PNNL

Abstract

Chronic bacterial infections are difficult to eradicate, though they are caused primarily by drug-susceptible pathogens (1). Antibiotic-tolerant persisters largely account for this paradox. In spite of their significance in recalcitrance of chronic infections, the mechanism of persister formation is poorly understood. We previously reported that a decrease in ATP levels leads to drug tolerance in Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus (2-4). We reasoned that stochastic fluctuation in the expression of TCA cycle enzymes can produce cells with low energy levels. S. aureus knockouts in glutamate dehydrogenase, 2-oxoketoglutarate dehydrogenase, succinyl CoA synthetase, and fumarase have low ATP and exhibit increased tolerance to fluoroquinolone, aminoglycoside, and ?-lactam antibiotics. FACS analysis of TCA genes shows a broad Gaussian distribution in a population, with over three orders of magnitude difference in the levels of expression between individual cells. Sorted cells with low levels of TCA enzyme expression have an increased tolerance to antibiotic treatment. These findings suggest that fluctuation in expression of energy generating components serve as a mechanism of persister formation.