Study on Nourseothricin and Its Activity Against Drug-Resistant Bacteria

Background: A global problem is created by the emergence of antimicrobial resistance, necessitating the development of new antimicrobials to ensure effectiveness. “The antimicrobial activity of nourseothricin against clinically significant drug-resistant bacterial pathogens is reported here, including methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum beta-lactamase (ESBL)” producing Escherichia coli, carbapenem-resistant “Klebsiella pneumoniae,” and vancomycin-resistant Enterococci (VRE). Methods: The antimicrobial activity of nourseothricin was evaluated through the use of standard microbiological assays. Minimal Inhibitory Concentrations (MICs) were determined by the broth microdilution method, following the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Sixty clinical isolates were included: MRSA (n=20), ESBL-producing E. coli (n=15), carbapenem-resistant K. pneumoniae (n=15), and VRE (n=10). Time-kill kinetics were assessed at concentrations of 0.5×, 1×, 2×, and 4× MIC. Results: Potent activity was displayed by nourseothricin against all tested strains, with MIC90 values of 4 μg/mL for MRSA, 8 μg/mL for ESBL E. coli, 16 μg/mL for carbapenem-resistant K. pneumoniae, and 8 μg/mL for VRE. Rapid bactericidal activity was demonstrated during time-kill studies, showing a ≥3-log₁₀ reduction in viable cell counts within 4.5 hours for MRSA and 5.2 hours for ESBL E. coli when exposed to 4× MIC. MIC values were found to be highly correlated with inhibition zone diameters (r = 0.89, p < 0.001), and reproducible activity was observed against both gram-positive and gram-negative resistant strains”. Conclusions: Significant potential for nourseothricin as a broad-spectrum antimicrobial against traditionally drug-resistant pathogens is indicated by the findings of this study. Rapid bactericidal activity, particularly against WHO priority pathogens, and a well-characterized mechanism of action suggest therapeutic applications. These results warrant further in vivo studies and clinical trials to evaluate nourseothricin’s potential for treating drug-resistant bacterial infections.