Acid Tolerance of Is Strain-Specific and Might Depend on Stomach Content.

Q fever is a zoonotic disease caused by the obligate intracellular bacterium () . Human infections occur mainly via inhalation, but infections via the oral route have been observed. Gastric acidic conditions (pH 2-4) are the first defense mechanism to limit food-associated infections. In this study, we tested the ability of to survive extremely acidic conditions (pH 2-3) to assess the risk of oral infection in humans. We treated different strains with different pH values and calculated the recovery rate by counting colony-forming units. The analysis of an additional eight strains showed that some strains are acid-resistant, while others are not. Importantly, the presence of pepsin, an endopeptidase and the main digestive enzyme in the gastrointestinal tract, increases the survival rate of . Similarly, the presence of milk might also increase the survival rate. These results suggest that oral infections by are possible and depend on the bacterial strain and the stomach microenvironment. Consequently, the digestive infection route of could play a role in the transmission of the pathogen.