Diet has minimal effect on Salmonella Typhimurium infection in the gut of a cockroach vector despite altering the...

The German cockroach, Blattella germanica, can harbor and transmit enteric human pathogens, including Salmonella enterica serovar Typhimurium. German cockroaches are omnivores that subsist on highly varied diets in the field, in contrast to most arthropod vectors. Diet plays an important role in shaping the gut microenvironment across a range of animals, which can in turn affect numerous aspects of physiology, including the ability to resist infection. Yet, the impact of diet on the ability of cockroaches to maintain and transmit pathogens had not been investigated previously. Here, we tested the hypothesis that dietary differences among otherwise identical populations of B. germanica could lead to differences in vector competence for S. Typhimurium. Cockroaches were maintained on three defined formulated diets with distinct macronutrient profiles for 10 days. Food consumption was monitored during this period, and the gut microbiome was profiled by 16S rRNA amplicon sequencing. The cockroaches were then orally infected with S. Typhimurium, and pathogen loads in the gut and excreta were quantified. Cockroaches equally consumed formulated high-protein, high-fat, and high-carbohydrate diets in no-choice assays. Furthermore, as expected, some significant differences in microbiome composition and diversity were observed between groups of cockroaches maintained on different diets. However, despite the effects on the microbiome, no significant diet-dependent differences in the load of S. Typhimurium maintained in the gut or shed in the excreta were observed. Although the results provide evidence that the dietary macronutrient profile is not a major contributor to vector competence, the possibility that other natural diets could influence pathogen infection and transmission dynamics is not ruled out by this study.

German cockroaches are one of the most common structural pests worldwide, while Salmonella enterica serovar Typhimurium is an emerging human pathogen accounting for a significant portion of the global burden of enteric disease. Understanding the factors that contribute to the ability of cockroaches to transmit pathogens is important for infection prevention, but these remain almost entirely unknown. Here, we provide new insight into the variables involved in the vector competence of cockroaches.