Pathogenic Microbiology Commons^™

Impact Of Temperature And Microbial Infection On The Honey Bee Hemocytes, Michael E. Oeth

Master's Theses

Introduction

Honey bees (Apis mellifera) rely on hemocytes for immunity, wound healing, and hemolymph homeostasis. While 32°C reflects optimal hive conditions, suboptimal temperatures (22°C) and stressors like pathogens (Varroa destructor, bacteria) or pesticides impair hemocyte function. Using clodronate liposomes (CLD) to deplete hemocytes, we assessed how immune suppression interacts with these stressors.

Methods

Newly emerged (5-day-old) and older (15-day-old) bees were assigned to: CLD, control liposomes (LP), PBS, injection wound, or no treatment. Cohorts were exposed to 32°C (optimal) or 22°C (stressful for non-immunosuppressed bees). Fifteen-day-old bees were challenged with Escherichia coli or Staphylococcus aureus. Survival, hemolymph volume, and hemocyte …

Invasion Properties Of Listeria Monocytogenes In Aged Cells, Mina Lane Chasteen Burton

Honors Theses

Listeriosis is a bacterial infection caused by the gram-positive pathogen Listeria monocytogenes. When compared to other foodborne illnesses, listeriosis has a higher death rate due to an increased incidence of complications such as meningitis, hydrocephalus, and sepsis in immunocompromised populations. Elderly individuals experience a condition known as immunosenescence, which is a gradual compromisation of the immune system brought on by natural aging. Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder causing premature aging, which allows HGPS cell lines to be used as models to further research in the field of biogerontology. This study utilizes the F2365 strain of …

An Investigation On The Impact Of Intestinal Oxygen Availability On Survival And Regulation Of Virulence In Listeria Monocytogenes, Damayanti Chakravarty

Dissertations

The deadly foodborne pathogen Listeria monocytogenes is a gram positive facultative anaerobic bacterium. It is the third leading cause of death from food-borne illnesses. Once ingested, it encounters various stressors in the gastrointestinal (GI) tract, including acidic pH, bile, and alterations in oxygen availability. Various studies have been done regarding the pathogen’s survival mechanism against acid and bile. Since the lower parts of the GI tract are anaerobic, it is imperative to investigate how physiologically relevant anaerobic conditions impact L. monocytogenes’s survival. Transcriptomic analysis of L. monocytogenes under conditions mimicking the GI tract was performed. A large number of genes …

An Exploratory Study On The Microbiome Of Northern And Southern Populations Of Ixodes Scapularis Ticks Predicts Changes And Unique Bacterial Interactions, Deepak Kumar, Latoyia P. Downs, Abdulsalam Adegoke, Erika Machtinger, Kelly Oggenfuss, Richard S. Ostfeld, Monica Embers, Shahid Karim

Faculty Publications

The black-legged tick (Ixodes scapularis) is the primary vector of Borrelia burgdorferi, the causative agent of Lyme disease in North America. However, the prevalence of Lyme borreliosis is clustered around the Northern States of the United States of America. This study utilized a metagenomic sequencing approach to compare the microbial communities residing within Ix. scapularis populations from northern and southern geographic locations in the USA. Using a SparCC network construction model, we performed potential interactions between members of the microbial communities from Borrelia burgdorferi–infected tissues of unfed and blood-fed ticks. A significant difference in bacterial composition …

The Role Of The Msaabcr Operon In Cell Wall Integrity And Programmed Cell Death During Biofilm Development, Bibek G C

Dissertations

Staphylococcus aureus is an important human pathogen in both community and health care settings. Biggest challenges with S. aureus as a pathogen is its ability to acquire antibiotic resistance and produce robust biofilms. In this work, we investigated the nature of the cell wall defect in the msaABCR operon mutant in the Mu50 (VISA) and USA300 LAC methicillin-resistant Staphylococcus aureus (MRSA) strains. Results showed that msaABCR-mutant cells had decreased cell wall thickness and cell wall crosslinking in both strains. These defects are most likely due to increased murein hydrolase activity and/or nonspecific processing of murein hydrolases mediated by increased …

The Impact Of Oxygen Availability And Oxidative Stress On Regulation Of Cyclic-Dimeric-Gmp In Listeria Monocytogenes Strain F2365, Anna G. Welch

