Development of pyrazole and pyrazolopyrimidine derivatives as promising anti-MRSA agents targeting penicillin-binding protein (PBP2a) and mecA gene

Global health is threatened by methicillin-resistant S. aureus (MRSA). The rising prevalence of MRSA complicates anti-infective treatment strategies, highlighting the urgent need for novel therapeutics targeting MRSA. In this study, novel pyrazole and pyrazolopyrimidine derivatives were synthesized and comprehensively characterized using IR, 1H/13C NMR, and elemental analysis. Significant anti-microbial activity of these derivatives was demonstrated (using MIC test) against both Gram-positive (S. aureus ATCC 25923 and MRSA ATCC 43300) and Gram-negative bacteria (E. coli ATCC 25922 and K. pneumoniae ATCC 700603), in addition to exhibiting antifungal activity against C. albicans ATCC 10231. Notably, the Schiff bases pyrazoles 6b and 6c represent the most promising derivatives in comparison to the positive control drugs (neomycin sulfate and fluconazole). Additionally, MBC/MFC tests exhibited bactericidal and fungicidal activity, except for pyrazole derivative 3a, which demonstrated bacteriostatic efficacy specifically against MRSA. The promising compounds 6b and 6c showed strong antibiofilm activity against MRSA, resulting in a reduction of biofilm formation by 74.1 % and 71.36 %, respectively, at ½ MIC. Schiff base pyrazoles (6b and 6c) showed specific activity against MRSA, by revealing a reduction in expression of PBP2a protein levels using Western blotting. Additionally, polymerase chain reaction and sequencing of the mecA gene confirmed induced mutations following exposure to these compounds, suggesting a dual mechanism of action at both phenotypic and genotypic levels. Finally, the in-silico ADME studies for the promising derivatives were successful in predicting their oral bioavailability, drug-likeness, and pharmacokinetic features. © 2025 Elsevier Inc.