Document Type
Dissertation
Date of Award
2025
Degree Name
Doctor of Philosophy (PhD)
Department
Basic Biomedical Science
First Advisor
Jose Pietri
Abstract
The following investigates the role of the German cockroach (Blattella germanica) as a vector of the bacterium Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium). As such, this work examines various host-pathogen-microbiome interactions that define the vectorial capacity of the German cockroach for Salmonella. To date, the majority of literature focuses on the general association of the German cockroach with various human pathogens, claiming any dissemination to be carried out via passive mechanical transmission. This project recognizes those claims, while expanding to include the possibility of biological transmission, involving active and complex host-pathogen interactions, including mechanisms like replication within the host. Therefore, various experiments were conducted to test for phenomena such as insect gut colonization, host immune response stimulation, systemic spread of bacteria throughout the host, and the microbiota’s effects on infection susceptibility, both direct and indirect. The observed results serve to shift the current dogma of solely mechanical transmission of Salmonella Typhimurium by the German cockroach. Numerous biological transmission elements were discovered, including: replication of Salmonella within the cockroach, formation of unique bacterial aggregates within the gut, specific stimulation of host antimicrobial peptides in response to secreted virulence factors, sporadic hyper-infected hemocytes, and significant influences of the microbiota on infection outcome including effects from microbiome-induced gut melanin deposits and contributions from low-abundance minority microbiota constituents. Overall, these results describe a dramatically different story of Salmonella Typhimurium’s relationship with the German cockroach, one that involves nuanced interactions at the host-pathogen-microbiome scale demanding increased respect in the public health sector as well as continued research to further characterize this insect’s potential to spread Salmonella and other enteric pathogens.
Subject Categories
Biology
Keywords
German cockroach (Blattella germanic) and bacterium Salmonella
Number of Pages
135
Publisher
University of South Dakota
Recommended Citation
Turner, Matthew, "BLATTELLA GERMANICA AS A VECTOR OF SALMONELLA TYPHIMURIUM" (2025). Dissertations and Theses. 338.
https://red.library.usd.edu/diss-thesis/338