Honors Theses

Listeria monocytogenes is a gram-positive foodborne pathogen that results in the infectious disease listeriosis. The second messenger molecule cyclic-dimeric-GMP has been found to be responsible for the regulation of expression of many of its virulence factors with diguanylate cyclases and phosphodiesterases regulating the intracellular concentration of cyclic-di-GMP through synthesis and degradation, respectively. This study investigated the possibility that the availability of oxygen is the environmental signal crucial to the regulation of these enzymes. Prior research in our laboratory has demonstrated that the intracellular concentration of cyclic-di-GMP is elevated when exposed to anaerobic conditions. Due to this, it was hypothesized that …

Study Of The Role Of The Msaabcr Operon In Tricarboxylic Acid Cycle Activity And Persister Cell Formation In Staphylococcus Aureus, Karsen Motter

Honors Theses

Staphylococcus aureus is an important human pathogen that causes wide arrays of infections ranging from minor skin infections to lethal systemic conditions such as infective endocarditis, osteomyelitis, sepsis and pneumonia. These systemic diseases are often difficult to treat due to the presence of persister cells. Persister cells are a phenotypic variant of the bacterial population that exhibit extreme and transient antibiotic tolerance accompanied by a transient halt in growth. Upon cessation of antibiotic treatment, however, persisters resume growth which results in recurrence of infections. This characteristic of persister cells therefore displays high clinical significance. In this study, we show the …

Interregulation Between Msaabcr Operon And Ccpe To Determine Staphylococcal Metabolism And Virulence, Erin R. Cox

Honors Theses

Staphylococcus aureus is a complex human pathogen that causes problems in both healthcare and community settings. Staphylococcus aureus is a gram-positive, sphere shaped bacterium that usually colonizes in the nasal cavity of healthy individuals. Staphylococcus aureus infections are a growing health concern due to its ability to produce virulence factors, such as pigmentation, protease production, and capsule formation. Two regulators in S. aureus virulence factors are msaABCR, which is a newly characterized operon, and ccpE. In order to determine the interaction between these two regulators in regulating virulence and metabolism in S. aureus, ccpE and ccpE/ …

Phenotypic Characterizations Of Msaabcr Operon Deletion In Staphylococcus Epidermidis Rp62a, Raelyn Williams

Honors Theses

Staphylococcus epidermidis is a human pathogen that is increasingly known for its role in hospital infections associated with implantable medical devices. Antibiotic resistance has become a concerning issue for these infections as this bacteria have various virulence traits that help to evade immune response and antibiotic treatment. Currently, the most effective way to treat S. epidermidis infection is removal of the implant and long-term antibiotic treatment. S. epidermidis causes infection by expressing several protein factors that induce biofilm formation, the bacteria’s primary virulence mechanism. The purpose of this study was to perform the phenotypic characterizations of the msaABCR operon in …

Regulation Of Weak Acid-Dependent Cell Death By The Msaabcr Operon During Biofilm Formation Of Staphylococcus Aureus, Sarah-Elizabeth M. Polley

Honors Theses

Staphylococcus aureus is a dangerous human pathogen and a leading cause of both nosocomial and community-associated infections. Infection by S. aureus is a growing health concern due to the emergence of antibiotic resistance and the capability to form robust biofilms. Major constituents of the biofilm extracellular matrix are demonstrated to be released via controlled autolysis of a subpopulation of the biofilm. As indicated in past studies, the programmed cell death (PCD) of S. aureus grown in a biofilm microenvironment is potentiated by the buildup of acetate, a byproduct of glucose metabolism, which causes cytoplasmic acidification. Furthermore, it has been shown …

Listeria Monocytogenes Response To Anaerobic Environments, Brandy N. Roberts, Damayanti Chakravarty, J.C. Gardner Iii, Steven C. Ricke, Janet R. Donaldson

Faculty Publications

Listeria monocytogenes is a Gram-positive facultative anaerobic bacterium that is responsible for the disease, listeriosis. It is particularly lethal in pregnant women, the fetus, the elderly and the immunocompromised. The pathogen survives and replicates over a wide range of temperatures (4 to 42 °C), pH, salt and oxygen concentrations. Because it can withstand various environments, L. monocytogenes is a major concern in food processing industries, especially in dairy products and ready-to-eat fruits, vegetables and deli meats. The environment in which the pathogen is exposed can influence the expression of virulence genes. For instance, studies have shown that variations in oxygen …

