engleski

Nickel ions released from orthodontic appliances could diminish the susceptibility of Staphylococcus aureus to antibiotic ciprofloxacin

AIMS: To determine the effect of nickel ions which can be released from orthodontic appliances on the commensal bacteria and to evaluate whether they affect the development of bacterial resistance. Model bacteria Staphylococcus aureus ATCC 29213 was used. It is a commensal bacteria, but is found to be pathogenic in several diseases like skin and airway infections, and as such its susceptibility to antibiotics is of clinical importance. Materials and methods: Staphylococcus aureus was grown on the Mueller-Hinton agar. Solution of NiCl2x6H20 adjusted to the pH of 7 was used to simulate the effect of Ni2+ ions. Minimal inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of antibiotic ciprofloxacin and Ni2+ were determined by broth dilution method according to EUCAST (European Committee on Antimicrobial Susceptibility Testing). Growth kinetics of the bacteria in presence of both mentioned agents were monitored by measuring optical density at 620 nm (OD620) for 24 hours at 37°C. The model of interaction of ciprofloxacin and Ni2+ was evaluated by a modified checkerboard method and growth curves were obtained. Results: MIC for Ni2+ was 500 µg/mL and for ciprofloxacin 2.5 µg/mL. Bactericidal concentrations were 1000 µg/mL and 10 µg/mL for Ni2+ and ciprofloxacin, respectively. Growth curves confirmed the obtained MIC and MBC. As for the interaction of Ni2+ and ciprofloxacin, interestingly, the growth curves demonstrate bacterial growth in presence of the previously confirmed bactericidal concentration of ciprofloxacin when low concentrations of Ni2+ (7.8 µg/mL) were present. OD620 values between the bacteria treated with a MBC of ciprofloxacin (10 µg/mL) and bacteria treated with a combination of 10 µg/mL of ciprofloxacin and 7.8 µg/mL of Ni2+ significantly differed (p>0.005). Conclusions: The inhibitory concentration of nickel ions on S. aureus is way above the concentrations released from orthodontic appliances and wires. However, much lower concentrations, 70-fold than the MIC, which theoretically could be accumulated through increased corrosion of nickel from orthodontic appliances seem to act as antagonists on antibiotic therapy.

antibiotic ; metals ; orthodontic appliances

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