The vulnerable versatility of Salmonella antibiotic persisters during infection.

Tolerance and persistence are superficially similar phenomena by which bacteria survive bactericidal antibiotics. It is assumed that the same physiology underlies survival of individual tolerant and persistent bacteria. However, by comparing tolerance and persistence during Salmonella Typhimurium infection, we reveal that these two phenomena are underpinned by different bacterial physiologies. Multidrug-tolerant mutant Salmonella enter a near-dormant state protected from immune-mediated genotoxic damages. However, the numerous tolerant cells, optimized for survival, lack the capabilities necessary to initiate infection relapse following antibiotic withdrawal. In contrast, persisters retain an active state. This leaves them vulnerable to accumulation of macrophage-induced dsDNA breaks but concurrently confers the versatility to initiate infection relapse if protected by RecA-mediated DNA repair. Accordingly, recurrent, invasive, non-typhoidal Salmonella clinical isolates display hallmarks of persistence rather than tolerance during antibiotic treatment. Our study highlights the complex trade-off that antibiotic-recalcitrant Salmonella balance to act as a reservoir for infection relapse.