Pathogenic Microbiology Commons^™

Super-Killers: Environmental Isolates That Antagonize Pathogenic Vibrio, Abigail Joy

Honors Projects

Vibrio are members of a bacterial group that thrive in diverse aquatic environments including on the surface of aquatic animals, free-living in the water column, and in association with suspended particles. The total Vibrio counts in the coastal ocean ranges from 10³-10⁵ per milliliter of water depending on seasons and water temperature. Although many different species of Vibrio persist in the water column, pathogenic strains, such as Vibrio cholerae and Vibrio parahaemolyticus are absent or rare in marine environments. We hypothesize that the low abundance of these pathogenic species may be due to interspecific competition among environmental …

Design And Testing Of Novel Anthrax Vaccines Utilizing A Tobacco Mosaic Virus Expression System, Ryan C. Mccomb

KGI Theses and Dissertations

Anthrax is a potentially fatal disease caused by the bacteria Bacillus anthracis. Infection and disease occur after spores gain entry into the body, germinate into vegetative bacteria, and produce toxin. Bacillus anthracis spores have been engineered as bioweapons and have been used repeatedly in warfare and terrorism to inflict casualties in military and civilian populations. Currently, only one vaccine has been approved for prevention of anthrax in the United States. This vaccine is an undefined product that is difficult to produce, requires a long vaccination schedule, and is reactogenic. Efforts to make an improved anthrax vaccine are being pursued. …

Characterization Of The Reconstituted And Native Pseudomonas Aeruginosa Type Iii Secretion System Translocon, Kathryn R. Monopoli

Masters Theses

The Type III Secretion (T3S) system is a system utilized by many pathogenic bacteria to inject proteins into host cells during an infection. Effector proteins enter the host cell by passing through the proteinaceous T3S translocon, which forms a pore on the host cell membrane. Pseudomonas aeruginosa is an opportunistic pathogen that utilizes the T3S system, and very little is known about how the P. aeruginosa translocon forms.

The proteins PopB and PopD are believed to assemble into the P. aeruginosa translocon. A pore-forming heterocomplex of PopB and PopD has been reconstituted in model membranes, however this heterocomplex has not …

The Role Of Phosphatidylserine And Phosphatidylethanolamine In Candida Albicans Virulence, Sarah Elizabeth Davis

Doctoral Dissertations

In hospitalized patients with neutropenia, Candida albicans is the fourth leading cause of systemic bloodstream infections, which have a mortality rate of approximately 30 %. The phosphatidylserine synthase enzyme of C. albicans, Cho1p, appears to be a good drug target as a mutant lacking this enzyme (the cho1Δ/Δ [null mutant]) is avirulent in animal models of Candida infections and this enzyme is not conserved in humans. We discovered that the loss of phosphatidylserine (PS) synthesis affects C. albicans' expression of the Als3p adhesin, a virulence protein, and loss of PS synthesis also compromises the cell wall, causing increased …

Prevalence Of A Chytrid Pathogen (Batrachochytrium Dendrobatidis) In Eastern Hellbender Salamanders In New York And Pennsylvania, Linxuan Wu

Biology Theses

Amphibian populations are currently declining globally. There are many possible causes for these declines, among which an emerging infectious disease, chytridiomycosis, has been implicated. Chytridiomycosis in the U.S.A. is mainly caused by the Batrachochytrium dendrobatidis. In this study, I used qPCR assays to detect the existence of this pathogen in the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) populations in the Allegheny and Susquehanna River drainages of New York and Pennsylvania. Chytrid is most often tested by using skin swabs, but in this study, tail clips, dorsal skin, blood and eggs were tested as well. Batrachochytrium dendrobatidis was detected …

Regulation Of Vancomycin Resistance And Stress Response By The Msaabcr Operon In Staphylococcus Aureus, Dhritiman Samanta

Dissertations

Staphylococcus aureus is the predominant cause of public health problems around the world. Vancomycin has been an important antibiotic against Methicillin Resistant Staphylococcus aureus (MRSA) infections. However, Vancomycin Intermediate S. aureus (VISA) strains have been reported. These strains are characterized by thick cell walls, reduced autolytic rate, reduced PBP4 activity, and increased amount of D-Ala-D-Ala termini in the cell wall. In this study, we show that the msaABCR operon regulates vancomycin resistance in two clinical VISA strains. Deletion of the msaABCR operon in strains Mu50 and HIP6297 resulted in a significant decrease in the minimum inhibitory concentration (MIC) for vancomycin. …

Investigations Of Filarial Nematode Motility, Response To Drug Treatment, And Pathology, Charles Nutting

