ANTIMICROBIAL ACTIVITY OF CHROMIUM(III) COMPLEXES ON STAPHYLOCOCCUS AUREUS AND ESCHERICHIA COLI
Páez PL[1][*](1,2), Bongiovanni ME(2), Albesa I(2), Becerra MC(2) and Argüello GA(1,2).
(1)INFIQC-CONICET, Dpto. de Fisicoquímica; (2)Dpto. de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Ciudad Universitaria. 5000 Córdoba. República
Introduction. Since their discovery, antibiotics have played an important role in health care. However, the increasing emergence of antibiotic resistance among a variety of microbial pathogens stimulates intensive research efforts with the aim to identify alternative therapeutic approaches (1). Macrocyclic complexes have attracted attention because of their pharmacological properties, i.e. toxicity against bacterial and fungal growth. It was reported that complexes of chromium(III) would have a role in the microbiological application to reduce the virulence and antibiotic resistance (2). In the present work we report the biological activities of chromium(III) complexes against Escherichia coli and Staphylococcus aureus.
Materials and methods. Two test bacterial strains viz S.aureus ATCC 29213 and E.coli ATCC 25922 were considered for the determination of Minimum Inhibitory Concentration (MIC) of the synthesized complexes. The MIC of the compounds was evaluated by using the standard tube dilution method on Mueller Hinton broth. Bacterial growth was observed at 18 h of incubation, following the indications of the Clinical and Laboratory Standards Institute (CLSI) (3). The concentrations of the compounds were ranged from 0.004 to 2 µg/mL. In addition, the MIC of the ligands 1, 10-phenanthroline (phen) and dipyrido [3,2-a:2´,3´-c]-phenazine (dppz) was calculated. Dilutions of ciprofloxacin (0.008 to 4 µg/mL) were used to compare the activity. The lowest concentration of the compound that prevented bacterial growth was considered to be the MIC.
Results. Two chemically macrocyclic complexes and their ligands were screened for their in vitro antibacterial activity against S.aureus and E.coli. The phen and dppz ligands did not show activity against the two bacterial strains. [Cr(phen)2(dppz)]3+ was found to be the most potent. MIC values obtained for the chromium complexes were in the range of those obtained with ciprofloxacin. E.coli was found to be more susceptible to [Cr(phen)2(dppz)]3+ than S.aureus, with a MIC for E.coli of 0.125 µg/mL and a MIC for S.aureus of 0.5 µg/mL while the MIC for E.coli was 0.25 µg/mL and for S.aureus 1 µg/mL for [Cr(phen)3]3+. The complexes of chromium(III) exhibited higher antimicrobial activities against E.coli and S.aureus than the ligands alone.
Conclusions. The work provides the first evidence of antimicrobial activity of the synthetic metallomolecules [Cr(phen)3]3+ and [Cr(phen)2(dppz)]3+. Similar compounds have recently been synthesized, some of which may show a greater degree of antimicrobial activity. Future studies will be directed to determine the antimicrobial activity of these compounds, as well as the activity of metal complexes on (drug-resistant) pathogenic bacteria.
Acknowledgments. CONICET, SeCyT.
References.
1- Taylor PW, Stapleton PD, Luzio JP. New ways to treat bacterial infections. Drug Discov Today 2002;7:1086-1091.
2- Shrivastava HY, Devaraj SN, Unni Nair BJA. Schiff base complex of chromium(III): an efficient inhibitor for the pathogenic and invasive potential of Shigella dysenteriae. Inorg Biochem 2004;98:387-392.
3- Clinical and Laboratory Standards Institute (CLSI): Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically; Approved Standard - Seventh Edition. CSLI document M7-A7.
