Pathogenic Microbiology Commons^™

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 …

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 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 …

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 …

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 …

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. …