Vector potential of house flies for pathogenic bacteria: the interplay of house fly defenses and microbe temporal and spatial persistence

Since they feed upon and breed in septic substrates, house flies are important in the transmission and dissemination of bacterial disease agents, especially in countries with poor sanitation. Vector potential is enhanced when bacteria are harbored within the fly (e.g., the alimentary canal), where they may have the opportunity to multiply and persist prior to excretion. The survivability of bacteria within the fly gut can be hindered by the house fly’s defenses, including entrapment within the peritrophic matrix and secretion of humoral components such as lysozyme or antimicrobial peptides. Research in my laboratory aims to determine both the spatial and temporal location of bacteria within the house fly alimentary canal, along with the concurrent expression (mRNA and protein) of selected antimicrobial responses. Current investigations include the fate of GFP-expressing Gram positive and Gram negative human pathogens in the house fly. In these studies, microbes were fed to naïve flies and tracked over time by uv microscopy of the entire alimentary canal (crop, midgut, hindgut, rectum). The quantification and recovery of microbes from both flies and their excreta (feces/vomit) also will be presented. Additionally, the accompanying local (alimentary canal) and systemic (fat body) antimicrobial responses will be discussed, including the resulting consequences upon bacterial survivability. The true dissemination and vector potential that flies present for human pathogenic bacteria can be elucidated by examining house fly-microbe interactions both temporally and spatially, and from the perspective of both host and bacterium.