IITR00803: a benzoxazole-nitrothiophene small molecule with broad-spectrum antibacterial potential

The drug discovery of novel antibacterials is pivotal to combat the ever-growing challenge of antibiotic resistance. The current antibiotics in clinics target the essential pathways in bacteria. However, drug efflux among other resistance mechanisms remains a persistent problem, leading to reduced efficacy of antibiotics. In the present study, we report the discovery of a novel small molecule, IITR00803, with antibacterial properties. IITR00803 demonstrated broad-spectrum antibacterial activity with potent inhibition of enteric pathogens. The small molecule contains a benzoxazole group and a nitrothiophene moiety in its chemical structure. The nitrothiophene-based compounds are prone to efflux by AcrAB-TolC efflux pumps. Despite containing the nitrothiophene group, IITR00803 did not demonstrate efflux liability, thereby demonstrating a broad antibacterial spectrum. The small molecule depicted bactericidal activity against Salmonella enterica serotype Typhimurium with a post-antibiotic effect of ~1.51 h. The mode of action studies revealed the membrane potential perturbing properties of IITR00803 against S. enterica serovar Typhimurium and Escherichia coli, whereas DNA-damaging activity was observed against E. coli. Resistance development studies on IITR00803 in laboratory growth media showed that S. enterica serovar Typhimurium could not develop stable resistance against this molecule under the tested conditions. Furthermore, IITR00803 exhibited non-toxic potential against eukaryotic cells and the model organism Caenorhabditis elegans. The compound also depicted efficacy against the C. elegans infection model of S. enterica serovar Typhimurium. Collectively, our results show that IITR00803 is a broad-spectrum antibacterial small molecule that alters membrane potential and exhibits in vitro and in vivo safety and efficacy.IMPORTANCEAntimicrobial resistance is a growing global health threat, necessitating the urgent development of novel antibacterial agents. Salmonella infections, particularly those originated by non-typhoidal serovars such as Salmonella enterica Typhimurium and S. enterica Enteritidis, contribute significantly to morbidity and mortality worldwide. These foodborne pathogens cause severe gastroenteritis and spread through poor sanitation and food safety measures, leading to millions of infections each year. The emergence of multidrug-resistant Salmonella strains has further complicated treatment by limiting the therapeutic options. This crisis highlights the need for the discovery of new therapeutic options that impede the resistance development of bacterial pathogens and demonstrate the potential to overcome existing antibiotic resistance mechanisms.