The Histoplasma Capsulatum Ddr48 Gene Is Required For Survival Within Macrophages And Resistance To Oxidative Stress And Antifungal Drugs, Logan Blancett

Dissertations

Histoplasma capsulatum(Hc)is a systemic, dimorphic fungal pathogen that affects upwards of 500,000 individuals in the United States annually. Hc grows as a multicellular mold at environmental temperatures; whereas, upon inhalation into a human or other mammalian host, it transforms into a unicellular, pathogenic yeast. The research presented in this dissertation is focused on characterizing the DNA damage-responsive gene HcDDR48. HcDDR48was originally isolated via a subtractive DNA library enriched for transcripts enriched in the mold-phase of Hcgrowth. Upon further analysis we found that HcDDR48is not just expressed in the mold morphotype, but both growth programs …

The Antimicrobial Activity And Cellular Targets Of Plant Derived Aldehydes And Degradable Pro-Antimicrobial Networks In Pseudomonas Aeruginosa, Yetunde Adewunmi

Dissertations

Essential oils (EOs) are plant-derived products that have been long exploited for their antimicrobial activities in medicine, agriculture, and food preservation. EOs represent a promising alternative to conventional antibiotics due to the broad-range antimicrobial activity, low toxicity to human commensal bacteria, and the capacity to kill microorganisms without promoting resistance. Despite the progress in the understanding of the biological activity of EOs, many aspects of their mode of action remain inconclusive. The overarching aim of this work was to address these gaps by studying molecular interactions between antimicrobial plant aldehydes and the opportunistic human pathogen Pseudomonas aeruginosa. We initiated …

The Thiol Specific Antioxidant (Tsa1) Gene Is Required For Survival In Macrophages And Oxidative Stress Resistance In Histoplasma Capsulatum, Lauren Kennedy

Master's Theses

Histoplasma capsulatum(Hc) is a pathogenic fungus that causes one of the most common invasive fungal respiratory diseases, Histoplasmosis. Histoplasmaundergoes a dimorphic shift from mold to yeast which is crucial to pathogenesis of the organism.

The thiol specific antioxidant gene, Tsa1,is strongly upregulated in the yeast (pathogenic) morphotype. This data led to the hypothesis that this gene plays a role in protecting Hcfrom host mediated oxidative attack. To characterize Tsa1 function, a knockdown strain (tsa1-RNAi) was created by RNAi gene silencing. Expression of Tsa1in the tsa1-RNAistrain was reduced to 10% that …

Current Understanding Of West Nile Virus Clinical Manifestations, Immune Responses, Neuroinvasion, And Immunotherapeutic Implications, Fengwei Bai, E. Ashley Thompson, Parminder J.S. Vig, A. Arturo Leis

Faculty Publications

West Nile virus (WNV) is the most common mosquito-borne virus in North America. WNV-associated neuroinvasive disease affects all ages, although elderly and immunocompromised individuals are particularly at risk. WNV neuroinvasive disease has killed over 2300 Americans since WNV entered into the United States in the New York City outbreak of 1999. Despite 20 years of intensive laboratory and clinical research, there are still no approved vaccines or antivirals available for human use. However, rapid progress has been made in both understanding the pathogenesis of WNV and treatment in clinical practices. This review summarizes our current understanding of WNV infection in …

Parasitic Microbiome Project: Grand Challenges, Nolwenn M. Dheilly, Joaquín Martínez Martínez, Karyna Rosario, Paul J. Brindley, Raina N. Fichorava, Jonathan Z. Kaye, Kevin D. Kohl, Laura J. Knoll, Julius Lukeš, Susan L. Perkins, Robert Poulin, Lynn Schriml, Luke R. Thompson

Faculty Publications

No abstract provided.

