Combating Acinetobacter baumannii Biofilms Using Shigella flexneri Extracellular Metabolites and Cytocompatibility in...

Bacterial biofilms constitute a critical challenge to public health worldwide. The prevalence of antibiotic-resistant Gram-negative bacteria implicated in biofilm formation has increased globally, especially among pathogens connected to healthcare facilities. Acinetobacter baumannii (A. baumannii) is an opportunistic pathogen, known for its antibiotic-resistant strains that cause healthcare-associated infections (HAIs). The clinical strains of A. baumannii can develop biofilms on various biotic and abiotic surfaces, enhancing colonization of medical devices, thereby contributing to healthcare-associated infections. However, the lack of effective treatment options raises significant concerns regarding human infections caused by A. baumannii strains. The limited availability of effective antibiotics has encouraged the development of alternative antimicrobial approaches, such as using bacterial metabolites. Here, a Shigella flexneri strain was isolated from the human gastrointestinal tract and its crude extracellular metabolite was extracted. The antibiofilm efficacy of Shigella flexneri-derived crude extracellular metabolite (SFEM) was evaluated by using the crystal violet assay and fluorescence imaging. Substantial growth inhibition was observed at 100 μg/mL, while the minimum bactericidal concentration (MBC) was determined as 100 μg/mL. The MTT assay for cytotoxicity on Jurkat cells showed that SFEM did not significantly lower cell viability across the range of concentrations tested. The study demonstrates the potential of bacterial metabolites as antibiofilm agents against A. baumannii biofilms and supports further investigation of their bioactive properties. The overall experimental workflow of the present study is illustrated in the graphical abstract.