Pathogenic Microbiology Commons^™

The Group A Streptococci Bacteriocins Facilitate A Competitive Advantage During Nasopharyngeal Infection, Lana Estafanos

Electronic Thesis and Dissertation Repository

Pathogenic streptococci have evolved specific systems to eliminate bacterial competitors within their biological niche. In microbial environments, niche competition is often driven by the production of short antimicrobial peptides called bacteriocins; this provides a mechanism by which Streptococcus pyogenes may compete for ecological stability and establish infection. Recent findings from our laboratory have identified two novel Class IIb bacteriocin systems – Streptococcus pyogenes bacteriocin (Spb) JK and MN in the M18 serotype S. pyogenes strain MGAS8232 – that may contribute to nasopharyngeal infection. Here, we show that galactose and CO₂ are distinct regulatory cues which induce antimicrobial activity. Under …

The Surreptitious Survival Of The Emerging Pathogen Staphylococcus Lugdunensis In Macrophages Enhances S. Aureus Infection, David Watson

Electronic Thesis and Dissertation Repository

Staphylococcus lugdunensis is an opportunistic pathogen that can cause invasive infections suggesting an ability to circumvent host immunity. S. lugdunensis was shown to resist killing and persist within macrophages and acetylation of its peptidoglycan is important for this survival. This was consistent in vivo, as S. lugdunensis resides inside Kupffer cells for at least 16 hours post-infection in mice. Despite its capability for survival, S. lugdunensis is unable to replicate within phagolysosomes. Inhibiting phagolysosomal effectors allows S. lugdunensis to initiate replication, after which the bacteria escape phagosomal containment. Moreover, intracellular S. lugdunensis augments the growth S. aureus during co-infection. Eight …

Iron And Copper Homeostasis In Staphylococcus Aureus, Holly A. Laakso

Electronic Thesis and Dissertation Repository

All microorganisms require transition metals for key metabolic processes, thus during infection microbial access to essential metals is tightly regulated by the host in a process termed nutritional immunity. Iron acquisition is critical to the pathogenesis of the formidable human pathogen, Staphylococcus aureus, which utilizes heme-uptake systems and two high-affinity iron-scavenging siderophores, staphyloferrin A (SA) and staphyloferrin B (SB) for iron acquisition. In this study, I identify sbnI as encoding a transcription factor required for expression of genes in the sbn operon, the biosynthetic operon for SB synthesis. I also show that SbnI is a novel hemoprotein, where binding …

The Effect Of Diet On Midgut And Resulting Changes In Infectiousness Of Acmnpv Baculovirus In Trichoplusia Ni, Elizabeth Chen

Electronic Thesis and Dissertation Repository

The cabbage looper, Trichoplusia ni, a global generalist lepidopteran pest, has developed resistance to many synthetic and biological insecticides, requiring effective and environmentally acceptable alternatives. One possibility is the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). This baculovirus is highly infectious for T. ni, with potential as a biocontrol agent, however, its effectiveness is strongly influenced by dietary context. In this study, microscopy and transcriptomics were used to examine how the efficacy of this virus was affected when T. ni larvae were raised on different diets. Larvae raised on potato host plants had lower chitinase and chitin deacetylase transcript levels …

Examination Of Bcaa Transport And Synthesis In Staphylococcus Aureus, Julienne Kaiser

Electronic Thesis and Dissertation Repository

Staphylococcus aureus is a human pathogen capable of causing infections that range from mild skin and soft tissue infections to severe infections of the bone, muscle, heart, and lung. To survive and thrive in such diverse host environments, S. aureus must maintain sufficient levels of metabolites and cofactors to support virulence determinant production and replication. The branched-chain amino acids (BCAAs; Ile, Leu, Val) represent an important group of nutrients for S. aureus metabolism, as they are required for protein synthesis and synthesis of membrane branched-chain fatty acids (BCFAs), which are important for S. aureus environmental adaptation. Moreover, the BCAAs are …

Development And Performance Evaluation Of An Antibody-Based Technology For Detection Of E. Coli O157 In Meat Samples And Its Potential Evolution Using Antibody Engineering, Yadira Tejeda Saldaña

Electronic Thesis and Dissertation Repository

Escherichia coli O157 is a persistent pathogen linked to food and waterborne infectious outbreaks with severe health consequences such as hemorrhagic colitis and hemolyticuremic syndrome (HUS). Because it is considered one of the major pathogens that contributes to the global burden of foodborne disease, its early detection within the food chain is an important milestone towards reducing foodborne diseases and economic losses due to contaminated food. Herein, the development and validation of a lateral flow immunoassay (LFIA) point-of-care (POC) device is described. Application of the LFIA test kit was focused on detection of E. coli O157 in raw meat products …

Iron Acquisition Strategies Employed By Staphylococcus Lugdunensis, Jeremy R. Brozyna

Electronic Thesis and Dissertation Repository

Iron is crucial for many cellular processes including DNA synthesis and respiration. The majority of iron in mammals is in heme within hemoproteins, inside cells, or transported through circulation by the glycoprotein transferrin, which constitutes the greatest iron source in serum. Limiting iron availability is an important facet of nutritional immunity to help prevent infection.

