Drosophila melanogaster mitigates gastro-oral infections by stimulating pathogen expulsion

Background Food-borne pathogens, particularly belonging to the Enterobacteriaceae family, are a major cause of gastrointestinal infections in humans. While Drosophila melanogaster has been widely explored to study antimicrobial responses, most studies rely on septic injury or direct injection, routes that bypass the gut. A coordinated set of antimicrobial defenses acts to counteract the invading bacteria, with some variations depending on the entry route into the host. Herein, we tracked the dynamics of Enterobacteriaceae pathogens in Drosophila using a natural infection route. Results Most bacterial species were cleared effectively within 48 hours post-infection (hpi). We did not observe any significant mortality, indicating robust infection control. At 4 hpi, a substantial increase in reactive oxygen species (ROS) production was observed, followed by a decrease at 24 hpi and a resurgence at 48 hpi, suggesting the importance of ROS in bacterial clearance. However, flies lacking the dual oxidase ( Duox ) gene showed unchanged survival rates, suggesting ROS alone is not enough for infection control. We further show that the shedding of bacteria could be attributed to increased TRPA1 expression, a ROS-sensing receptor that triggers intestinal contractions in flies infected with S . Typhimurium and E. cloacae at 4 and 24 hpi. Conclusions Our findings reveal that the host can distinguish and respond to various bacterial species in a well-synchronized, gut-localized, and pathogen-specific manner. This also illustrates the reliability of natural infection route models in unravelling and understanding the complexities of host–pathogen interaction.