New antimicrobial agents are urgently needed to address the emergence of multi-drug resistant organisms, especially those active compounds with new mechanisms of action. Based on the molecular structures of the FtsZ inhibitors reported, a variety of thiazole-quinolinium derivatives with aliphatic amino and/or styrene substituents were synthesized from benzothiazolidine derivatives. In the present study, to further explore the antibacterial potential of thiazole-quinolinium derivatives, several Gram-positive and Gram-negative bacteria were treated with the newly modified compounds and the biological effects were studied in detail in order to understand the bactericidal action of the compounds. Our findings reveal that some of these derivatives possess good potent bactericidal activity as they can inhibit Gram-positive methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus and also some Gram-negative organisms and NDM-1 Escherichia coli. Furthermore, compounds 4a1-4a4 and 4b1-4b4 altered the morphology of bacterial cells and the cells displayed a more-elongated shape compared to the untreated cells. Biochemical assays showed that 4a4 and 4b4 stimulate FtsZ polymerization in bacterial cells, which eventually disrupts its dynamic assembly and Z-ring formation. The inhibition of this crucial step in bacterial cell division could potentially represent their main mechanism of antibacterial activity. Cytotoxicity assay and hemolysis assay suggested that 4a4 and 4b4 possess low cytotoxicity. In summary, these results further highlight the importance of 4a4 and 4b4 that could be developed as potent and effective bacteriostatic agents against multi-drug resistant bacteria.

BACKGROUND:The prevalence of drug-resistant bacterial infections urges the development of new antibacterial agents that possess a mechanism of action different from traditional antibiotics. FtsZ has been recognized as a key functional protein in bacterial cell division and it is currently believed to be a potential target for the development of novel antibacterial agents.PURPOSE:The primary aim of the study is to screen out an inhibitor targeting at FtsZ and followed to investigate its antibacterial activity and mode of action.METHODS:Cell-based cell division inhibitory screening assay, antimicrobial susceptibility test, minimum bactericidal concentration assay, time-killing curve determination, FtsZ polymerization assay, GTPase activity assay, and molecular modeling were performed in the present study.RESULTS:The screening study from a small library consisting of benzimidazole and indole derivatives discovered a compound (CZ74) with an indole-core structure. The compound exhibited strong cell division inhibitory effect. In addition, CZ74 shows high antibacterial potency against a number of tested Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. The minimum inhibitory concentration values obtained were within the range of 2-4 µg/mL. The results of biological study revealed that CZ74 at 2 µg/mL is able to disrupt FtsZ polymerization and inhibit GTPase activity and cell division. From molecular modeling study, CZ74 is found possibly binding into the interdomain cleft of FtsZ protein and then leads to inhibitory effects.CONCLUSION:This indole-cored molecule CZ74 could be a potential lead compound and could be further developed as a new generation of antibacterial agents targeting FtsZ to combat against multidrug-resistant bacteria.

The issue of multidrug resistant bacteria is a worldwide health threat. To develop new antibacterial agents with new mechanisms of action is thus an urgent request to address this antibiotic resistance crisis. In the present study, a new thiophenyl-pyrimidine derivative was prepared and utilized as an effective antibacterial agent against Gram-positive strains. In the tests against MRSA and VREs, the compound showed higher antibacterial potency than that of vancomycin and methicillin. The mode of action is probably attributed to the effective inhibition of FtsZ polymerization, GTPase activity, and bacterial cell division, which cause bactericidal effects. The compound could be a potential candidate for further development as an effective antibiotic to combat drug-resistant bacteria.

The antibacterial activity and the synergistic effect with β-lactam antibiotics of a new 1-methylquinolinium iodide derivative were investigated. The experimental results indicate that the compound possesses a strong antibacterial activity against a panel of bacteria including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus and NDM-1 Escherichia coli with the MIC values from 0.75 μg/mL to 6 μg/mL. In addition, this compound combined with β-lactam antibiotics shows strong synergistic antimicrobial activities against antibiotic-resistant strains of S. aureus. The results of biochemical studies also reveal that this compound can effectively disrupt GTPase activity, polymerization of FtsZ, and cell division to cause cell death. The compound shows high potential for further development as a new generation of antibacterial agents to fight against the emergence of multidrug-resistant bacteria.