributed across serovars tested from chicken, pig and human sources. Temperate bacteriophages were induced using mitomycin C from antibiotic resistant Salmonella. These phages were able to infect antibiotic-sensitive Salmonella isolates from humans. Bacteriophages induced from one S. Sofia isolate also plaqued on Shigella flexneri. Bacteriophages induced from one S.Kiambu isolate and S. Typhimurium DB21 with an inserted Tn10 transposon (S. Typhimurium DB21 Tn10) were capable of transducing ampicillin and tetracycline resistance, respectively into S. Enteritidis PT1 isolates by in vitro methods. The molecular basis for resistance was established in subsequent PCR for antibiotic resistance genes in donor and recipient strains. This finding, in particular in the wild-type S. Kiambu strain, indicates that Salmonella from a natural source are able to infect and transfer antibiotic resistance by generalised transduction in controlled laboratory experiments. This current study has investigated the transfer of tetracycline and ampicillin resistance from a wild-type Salmonella strain and a laboratory strain of Salmonella to wild-type Salmonella bacteria as it occurs within the normal flora of the chicken gastrointestinal tract. It was demonstrated that the genetic transfer of tetracycline and ampicillin resistance genes as well as Class 1 integrons can occur within the chicken gastrointestinal tract. Transfer of tetracycline and ampicillin resistance could be demonstrated both in vitro and by using bacteriophage lysates obtained from in vivo studies in transduction experiments. It was clearly shown that bacteriophage isolated from chicken faeces and caeca could infect antibiotic sensitive recipient Salmonella. Interaction between phages of the administered Salmonella strains may be occuring with phages of bacteria in the normal flora allowing previously inactive phage in the indigenous flora to plaque on indicator strains. Additionally, strong evidence was presented to suggest that the environment of the chicken gastrointestinal tract could mediate phage type conversion in recipient and transductant strains. Phage typing of these recipient and transductant strains demonstrated a trend for recipient strains to become more resistant to phages in the S. Enteritidis typing panel. This led to weakened phage reactions such RDNC (reaction does not conform) and untypable. The acquisition of phages may be a way for Salmonella to enhance competitive fitness and generate new strains in order to evolve and diversify. Or the acquisition of plasmids either by transduction or conjugation may also mediate phage type conversion. MLVA typing was performed on selected recipient, donor and transductant strains. The changes to tandem repeat loci in Salmonella isolates that have passed through a chicken gastrointestinal tract have not been described before. The changes to fragment length suggest that the bacterial chromosome is undergoing rearrangement; this may be attributed to a number of factors including acquisition of phages, prophage integration into tRNA sites, slipped-strand mispairing or the adaption to changing environment, in this case the chicken gastrointestinal tract. This study has provided molecular epidemiological data on the antibiotic resistance genes and integrons present in Australian Salmonella isolates from human and animal sources. Information on the role of bacteriophages in the transfer of antibiotic resistance genes in vitro and in a chicken gastrointestinal tract has also been established. / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2010

Thesis (M.S.)--Bowling Green State University, 2008. / Document formatted into pages; contains vi, 48 p. : ill. Includes bibliographical references.

Thesis (Ph.D. in Biochemistry) -- University of Colorado, 2006. / Typescript. Includes bibliographical references (leaves 118-126). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;

Thesis (Ph. D.)--University of Chicago, Dept. of Molecular Genetics and Cell Biology, March 2001. / Includes bibliographical references. Also available on the Internet.

With the spread of antibiotic resistance, alternative treatment methods for bacterial pathogens are needed. Pseudomonas aeruginosa is a Gram negative, opportunistic pathogen that is a common cause of healthcare associated infections and is listed as a critical priority for research and development of treatments by the Centers for Disease Control and Prevention. P. aeruginosa poses an increased risk to patients within the surgical or intensive care unit, patients with indwelling catheters, cystic fibrosis, and burn wound victims. With a paucity of antibiotics in the pipeline for Gram negative bacteria, phage therapy has reemerged as a potential treatment option. Bacteriophages were first discovered in 1917 by Felix d’Herelle, but by the end of World War II, they were all but forgotten in favor of antibiotics. Eastern European countries and the former Soviet Union continued to develop phage therapy since its discovery, but studies were not on par with today’s standards. Recently the idea of phage therapy has reemerged in the Western world due to antibiotic resistance. In vitro and in vivo studies have shown that bacteriophages are easily isolated from the environment, with P. aeruginosa specific phages commonly found in hospital waste water and in sewage. Phage therapy has shown to be very effective at treating planktonic and biofilm forms of antibiotic resistant P. aeruginosa in vitro and in vivo. In humans, clinical trials are limited but phage therapy has successfully treated chronic otitis infections caused by P. aeruginosa and other studies have demonstrated the safety of phage therapy, reporting mild, if any, adverse effects. Bacteriophages may also synergize with several antibiotics, suggesting it may be beneficial to use them in conjunction to treat difficult or chronic infections. Additionally, P. aeruginosa bacteriophages may be beneficial in prophylactic treatment as well. When phages were combined with chlorine, a significant decrease in P. aeruginosa counts in chronic biofilms was observed, while also reducing its ability to form new biofilms. Similar results were noted when phages were applied to the lumen of catheters. These early results are promising for the future, but there are many steps that must be taken before starting new clinical trials and the widespread use of phage therapy begins.

