ANTIBACTERIAL ACTIVITY OF PYRIMIDINE DERIVATIVES WITHOUT DETECTABLE RESISTANCE

MARTINEZ FLORENCIA; LUJAN ADELA M. ; DÍAZ IVÁN; COBO JUSTO; ENRIZ RICARDO DANIEL ; CARPINELLA M CECILIA

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2022

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular

Antibacterial resistance is an urgent concern in health care due to the lack of effective antibacterialtherapeutic entities. The development of new antibiotics, particularly those with novel mechanisms of action (MOA) and that are active against multidrug-resistant pathogens, is of major interest in this context. Pyrimidine and its derivatives are known to have versatile pharmacological activities, especially as potential antibacterials. In this work, the antibacterial activity of a series of 28 synthetic pyrimidine derivatives was evaluated. These derivatives had been synthesized with a p-chlorophenyl or a naphthyl group as the hydrophobic tail, a pyrimidine unit as the backbone, a 1-phenylpropenone or a piperazine ring or an aminophenyl fragment as the linker chain joint to a quinolone moiety as the polar head. The antibacterial activity was determined against two Gram-positive bacteria: Staphylococcus aureus methicillin sensitive and resistant (MSSA and MRSA) and Bacillus subtilis ; and two Gram-negative bacteria: Pseudomonas aeruginosa and Escherichia coli . Compounds 7b, 5b and 10a showed to be effective against MSSA, MRSA and B. subtilis , being 5b the most potent against MSSA (MIC = 4 μg/mL) and B. subtilis (MIC = 8 μg/mL). Compounds 7b and 10a also inhibited E. coli growth, being 7b the most active (MIC = 16 μg/mL). Time kill curves were performed in MSSA and a bactericidal effect was observed for the compounds. The checkerboard assay was used to detect combination effects of active compounds and commercially available antibiotics against MSSA. Gentamicin and 5b combination resulted in synergistic antibacterial effects against this strain. Bacterial cytological profiling was performed in order to identify the MOA of these compounds. Bacteria treated with 7b showed smaller cells and a more condensed chromosome compared to untreated cells. Cell membrane staining in these cells was uneven showing increased fluorescence intensity in the cell poles. Also, membrane integrity was compromised since SYTOX Green fluorescence signal was detected. These cytological profiles resemble cells treated with compounds that disrupt cell membranes. Finally, it was found that these compounds could avoid development of resistance. This observation was supported by the fact that no resistant mutants of MSSA were isolated after 14 days of experimental evolution under the presence of different concentrations of each compound. These results suggest that compounds 5b, 7b and 10a could serve as promising leads for the development of potential antibacterial agents with low-level of resistance that probably affect the cell membrane.