Dissertations

More than a billion people live at risk of chronic diseases caused by parasitic filarial nematodes. These diseases: lymphatic filariasis, onchocerciasis, and loaisis cause significant morbidity, degrading the health, quality of life, and economic productivity of those who suffer from them. Though treatable, there is no cure to rid those infected of adult parasites. The parasites can modulate the immune system and live for 10-15 years. Testing of compounds against filarial nematodes is complicated due to a lack of an objective platform on which to analyze in vitro treatments. There is no published, immunocompetent laboratory model for lymphatic filariasis. This …

Algr Directly Controls Rsma In Pseudomonas Aeruginosa, Tyler Speaks

Electronic Theses and Dissertations

Pseudomonas aeruginosa is a bacterial pathogen that can infect any human tissue. The lungs of cystic fibrosis patients become chronically infected with Pseudomonas aeruginosa. Virulence factor gene expression is under elaborate regulatory control that remains poorly characterized. Understanding the regulatory hierarchy involved during infection is essential for identifying novel drug targets. RsmA is a post-transcriptional regulatory protein that controls expression of several virulence factors. Previous studies demonstrated alginate regulatory components AlgU and AlgR as regulators of rsmA expression. The aim of this study was to determine how AlgR controls rsmA expression. Western blot analysis of HA-tagged RsmA confirmed lower …

Streptococcus Pyogenes Superantigens: Studies Into Host Specificity And Functional Redundancy, Adrienne T. Wakabayashi

Electronic Thesis and Dissertation Repository

Streptococcus pyogenes is a human-specific globally prominent bacterial pathogen that secretes extremely potent exotoxins known as superantigens. Superantigens function to overstimulate T lymphocytes, capable of inducing excessive cytokine responses, potentially leading to toxic shock syndrome. Each strain of S. pyogenes encodes multiple distinct superantigens, yet the reasons why S. pyogenes retains multiple superantigens has remained elusive. Using a murine model of acute nasopharyngeal infection, the role of each superantigen encoded by S. pyogenes MGAS5005 was evaluated using isogenic superantigen-deletion or -complemented strains, and passive immunization with superantigen-neutralizing antibodies. The superantigen SpeG, and likely SpeJ, were not required for infection. However, …

Virulence Gene Expression Of Vibrio Parahaemolyticus In The Viable But Nonculturable State, Tiffany Pui-Yun Tse

Master's Theses

Vibrio parahaemolyticus is a food-borne pathogen commonly associated with the consumption of raw or undercooked seafood resulting in primary infections of the human gastrointestinal tract. It is estimated to cause about 4500 illnesses each year in the United States. However, infection from this food-borne pathogen can be avoided if this organism is detected in the implicated food, prior to consumption. Current standard methods of detecting this organism are dependent on the culturability of the bacteria. Detection based on an organism’s culturability may be problematic as V. parahaemolyticus has been known to exist in a viable but nonculturable (VBNC) state. Bacteria …

Transduction As The Method Of Horizontal Gene Transfer Of The Staphylococcal Chromosomal Cassette Mec (Sccmec), Amber B. Sauder

Senior Honors Projects, 2010-2019

Methicillin-resistant Staphylococcus aureus (MRSA) gains resistance to β-lactam antibiotics through a mutated penicillin binding protein (PBP2a) encoded on the SCCmec element. In combination with the recombinase encoded by ccr, these two genes are used as markers of the mobile genetic element (SCCmec). Due to recent increases in community acquired MRSA infections, the mechanisms of antibiotic resistance gene transfer have gained attention. Transduction, a method of horizontal gene transfer mediated by bacteriophage, is believed to be responsible for the movement of the SCCmec element. Recent studies have shown the transduction of the SCCmec element in clinical isolates; however, this study is …

Tonb Not Directly Related To Efflux Of Antibiotics In E. Coli, Amber Gombash

Honors Projects

Studies in Pseudomonas aeruginosa have suggested that the TonB energy transduction system directly contributes to efflux-mediated antibiotic resistance, ostensibly by energizing one or more efflux systems. We have found ∆tonB strains of Escherichia coli to similarly be more sensitive to certain antibiotics relative to wild-type strains. To test the hypothesis that this enhanced sensitivity involved the energization of efflux systems, sensitivity patterns for a variety of antibiotics were evaluated using a set of strains differentially lacking genes encoding the Acr efflux system, the universal outer membrane efflux portal TolC, and TonB. No correlation was evident between the resistance phenotypes of …

