INTERNATIONAL JOURNAL OF ADVANCE RESEARCH
IN MULTIDISCIPLINARY

Antimicrobial resistance continues to erode the effectiveness of established antibacterial therapy and places a premium on chemically tractable series that retain activity against clinically relevant resistant organisms. This study examines a ten-member thiazole-Schiff base hybrid series (SJ-1-SJ-10) across methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), multidrug-resistant Escherichia coli, KPC-producing Klebsiella pneumoniae and multidrug-resistant Pseudomonas aeruginosa. The available compound records showed isolated yields of 68-84%, melting points of 142-183 °C and HPLC purities of 97.2-99.1%. Broth microdilution data demonstrated a clear within-series potency gradient. SJ-7, labelled as the 4-CF3 analogue in the source dataset, was the most active compound, with MIC values of 2, 4, 16, 16 and 64 µg/mL against MRSA, VRE, MDR E. coli, K. pneumoniae and P. aeruginosa, respectively. SJ-6 and SJ-9 formed a second activity tier, whereas SJ-1 was consistently weaker. For SJ-7, MBC values were two-fold above the MIC across the bacterial panel. The pattern supports a provisional structure-activity relationship in which selected electron-withdrawing para substituents are associated with improved whole-cell activity, although the Gram-negative spectrum remained constrained, particularly against P. aeruginosa.