Selective Target Inactivation Rather than Global Metabolic Dormancy Causes Antibiotic Tolerance in Uropathogens

Abstract

Persister cells represent a multidrug-tolerant (MDT), physiologically distinct subpopulation of bacteria. The ability of these organisms to survive lethal antibiotic doses raises concern over their potential role in chronic disease, such as recurrent urinary tract infection (RUTI). Persistence is believed to be conveyed through global metabolic dormancy, which yields organisms unresponsive to external stimuli. However, recent studies have contested this stance. Here, various antibiotics that target different cellular processes were used to dissect the activity of transcription, translation, and peptidoglycan turnover in persister cells. Differential susceptibility patterns were found in type I and type II persisters, and responses differed between Staphylococcus saprophyticus and Escherichia coli uropathogens. Further, SOS-deficient strains were sensitized to ciprofloxacin, suggesting DNA gyrase activity in persisters and indicating the importance of active DNA repair systems for ciprofloxacin tolerance. These results indicate that global dormancy per se cannot sufficiently account for antibiotic tolerance. Rather, the activity of individual cellular processes dictates multidrug tolerance in an antibiotic-specific fashion. Furthermore, the susceptibility patterns of persisters depended on their mechanisms of onset, with subinhibitory antibiotic pretreatments selectively shutting down cognate targets and increasing the persister fraction against the same agent. Interestingly, antibiotics targeting transcription and translation enhanced persistence against multiple agents indirectly related to these processes. Conducting these assays with uropathogenic E. coli isolated from RUTI patients revealed an enriched persister fraction compared to organisms cleared with standard antibiotic therapy. This finding suggests that persister traits are either selected for during prolonged antibiotic treatment or initially contribute to therapy failure.

Subinhibitory Concentrations of Bacteriostatic Antibiotics Induce relA -Dependent and relA -Independent Tolerance to β-Lactams

“…The dramatic difference in ampicillin and norfloxacin killing results (compare Fig. 5 and 6) supports the assertion that elevated levels of (p)ppGpp induce antibiotic tolerance via antibiotic-specific pathways rather than protection from antibiotics in general (57, 77–80). Although the role of (p)ppGpp in ampicillin tolerance is well established, (p)ppGpp's role in protection from gyrase inhibitors such as norfloxacin is controversial: although some studies, similar to our own results, report an absence of specific protection (81), other studies observed prominent effects (4, 82).…”

In Vitro Emergence of High Persistence upon Periodic Aminoglycoside Challenge in the ESKAPE Pathogens

“…Studies of longitudinal isolates from long-term chronic infections have also delivered indirect evidence that the evolution of persistence occurs in vivo. In long-term P. aeruginosa lung infections, selection for increased persister levels without an increase in resistance was reported (15), and similar observations were made in uropathogenic E. coli (52) and the fungal pathogen Candida albicans (53). However, no selection for increased persistence in Burkholderia species was seen during prolonged treatment of infected lungs (54).…”

Elucidating the role of (p)ppGpp in mycobacterial persistence against antibiotics

“…Since most antibiotics target processes required for growth and division and consequently cells that are actively growing and dividing, persisters were suggested to be in a dormant or slow‐growing state . While this correlation between growth rate and persistence has been confirmed in several recent studies , it is also becoming evident that just being in a non‐growing state does not impart antibiotic tolerance . Also several studies, mostly using E. coli , have started identifying the key players involved in persistence and have started uncovering the mechanistic details of this process .…”