Genetic Diversity, Population Structure, And Evolution Of Virulence In Toxoplasma Gondii, Elliot Keats Cullen Shwab

Doctoral Dissertations

Toxoplasma gondii is among the most widespread eukaryotic pathogens known. It chronically infects approximately one third of the world’s human population and has been isolated from an extremely diverse array of globally distributed mammals and birds. Understanding the structure of the worldwide T. gondii population enhances our understanding of the factors that have shaped that structure and led to the proliferation of one of the most evolutionarily successful pathogens on Earth. Herein we collate genotypic data from global isolates, demonstrating that T. gondii possesses a unique population structure in which only a small number of genotypes dominate throughout the northern …

Thermal Inactivation Of Shiga Toxin-Producing Escherichia Coli In Foods, Malcond David Valladares

Doctoral Dissertations

Emerging non-O157 Shiga toxin-producing Escherichia coli (STEC) were recently added to the zero tolerance policy by the USDA-FSIS. Therefore, the precise characterization of their thermal inactivation kinetics in different foods and the effect of stress on thermal inactivation are needed. This research aimed at determining the heat inactivation kinetics of non-O157 and O157 STECs in buffer and model food matrices and the effects of DnaK levels on thermal resistance after acid and heat-shock. Thermal inactivation was carried out in either in 2-ml glass vials or nylon vacuum-sealed bags for buffer and food (spinach, ground-beef, turkey deli-meat, pasta) samples, respectively. Vials …

Study Of The Hydrophobin Genes In Verticillium Dahliae And Characterization Of The Hydrophobin Gene Vdh5, Nadia P. Morales

Electronic Thesis and Dissertation Repository

The broad host range, soil borne fungus Verticillium dahliae Kleb. is the causal agent of an economically significant vascular wilt disease. This species produces persistent resting structures, known as microsclerotia, which are the primary source of disease inoculum in the field. Five hydrophobin-like proteins (VDH1 to 5) have been identified in the genome of V. dahliae. The results of bioinformatics analyses suggested secretion of these proteins, and that they are all class II hydrophobins. Gene expression analyses of VDH1 to 5 indicate that the transcript levels of the individual genes vary under different growth conditions. Additionally, the transcript levels of …

Eneterotoxigenic Bacillus Cereus And Bacillus Thuringiensis Spores In U.S. Retail Spices, Upasana Hariram

Masters Theses

Bacillus cereus is a ubiquitous organism and a potential foodborne pathogen that can cause two types of gastrointestinal diseases: emesis and diarrhea. The emetic syndrome is caused by a heat and acid stable peptide toxin that is pre-formed in food, while the diarrheal syndrome is associated to two 3-protein, heat labile enterotoxin complexes that are formed in the intestine after ingestion of the organism. There are many reports on the isolation and characterization of Bacillus cereus from various foods, however there are no studies on the levels, toxigenicity and physical characteristics of B. cereus isolated from U.S. retail spices. …

The Characterization Of A Putative Virulence Factor Expressed By Sneathia Amnii, Amy Sanford

Theses and Dissertations

Preterm birth, defined at birth before 37 weeks gestation, affects millions of newborns worldwide every year. Preterm birth is a leading cause of infant morbidity and mortality. One major cause of preterm birth is preterm premature rupture of membranes (PPROM), which can be triggered by bacterial infection and inflammation. A bacterial species that has been implicated in preterm birth and other obstetric complications is Sneathia amnii. The goals of this study were to observe cytopathogenic effects caused by S. amnii strain Sn35 and identify putative virulence factors causing those effects. Sn35 was able to adhere to, invade, and damage/kill …

Antimicrobial Efficacy Of Natural Bioactive Compounds And High Pressure Processing Against Potential Pathogens In Infant Foods, Hayriye Cetin-Karaca

Theses and Dissertations--Animal and Food Sciences

This study investigated the antimicrobial efficacy of bioactive plant compounds along with high pressure processing (HPP) against pathogens Bacillus cereus and Cronobacter sakazakii in infant formula and infant rice cereal. The influence of these applications on antimicrobial activity, shelf-life and sensory attributes of infant foods were examined.

