Citric Acid Confers Broad Antibiotic Tolerance through Alteration of Bacterial Metabolism and Oxidative Stress

Antibiotic tolerance has become an increasingly serious crisis that has seriously threatened global public health. However, little is known about the exogenous factors that can trigger the development of antibiotic tolerance, both in vivo and in vitro. Herein, we found that the addition of citric acid, which is used in many fields, obviously weakened the bactericidal activity of antibiotics against various bacterial pathogens. This mechanistic study shows that citric acid activated the glyoxylate cycle by inhibiting ATP production in bacteria, reduced cell respiration levels, and inhibited the bacterial tricarboxylic acid cycle (TCA cycle). In addition, citric acid reduced the oxidative stress ability of bacteria, which led to an imbalance in the bacterial oxidation-antioxidant system. These effects together induced the bacteria to produce antibiotic tolerance. Surprisingly, the addition of succinic acid and xanthine could reverse the antibiotic tolerance induced by citric acid in vitro and in animal infection models. In conclusion, these findings provide new insights into the potential risks of citric acid usage and the relationship between antibiotic tolerance and bacterial metabolism.

Automated summary

Antibiotic tolerance poses a serious threat to global public health, but the exogenous factors triggering its development are largely unknown. This study demonstrates that citric acid, widely used in various fields, significantly weakens the bactericidal activity of antibiotics against different bacterial pathogens. Mechanistically, citric acid activates the glyoxylate cycle by inhibiting ATP production, reduces cell respiration levels, and inhibits the bacterial tricarboxylic acid cycle. Additionally, citric acid reduces the oxidative stress ability of bacteria, leading to an imbalance in the bacterial oxidation-antioxidant system and subsequent antibiotic tolerance. Surprisingly, the addition of succinic acid and xanthine can reverse the citric acid-induced antibiotic tolerance in vitro and in animal infection models. In conclusion, these findings provide new insights into the potential risks of citric acid usage and the relationship between antibiotic tolerance and bacterial metabolism.