Master of Science / Food Science Institute / Thomas J. Herald / Food recalls and incidence of foodborne disease are on the rise throughout the world. Food products are recalled in the United States almost daily, and typically a large quantity of food is affected. Pathogenic microorganisms are readily invading the food supply and traditional methods and use of antimicrobials are not performing as well as in the past. The microorganisms that prompt the recalls cause symptoms ranging from mild gastroenteritis to death. All humans eat food, therefore all humans have the potential to be exposed to pathogens in food at some point in their life. There is a need for new, more effective antimicrobials for use on food products in order to ensure that consumers have access to a safe food supply. Any new treatments for prevention of pathogenic growth in the food supply should be researched. Phage preparations used as antimicrobials on food products are a novel idea. Phages are advantageous over traditional antimicrobials such as antibiotics, pesticides, and sanitizers in numerous ways. This report presents the history of phage and phage therapy in humans, advantages and disadvantages of phage use over traditional methods, current phage preparations available or under research, and approvals and objections of phage use in the food supply.

Biofouling and biocorrosion are due to unwanted deposition of microorganisms on surfaces that are exposed to different types of water. This dissertation focuses on the application of innovative strategies to inhibit biofouling and biocorrosion. Specifically, the strategies examined in this dissertation, namely the use of bacteriophages and quorum quenchers, aim to minimize reliance on the conventional chemical cleaning agents and to reduce chemical-induced hazards on health, safety and environment. First, we analyzed the use of bacteriophages to remove biofoulants on ultrafiltration membrane used in seawater reverse osmosis pretreatment. Our findings revealed that bacteriophages were able to remain active against membrane-associated Pseudomonas aeruginosa at a broad range of temperature, pH and salinity. Bacteriophages were also shown to inhibit biofilm and to reduce transmembrane pressure increment, when applied alone or in combination with chemical agents. Second, this dissertation explores the use of quorum quenchers to inhibit biocorrosion in seawater environment. To do so, we first examined for the presence of quorum sensing system in sulfate reducing bacteria (SRB). Through transcriptomic analysis, we further demonstrate a strong correlation between quorum sensing, biofilm formation and biocorrosion. Therefore, the use of quorum sensing inhibitors was suggested to prevent biofilm formation and biocorrosion caused by SRB in seawater. Through findings from Chapter 2 and 3, we introduced the use of alternative biocidal agents to tackle biofouling and biocorrosion. Compared to quorum quenchers, bacteriophages showed better antibiofilm potential and easier applicability at larger scale. However, bacteriophages alone were insufficient to reduce biofilm formation as phage resistance was observed over long-term experiments. Hence in the last chapter, we further explored the use of bacteriophages to alleviate biofouling that occurred during wastewater treatment process, by combining their infection with UV irradiation. UV was used both for its biocidal effect and to trigger phage infection against bacteria. Our findings indicate that the combined treatment was able to remove mature biofoulants from the membrane. Overall, this dissertation demonstrates the use of bacteriophages and quorum quenchers against biofilm. These two approaches can serve to reduce the amount of chemicals used during cleaning, thus providing a more sustainable way of minimizing biofilm-associated problems.

<p> Temperature-sensitive mutants of the bacteriophage PBS 2 were isolated from lysates treated with various mutagens. Complementation tests assigned the mutants to 10 cistrons. The mutants were mapped by two factor crosses and formed a linear map approximately 50 recombination percent in length. </p> <p> A method for phage transformation was developed. By the use of wild type DNA fragments fractionated according to their guanine + cytosine content in HgCs₂SO₄ gradients, it was possible to determine the base composition of certain regions of the chromosomes. </p> / Thesis / Doctor of Philosophy (PhD)

No abstract provided. / Thesis / Doctor of Philosophy (PhD)

No description available.