Environmental acquisition of ST398 Staphylococcus aureus by patients with chronic respiratory disease

Abstract Staphylococcus aureus is a major human pathogen and a leading bacterial cause of death worldwide. Some S. aureus lineages, including ST398, commonly infect livestock but are rare in humans. These livestock- associated bacteria commonly acquire tetracycline resistance from the use of antibiotics for animal production. Recently, we discovered that over 5% of patients with cystic fibrosis (CF) are infected with ST398 S. aureus, suggesting that this livestock-associated lineage has jumped into the human population. It is not clear how these patients developed ST398 infections. The goal of this research project is to determine whether these ST398 infections persist in people with CF and to identify potential environmental sources such as food or water are the sources of these infections. We hypothesize that ST398 infections persist for 3 years in half of patients who become infected. We also hypothesize that ST398 infections are acquired indirectly from livestock through either contaminated water supply or from the food supply chain. We will test these hypotheses by prospectively collecting both clinical and environmental isolates of S. aureus and genome sequencing isolates that are tetracycline resistant, a common marker of this lineage. We will use phylogenetic and geospatial analysis to rigorously examine the relationship between strains of ST398 that infect patients with CF and that are found in water collected around the state of Iowa, bioaerosols collected near animal production facilities, or meat collected from local grocery suppliers.