Stress Response Mechanisms Of Listeria Monocytogenes, Oindrila Paul

Dissertations

Listeria monocytogenes is a Gram-positive, facultative intracellular food-borne pathogen that causes the disease listeriosis. In order to establish an infection, L. monocytogenes must survive multiple stressors encountered within the gastrointestinal tract, including alterations in pH, bile, salt, and oxygen availability. This dissertation focused on understanding the stress response of L. monocytogenes to bile. Bile acts as a bactericidal agent by disrupting the membrane integrity and causing instability to macromolecules like DNA. Thus, a bacterium must be able to maintain its membrane architecture, composition and integrity.

Often times, bacteria will modulate their fatty acid composition in the membrane to cope with …

Msab And Cody Interact To Regulate Staphylococcus Aureus Capsule In A Nutrient-Dependent Manner, Justin Batte, Gyan S. Sahukhal, Mohamed O. Elasri

Faculty Publications

Staphylococcus aureus has a complex regulatory network for controlling the production of capsule polysaccharide. In S. aureus, capsule production is controlled by several regulators in response to various environmental stimuli. Previously, we described MsaB as a new regulator that specifically binds to the cap promoter in a growth-phase or nutrient-dependent manner. In addition to MsaB, several other regulators have also been shown to bind the same region. In this study, we examined the interactions between MsaB and other nutrient-sensing regulators (CodY and CcpE) with respect to binding to the cap promoter in a nutrient-dependent manner. We observed that msaABCR …

The Characterization Of The Transcription Factor Msab And Its Role In Staphylococcal Virulence, Justin Batte

Dissertations

Staphylococcus aureus is a common human pathogen that is responsible for a wide range of infections, ranging from relative minor skin infections to life-threatening disease such as bacteremia, septicemia, and endocarditis. S. aureus possesses many different virulent factors that aid in its ability to cause this wide array of infections. One major virulence factor includes the production of capsular polysaccharide (CP). The production of CP plays a major role in the virulence response during infection specifically by providing S. aureus an antiphagocytic mechanism that allows the pathogen to evade phagocytosis during an infection. S. aureus has developed complex genetic regulatory …

The Regulatory Relationship Of Transcriptional Regulators Msab And Cody In Capsule Production In Staphylococcus Aureus, Brittany L. Trunell

Honors Theses

There are many transcriptional regulators found in pathogenic Staphylococcus aureus. Many of these regulators are essential for the organism’s ability to switch from commensal form to the virulent pathogenic form. One of these main regulators is CodY. This regulator has been shown to be responsive to nutrient availability during phases of growth. Additionally, we have recently found that MsaB, the only protein coding ORF of the msaABCR operon, is a putative co-regulator of capsule along with CodY. To explore these regulator interactions, we produced mutations of codY and msaABCR individually and a double mutation of msaABCR/ codY. We have observed …

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. …

Study Of The Function Of The Mold Specific Gene Ms95 In Dna Repair In The Pathogenic, Dimorphic Fungus Histoplasma Capsulatum, Erin M. Smith

Honors Theses

Histoplasma capsulatum (Hc) is a dimorphic fungus that is the etiologic agent of the respiratory infection Histoplasmosis that is mediated by a shift from the mold phase to the pathogenic yeast phase. Genes have been identified that are specific to the mold or yeast phase in order to study the molecular biology of this shift. MS95 was identified in a subtractive cDNA library that was enriched for mold-specific genes, and has been found to be homologous to the DNA damage-responsive gene DDR48, which functions in DNA repair in Saccharomyces cerevisiae. In order to elucidate the function of MS95, a …

Molecular Detection Of Tick-Borne Pathogens Associated With Ixodid Tick Species Infesting Migratory Songbirds And Ruminants, Nabanita Mukherjee

Master's Theses

Ticks are hematophagous arthropods and capable of inoculating various infectious agents to their vertebrate hosts. Ticks attached to birds and ruminants are capable of carrying tick-transmitted microorganisms. In our study, the prevalence of tick-borne pathogens was examined in ticks infesting migratory songbirds and Pakistani ruminants. During spring migration seasons, ticks were removed from northward-migrating songbirds in Louisiana and identified as Amblyomma Jongirostre, Amblyomma nodosum, Amb/yomma ca/caratum, Amblyomma maculatum, and Haemaphysalis species, all are considered as Neotropical ticks. Ticks removed from ruminants were identified as Hya/omma anatolicum, Hyalomma dromedarii, Rhipicephalus microplus, and Rhipicephalus sanguineus. A total of 112 and 72 bacterial …