Staphylococcus lugdunensis is a human skin commensal and opportunistic pathogen capable of causing a variety of infections, including particularly aggressive endocarditis. It is an emerging pathogen with elevated virulence compared to other species of coagulase-negative staphylococci. The versatility of S. lugdunensis to infect multiple niches …

At The Interface Of Glycolipids And Glycoproteins In The Two Gastro-Intestinal Pathogens Campylobacter Jejuni And Helicobacter Pylori, Najwa Zebian

Electronic Thesis and Dissertation Repository

Campylobacter jejuni and Helicobacter pylori are phylogenetically related human gastro-intestinal pathogens. C. jejuni colonizes the intestine and is the leading cause of bacterial gastroenteritis worldwide. H. pylori colonizes the stomach of half the world’s population, causing gastritis, gastric ulcers and gastric cancer. Both pathogens express glycoproteins and glycolipids (capsule, lipooligosaccharide or lipopolysaccharide (LPS)) that are important in pathogenesis. Sugar units from capsule or LPS can modify proteins in several bacteria. We reasoned that this may occur in C. jejuni and H. pylori as means to diversify their surface glycosylation and aid in colonization, immune evasion and virulence.

The putative sugar …

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, …

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 …

The Role Of Superantigens During Staphylococcus Aureus Nasal Colonization And Infection, Stacey Xu

Electronic Thesis and Dissertation Repository

Superantigens (SAgs) are potent toxins produced by bacteria such as Staphylococcus aureus that function to overactivate T cells resulting in massive cytokine production and immune activation. Despite decades of research on the structure and function of these proteins, as well as their role in severe diseases such as toxic shock syndrome, the question as to why strains of S. aureus produce SAgs and the role that they play in the life cycle of these bacteria remains unanswered. The contribution of SAgs towards pathogenicity and bacterial survival in vivo were assessed using isogenic SAg deletion knockouts in conjunction with SAg-sensitive humanized …

Sub-Inhibitory Antibiotics Enhance Virulence, Persistence, And Pathogenesis Of Uropathogens, Lee W. Goneau

Electronic Thesis and Dissertation Repository

In addition to their bactericidal effects, antibiotics are potent signal mediators at sub-inhibitory levels in the environment. The ability to modulate community structure in this niche raises concerns over their capacity to influence pathogenesis in patients during antibiotic therapy. This concept forms the basis of this thesis, and is explored using models of prophylactic therapy for recurrent urinary tract infection (UTI) management.

Sub-inhibitory ciprofloxacin, ampicillin, and gentamicin were found to augment virulence in vitro, increasing adherence and urothelial cell invasion in uropathogenic Escherichia coli (UPEC) and Staphylococcus saprophyticus. In addition, biofilm formation was increased, and swarming motility decreased. …

Characterization Of Staphylococcus Aureus Lipase, Vithooshan Vijayakumaran

Electronic Thesis and Dissertation Repository

USA300, a strain of community-associated methicillin resistant Staphylococcus aureus (CA-MRSA), has become prevalent in the community. Colonization of human skin requires mechanisms that allow this bacterium to overcome the innate immune defenses on the skin, including secretion of antimicrobial lipids. Antimicrobial lipids inhibit S. aureus growth and induce the staphylococcal proteolytic cascade, producing aureolysin (Aur) which processes the lipase glycerol ester hydrolase (Geh). Nearly all S. aureus strains secrete Geh, yet little information exists concerning its function. Using purified Aur and Geh we confirm that aureolysin processes proGeh to Geh. We then confirmed that geh was required for lipase activity …

Staphylococcus Aureus Response To Long Chain Antimicrobial Fatty Acids, Benjamin Arsic

Electronic Thesis and Dissertation Repository

Staphylococcus aureus is a common pathogen that has the ability to infect virtually every tissue and organ system of the body. Despite its propensity to cause invasive infection, S. aureus is also a commensal organism, asymptomatically colonizing ~25% of the population. Much research has gone into resolving this paradox, focusing on both human and bacterial factors that may contribute to colonization. Antimicrobial fatty acids present on the skin and in the nasal mucosa are important components of the innate immune system, and thus we undertook to further understand how S. aureus responds to these fatty acids, and how this response …