CpxA/R‐Controlled Nitroreductase Expression as Target for Combinatorial Therapy against Uropathogens by Promoting Reactive Oxygen Species Generation

Abstract

The antibiotic resistances emerged in uropathogens lead to accumulative treatment failure and recurrent episodes of urinary tract infection (UTI), necessitating more innovative therapeutics to curb UTI before systematic infection. In the current study, the combination of amikacin and nitrofurantoin is found to synergistically eradicate Gram‐negative uropathogens in vitro and in vivo. The mechanistic analysis demonstrates that the amikacin, as an aminoglycoside, induced bacterial envelope stress by introducing mistranslated proteins, thereby constitutively activating the cpxA/R two‐component system (Cpx signaling). The activation of Cpx signaling stimulates the expression of bacterial major nitroreductases (nfsA/nfsB) through soxS/marA regulons. As a result, the CpxA/R‐dependent nitroreductases overexpression generates considerable quantity of lethal reactive intermediates via nitroreduction and promotes the prodrug activation of nitrofurantoin. As such, these actions together disrupt the bacterial cellular redox balance with excessively‐produced reactive oxygen species (ROS) as “Domino effect”, accelerating the clearance of uropathogens. Although aminoglycosides are used as proof‐of‐principle to elucidate the mechanism, the synergy between nitrofurantoin is generally applicable to other Cpx stimuli. To summarize, this study highlights the potential of aminoglycoside‐nitrofurantoin combination to replenish the arsenal against recurrent Gram‐negative uropathogens and shed light on the Cpx signaling‐controlled nitroreductase as a potential target to manipulate the antibiotic susceptibility.

Tobramycin-resistant small colony variant mutant of Salmonella enterica serovar Typhimurium shows collateral sensitivity to nitrofurantoin

“…The conversion of nitrofurantoin from its prodrug to active form necessitates intracellular processing by bacterial nitroreductases NfsA and NfsB [ 41 ]. As expected, the overexpression of nfsA and nfsB resulted in increased sensitivity to nitrofurantoin (Figure S3 and Table S6).…”

“…In fact, this collateral sensitivity to nitrofurans herein could potentially represent a functional evolutionary trade-off to aminoglycoside resistance. While the precise mechanism of nitrofurans remains to be elusive, their bactericidal activity is believed to primarily involve ROS-mediated oxidative DNA damage [ 41 ]. However, the efficacy of NIT depends on the intracellular conversion of the prodrug to its active form by bacterial nitroreductases NfsA/B [ 55 , 56 ].…”