ABSTRACT
BACKGROUND: SOS response suppression (by RecA inactivation) has been postulated as a therapeutic strategy for potentiating antimicrobials against Enterobacterales. OBJECTIVES: To evaluate the impact of RecA inactivation on the reversion and evolution of quinolone resistance using a collection of Escherichia coli clinical isolates. METHODS: Twenty-three E. coli clinical isolates, including isolates belonging to the high-risk clone ST131, were included. SOS response was suppressed by recA inactivation. Susceptibility to fluoroquinolones was determined by broth microdilution, growth curves and killing curves. Evolution of quinolone resistance was evaluated by mutant frequency and mutant prevention concentration (MPC). RESULTS: RecA inactivation resulted in 2-16-fold reductions in fluoroquinolone MICs and modified EUCAST clinical category for several isolates, including ST131 clone isolates. Growth curves and time-kill curves showed a clear disadvantage (up to 10 log10 cfu/mL after 24 h) for survival in strains with an inactivated SOS system. For recA-deficient mutants, MPC values decreased 4-8-fold, with values below the maximum serum concentration of ciprofloxacin. RecA inactivation led to a decrease in mutant frequency (≥103-fold) compared with isolates with unmodified SOS responses at ciprofloxacin concentrations of 4×MIC and 1 mg/L. These effects were also observed in ST131 clone isolates. CONCLUSIONS: While RecA inactivation does not reverse existing resistance, it is a promising strategy for increasing the effectiveness of fluoroquinolones against susceptible clinical isolates, including high-risk clone isolates.
Subject(s)
Escherichia coli , Quinolones , Anti-Bacterial Agents/pharmacology , Drug Resistance, Bacterial , Escherichia coli/genetics , Fluoroquinolones/pharmacology , Microbial Sensitivity Tests , Quinolones/pharmacologyABSTRACT
Regardless of their targets and modes of action, subinhibitory concentrations of antibiotics can have an impact on cell physiology and trigger a large variety of cellular responses in different bacterial species. Subinhibitory concentrations of ß-lactam antibiotics cause reactive oxygen species production and induce PolIV-dependent mutagenesis in Escherichia coli. Here we show that subinhibitory concentrations of ß-lactam antibiotics induce the RpoS regulon. RpoS-regulon induction is required for PolIV-dependent mutagenesis because it diminishes the control of DNA-replication fidelity by depleting MutS in E. coli, Vibrio cholerae and Pseudomonas aeruginosa. We also show that in E. coli, the reduction in mismatch-repair activity is mediated by SdsR, the RpoS-controlled small RNA. In summary, we show that mutagenesis induced by subinhibitory concentrations of antibiotics is a genetically controlled process. Because this mutagenesis can generate mutations conferring antibiotic resistance, it should be taken into consideration for the development of more efficient antimicrobial therapeutic strategies.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Bacterial Proteins/physiology , DNA Replication/drug effects , Mutagenesis , Sigma Factor/physiology , beta-Lactams/pharmacology , Bacteria/genetics , DNA Replication/physiology , Escherichia coli/drug effects , Escherichia coli/genetics , Escherichia coli/metabolism , Pseudomonas aeruginosa/drug effects , Pseudomonas aeruginosa/genetics , Pseudomonas aeruginosa/metabolism , Reactive Oxygen Species/metabolism , Vibrio cholerae/drug effects , Vibrio cholerae/genetics , Vibrio cholerae/metabolismABSTRACT
En esta obra se analizan los fundamentos de los aspectos nutricionales, dietologicos y psicologicos de la alimentacion del nino. La desnutricion abarca un capitulo importante, destacandose con perfiles originales un trabajo de investigacion clinica sobre la mala absorcion intestinal de los carbohidratos en los distintos tipos de desnutricion cronica
