Investigation of Antimicrobial and Anti-Quorum Sensing Properties of Some Derivatives of Cephalosporanic Acid, Ciprofloxacin, Norfloxacin, and Penicillanic Acid

Objective: The rapid increase of antibiotic resistance among bacteria is a serious public health problem. Studies have focused on the discovery of new antibiotic molecules and the development of new therapeutic strategies to combat these resistant bacteria. Once it was known that pathogenic bacteria regulate synthesis of virulence factors by the quorum sensing (QS) mechanism, QS inhibition became an attractive target for antibacterial treatment. This study aimed to investigate the antimicrobial activities and anti-QS properties of 16 derivatives of cephalosporanic acid, ciprofloxacin, norfloxacin, and penicillanic acid. Methods: Antimicrobial activity of the derivatives was tested by the agar well diffusion method against various microorganisms. The minimum inhibitory concentration (MIC) of effective derivatives was assessed by the broth microdilution method. Anti-QS properties were investigated using the soft agar method, observing inhibition of violacein production in Chromobacterium violaceum. The data were compared statistically.Results: Six norfloxacin derivatives displayed antimicrobial activity against a number of organisms, three of which were more effective than control antibiotics (p<0.05) against some organisms. One ciprofloxacin derivative demonstrated antimicrobial activity against all tested bacteria and was more effective against some bacteria than control antibiotic (p<0.05). The MIC values of these six norfloxacin and one ciprofloxacin derivatives were between 0.04–6.25 µg/mL and 0.04–3.12 µg/mL, respectively. A cephalosporanic acid and a penicillanic acid derivative displayed anti-QS properties.Conclusion: This study shows that some new derivatives of cephalosporanic acid, ciprofloxacin, norfloxacin, and penicillanic acid may have potential for development of new antibacterial and anti-QS agents.