Evaluation of the Antibacterial Activity of Isatin against Campylobacter jejuni and Campylobacter coli Strains

Antibiotic resistance, particularly against fluoroquinolones and macrolides, has emerged globally among thermophilic Campylobacters (Campylobacter jejuni and Campylobacter coli), giving rise to concerns about the efficacy of antibiotic treatment of these bacteria. Thus, developing new antibacterials with excellent activity is important. Isatin (IST) and its derivatives have exhibited promising antibacterial activities in several pathogenic bacteria. However, its activity against Campylobacter is unknown. Therefore, this study was conducted to evaluate the antibacterial activity of isatin against 29-Campylobacter strains (C. jejuni-17 and C. coli-12) and investigate the effects at the cellular level. The minimal inhibitory concentrations (MICs) of isatin were between <1.0 and 16.0 µg/mL in Campylobacter strains. Most strains presented with MIC = 8.0 µg/mL (76%). The minimal bactericidal concentration (MBC) was determined to be 16.0 µg/mL for 72% of the Campylobacter strains tested. The 50% inhibitory concentration (IC50) value for isatin was 125.63 µg/mL on the MRC-5 normal cell line, suggesting that isatin can be considered a safe substance in terms of cytotoxicity. In this study, we demonstrated the potential of isatin based on its low toxicity and effectiveness in vitro against antibiotic-resistant Campylobacter strains, which indicates that this compound could be an attractive candidate for future use in multidrug-resistant Campylobacter treatment.