Trans-cinnamaldehyde (TC), (-)-Epigallocatechin gallate (EGCG) and [10]-Gingerol (GI) were incorporated (0.05%) in infant rice cereal reconstituted with infant formula. The cereal was inoculated with either B. cereus (ATCC 14579) or B. cereus spores (10⁷-10⁸ log CFU g^-1). All the samples were stored at 7, 23 or 37°C for …

The Effect Of O Antigen Loss On The Protein Composition And Inflammatory Response Elicited By Klebsiella Pneumoniae, Bethaney Cahill

UNF Graduate Theses and Dissertations

Klebsiella pneumoniae is a Gram-negative pathogen associated with numerous infections. Like all Gram-negative bacteria, K. pneumoniae naturally release outer membrane vesicles (OMVs) during all stages of cellular growth. OMVs are composed of the outer membrane components such as lipopolysaccharide (LPS) and outer membrane proteins and contain cytosolic and periplasmic proteins in the lumen. K. pneumoniae is often found to lack an O antigen. The absence of the O antigen has been reported to alter the protein content of the membrane which may further alter the immune response elicited by K. pneumoniae. Therefore the purpose of this study was to …

Purification And Characterization Of Bcsc; An Integral Component Of Bacterial Cellulose Export, Emily D. Wilson Ms

Theses and Dissertations (Comprehensive)

Biofilms are a growing concern in the medical field due to their increased resistance to antibiotics. When found in a biofilm, bacteria can have antibiotic resistance 10-1000 times that of their planktonic counterparts. Therefore, it is important to study the formation of biofilms. Cellulose biofilms are formed by Enterobacteriaceae, such as many Escherichia coli and Salmonella spp. strains. Biofilms provide these species with benefits including antimicrobial protection, development of bacterial communities, promotion of DNA exchange, uptake of nutrients, and, in the case of cellulose biofilms, immune system evasion. Cellulose biofilms are controlled by the Bacterial cellulose synthesis (Bcs) complex located …

Characterization Of The Interactions Between Staphylococcal Phage 80 Alpha Scaffold And Capsid Proteins, Laura Klenow

Theses and Dissertations

Staphylococcal phage 80α can serve as a helper bacteriophage for a family of mobile genetic elements called Staphylococcus aureus pathogenicity islands (SaPIs). The prototype island, SaPI1, is able to hijack the 80α capsid assembly process and redirect capsid formation to yield smaller, phage-like transducing particles carrying SaPI DNA. Capsid size redirection is accomplished through two SaPI1-encoded gene products, CpmA and an alternate scaffold protein, CpmB. The normal 80α scaffold and the SaPI1 CpmB scaffold share a small block of conserved residues at their C-termini, several of which had been shown to be essential for CpmB function. This led to the …

Identification Of The Molecular Mechanisms Governing The Osmotolerance Of The Emerging Gastrointestinal Pathogen Cronobacter Sakazakii, Audrey Feeney

Theses

Cronobacter sakazakii is an organism which has been associated with severe life- threatening diseases in infants and neonates. Mortality rates of up to 80% have been recorded in infants infected with Cronobacter sakazakii. Infants often suffer from septicaemia, necrotising enterocolitis and meningitis as a result of infection. A characteristic feature of the opportunistic foodborne pathogen Cronobacter sakazakii is its ability to survive in extremely arid environments such as powdered infant formula, making it a dangerous opportunistic pathogen of neonates. Herein, we provide a brief overview of the pathogen; clinical manifestations, environmental reservoirs and our current understanding of stress response mechanisms …

Exploiting Bacteriophages And Associated Peptidoglycan Hydrolases With Potential For Biocontrol In Food Related Applications, Lorraine Endersen

Theses

The work presented in this thesis describes the isolation and characterisation of novel bacteriophages, and the subsequent exploitation of their bactericidal properties against two opportunistic food related pathogens, Mycobacterium avium subsp. paratuberculosis (MAP) and Cronobacter sakazakii.

MAP is a proven animal pathogen known to cause Johne’s disease in cattle but has been implicated as a causative agent of Crohn’s disease in humans. Despite the fact that this association has yet to be proven, significant focus has been directed towards evaluating the consequences of consuming milk contaminated with MAP. Accordingly, six mycobacteriophages were isolated and characterised in terms of temperature and …

The Effect Of Antibiotics On Pseudomonas Aeruginosa Biofilm Production, Courtney Paige Turpin

Online Theses and Dissertations

Antibiotic-resistant bacteria have become an increasing burden worldwide. A highly resistant species is Pseudomonas aeruginosa, a nosocomial pathogen that produces a biofilm that enhances its resistance. This project examined the possibility of using bacteriocin, an internal protective toxin produced by some species of bacteria, as a potential treatment for resistant bacteria. In this study, standard broad spectrum antibiotics were used to treat P. aeruginosa to prevent biofilm formation. The biofilm was then analyzed to determine if the biofilm is inhibited or facilitated by each treatment. Optimal concentrations of antibiotics were determined to be effective at a concentration of 0.07mg/mL for …