Document Type
Thesis
Date of Award
2025
Degree Name
Master of Science (MS)
Department
Basic Biomedical Science
First Advisor
Jose Pietri
Abstract
The German cockroach (Blattella germanica) is a common urban pest that lives ubiquitously in human structures around the world. German cockroaches are a severe public health threat as they are known carriers and vectors of human pathogens including Salmonella enterica, Escherichia coli, Shigella spp, and more. German cockroach infestations have been associated with Salmonellosis outbreaks. While mechanical transmission by the German cockroach vector is well known, new research suggests that more nuanced biological transmission has a role in maintaining and transmitting Salmonella enterica serovar Typhimurium (S. Typhimurium). Despite this recent finding, many biological variables influencing vector-borne transmission of S. Typhimurium by cockroaches are unexplored or understudied. In order to create a more complete understanding of the vector-pathogen relationship between B. germanica and S. Typhimurium, we designed and executed experiments to investigate the influences of S. Typhimurium aggregate formation, the cockroach microbiota, and insecticide exposure on infection of B. germanica. Our work shows that S. Typhimurium, unlike E. coli, can form biofilm-like aggregates in the cockroach gut that are dependent on FimA gene expression. The phenomenon of aggregate formation increases the ability of S. Typhimurium to colonize the cockroach gut. The cockroach microbiota also influences cockroach susceptibility to S. Typhimurium. We demonstrate that in vitro, commensal bacteria do not limit Salmonella colonization of the cockroach gut by competition and that total commensal microbial density does not affect Salmonella colonization of the cockroach gut. Instead, a few specific minority commensal taxa are associated with susceptibility to Salmonella infection. Within this same study, it was also shown that the microbiome functions to prime the cockroach immune system against infection with S. Typhimurium by increasing antimicrobial peptide expression. Lastly, we show that exposure to the insecticide indoxacarb significantly increases Salmonella infection in certain cockroach strains. These investigations reveal novel factors that affect the vector competence of cockroaches for S. Typhimurium.
Subject Categories
Microbiology
Keywords
Cockroach Insecticide Microbiome Salmonella Vector
Number of Pages
78
Publisher
University of South Dakota
Recommended Citation
Van Hulzen, Landen Sean, "INVESTIGATION OF MULTIPLE FACTORS INFLUENCING THE VECTOR-BORNE TRANSMISSION OF SALMONELLA TYPHIMURIUM VIA BLATTELLA GERMANICA" (2025). Dissertations and Theses. 330.
https://red.library.usd.edu/diss-thesis/330