Antibacterial effect of vitamin C against uropathogenic E. coli in vitro and in vivo.

BACKGROUND: Resistance to antibiotics has increased steadily over time, thus there is a pressing need for safer alternatives to antibiotics. Current study aims to evaluate the influence of vitamin C as an antibacterial and anti-biofilm agent against uropathogenic E. coli (UPEC) strains. The expression of beta-lactamases and biofilm encoding genes among E. coli isolates before and after treating the isolates with sub MIC of vitamin C was analyzed by Real-time PCR. The in vivo assessment of the antibacterial and anti-biofilm effects of vitamin C against uropathogenic E. coli strains was done using a urinary tract infection (UTI) rat model. RESULTS: The effective concentration of vitamin C that could inhibit the growth of most study isolates (70%) was 1.25 mg/ml. Vitamin C showed a synergistic effect with most of the studied antibiotics; no antagonistic effect was detected at all. Vitamin C showed an excellent anti-biofilm effect against studied isolates, where 43 biofilm-producing isolates were converted to non-biofilm at a concentration of 0.312 mg/ml. The expression levels of most studied genes were down-regulated after treatment of E. coli isolates with vitamin C. In vivo assessment of vitamin C in treating UTIs showed that vitamin C has a rapid curative effect as the comparable antibiotic. Administration of both vitamin C and nitrofurantoin at a lower dose for treatment of UTI in rats had a better effect. CONCLUSION: Vitamin C as an antibacterial and anti-biofilm agent either alone or in combination with antibiotics could markedly improve UTI in experimental rats.

Assessment of Antibacterial and Anti-biofilm Effects of Vitamin C Against Pseudomonas aeruginosa Clinical Isolates.

There is a persistent need to look for alternative therapeutic modalities to help control the pandemic of antimicrobial resistance. Assessment of antibacterial and anti-biofilm effects of vitamin C (ascorbic acid) was the aim of the current study. The micro-dilution method determined the minimal inhibitory concentration (MIC) of ascorbic acid or antibiotics alone and in combinations against Pseudomonas aeruginosa (P. aeruginosa) clinical isolates. The micro-titer plate method monitored the effect of ascorbic acid on the biofilm-producing isolates of P. aeruginosa. The effect of ascorbic acid on the differential expression of different antibiotic-resistant genes and biofilm encoding genes of P. aeruginosa isolates were also tested using real-time polymerase chain reaction (PCR). For in vivo assessment of the antibacterial effects of ascorbic acid alone or combined with an antibiotic, rats were infected with P. aeruginosa clinical isolate followed by different treatment regimens. MICs of ascorbic acid among P. aeruginosa isolates were in the range of 156.2-1,250 µg/ml, while MIC50 and MIC90 were 312.5 and 625 µg/ml, respectively. At sub-inhibitory concentrations (19.5-312.5 µg/ml), ascorbic acid had 100% biofilm inhibitory effect. Furthermore, ascorbic acid-treated bacteria showed downregulation of genes underpinning biofilm formation and antibiotic resistance. In vivo assessment of vitamin C and ceftazidime in rats showed that administration of both at a lower dose for treatment of pseudomonas infection in rats had a synergistic and more powerful effect. Vitamin C shows excellent in vitro results as an antibacterial and anti-biofilm agent. Vitamin C should be routinely prescribed with antibiotics to treat bacterial infections in the clinical setting.