Vitamin C effect on biofilm-forming ability of drug-resistant Acinetobacter baumannii clinical isolates

Background: Multidrug-resistant Acinetobacter baumannii, particularly strains that produce metallo-β-lactamase (MBL) and carbapenemase, are considered emerging infection control threats. Its antimicrobial resistance and ability to form biofilm make treatment difficult. Although early research suggests that vitamin C can break down biofilms and restore antibiotic activity, its efficacy against drug-resistant A. baumannii strains is still unclear. The aim of this study was to assess the antimicrobial and biofilm inhibition properties of vitamin C against drug-resistant A. baumannii strains. Methods: Fifty clinical isolates of A. baumannii were collected from Assiut University Hospitals, Egypt. PCR detection of blaOXA-51-like gene was used for species confirmation. Antimicrobial susceptibility testing, β-lactamase phenotyping, and biofilm-forming assay were conducted. Broth microdilution was used to determine vitamin C minimum inhibitory concentration (MIC), and anti-biofilm activity was screened at sub-inhibitory concentrations. Results: Out of the A. baumannii isolates, 98% were classified as XDR and 2% were PDR. Carbapenemase and MBL enzyme production were detected in 52% and 66% of isolates, respectively. Strong biofilm formation was detected in 86% of isolates, with no significant association between biofilm production and resistance pattern. Vitamin C showed a microbial inhibition effect with an MIC range of 3.125-12.5 mg/mL, which is dose dependent. At sub-MICs, vitamin C reduced biofilm-forming ability significantly by 44.93% at ½ MIC and 33.17% at ¼ MIC. Conclusion: Vitamin C showed significant antimicrobial and anti-biofilm activity against XDR and PDR A. baumannii isolates, particularly against strong biofilm-forming strains, supporting its role as an alternative anti-biofilm agent in managing resistant infections.