Antibacterial Activity of Secondary Metabolites Produced by Candida albicans Against Multidrug-Resistant Escherichia coli Isolated from Urinary Tract Infections

Antimicrobial resistance (AMR) is a major clinical challenge which alter the efficacy of the therapy. The global emergence of multidrug-resistant (MDR) uropathogenic Escherichia coli (UPEC) is a major reason for the increasing severity and treatment difficulty of these bacterial infections. Due to the increasing incidence of antibiotic resistance, it is urgent to discover new biogenic molecules with antibiotic properties. The aim of this study was to examine how secondary metabolites produced by Candida albicans isolate may affect clinical isolates of MDR E. coli. C. albicans isolates were phenotypically identified by CHROMagar Candida and genotypically authenticated via ITS rDNA sequencing (GenBank Accession No. PZ101037). Clinical UPEC were isolated from urine specimens across the Damietta Governorate, Egypt, selectively screened using 2 mg/L ceftazidime, and verified via automated Vitek 2 systems. The extracellular metabolites were extracted using ethyl acetate, profiled via GC-MS, and tested for antibacterial activity using the agar well diffusion assay. Cytocompatibility was evaluated against normal human lung fibroblast (WI-38) cells. GC-MS chemical profiling resolved that the C. albicans extract was rich in bioactive principles, primarily dominated by 1-hexadecene (19.85%) and phenol, 2,4-bis(1,1-dimethylethyl)- (14.52%). The antibacterial activity of the C. albicans secondary metabolites was assessed using the agar well diffusion method, minimum inhibition concentration, and minimum bactericidal concentration against the E. coli strains. The crude extract exhibited powerful, dose-dependent antibacterial activity against all tested MDR UPEC strains, yielding a maximum zone of inhibition diameter of 35.12 ± 0.64 mm. Furthermore, in vitro safety assays demonstrated a highly favorable cytocompatibility profile, with an IC50 value of 120.5 µg/mL on normal WI-38 cellular matrices. These findings demonstrate that the C. albicans EGDA-F2 metabolic matrix holds substantial potential and rich with biogenic reservoir of active chemical scaffolds or therapeutic adjuvants to combat extensively drug-resistant UPEC infections.