Ascorbate and Antibiotics, at Concentrations Attainable in Urine, Can Inhibit the Growth of Resistant Strains of Escherichia coli Cultured in Synthetic Human Urine

Abstract

There are conflicting reports on the antibacterial activity of ascorbate; all at concentrations much higher than the typical in human plasma, but that can be reached in urine. The effect of 10 mM ascorbate (in itself not inhibitory) along with antibiotics, was tested both in Mueller-Hinton broth (MHb) and in synthetic human urine (SHU), against resistant isolates of Escherichia coli from lower urinary infections. The activity of nitrofurantoin and sulfamethoxazole was higher in SHU than in MHb; minimal inhibitory concentrations (MICs) in SHU with ascorbate were below typical urinary concentrations. For other antibiotics, MICs were the same in MHb vs. SHU, with no effect of ascorbate in MHb; but in SHU with ascorbate, MICs of ciprofloxacin and gentamicin also went below reported urinary concentrations, with a lesser effect with norfloxacin and trimethoprim, and none with ampicillin. The effect of ascorbate was independent of oxygen and not related to the susceptibility of each strain to oxidative stress. Ascorbate oxidizes during incubation in SHU, and bacterial growth partially prevented oxidation. These results suggest that 10 mM ascorbate can enhance the inhibitory activity of antibiotics upon resistant strains in urine. Clinical experimentation with ascorbate–antibiotic combinations against urinary infections caused by resistant bacteria is warranted.

Resveratrol/Selenium Nanocomposite with Antioxidative and Antibacterial Properties

“…Furthermore, the suggested mechanism for their nanocomposite was based on the membrane-damaging activity of selenium nanoparticles. It is important to note that, in addition to selenium, the SeNPs suspension may also contain a residue of protein-BSA and ascorbic acid, both of which could have influenced the observed effects [ 34 , 35 ], but further investigation is necessary to resolve this question. In implant infections, it is usually that biofilm formation is considered as a cause of chronic inflammation [ 3 ].…”

Non-Canonical Aspects of Antibiotics and Antibiotic Resistance

“…Ascorbate diminishes the MIC of several antibiotics towards E. coli in synthetic human urine [ 379 ].…”

“…Antibiotic adjuvants or potentiators -Efflux pump inhibitors, modifying enzymes, membrane permeabilizers [378]. -Ascorbate diminishes the MIC of several antibiotics towards E. coli in synthetic human urine [379].…”