[Deceleration of bacterial growth in Staphylococcus aureus and Pseudomonas Aeruginosa cultures in the presence of copper and zinc cations].

Abstract

AIM: Evaluate antibacterial effects of millimole concentrations of copper and zinc cations used as sulfates or chlorides in S. aureus and P. aeruginosa cultures. MATERIALS AND METHODS: Suspension of S. aureus or P. aeruginosa containing 108 CFU/ml were lawn-seeded onto Petri dishes with nutrient agar. 30 minutes later salt solution of copper or zinc with concentrations by metal cation from 10(-9) or 10(-6) M to 5 x 10(-1) M were applied to the surface of the lawn by 5 μ drops using a 36-channel stamp-replicator. Dishes with bacterial cultures were then incubated for 16-18 hours at 37°C, and diameter of growth inhibition zone was measured afterwards. For evaluation of the presence (absence) ofviable bacteria in growth inhibition zones, seeding of the material from the center of the zone was carried out into tubes with nutrient broth that were thermostated up to 5 days at 37°C, clarity of the nutrient broth was then evaluated. RESULTS: Inhibiting effects of zinc sulfate against S. aureus surpass effects of copper sulfate by 1.3-1.6 times (p < 0.001-0.05) within metal concentrations from 50 to 500 MM. The effects of zinc chloride in S. aureus culture surpass effects of copper chloride by 1.2-1.6 times (p < 0.02) for cation concentrations of 100 and 500 mM. In P. aeruginosa cultures, antibacterial effects of copper sulfate are comparable with effects of zinc sulfate. The effects of copper chloride on P. aeruginosa cells are 1.2 times more pronounced (p < 0.05) than effects of zinc chloride for metal concentration of 500 mM. Material seeding from zones of culture growth suppression detects turbidity of nutrient broth in samples with specimens from wells treated with zinc salts and broth clarity in samples from wells treated with copper salts. CONCLUSION: In millimole con- centrations, copper and zinc cations have pronounced antibacterial effects in cultures of S. aureus and P. aeruginosa. It is realized as bactericidal in the presence of copper cations and bacteriostatic - in the presence of zinc cations. S. aureus bacteria turn out to be more sensitive to the effects of zinc cations, evaluated by zones of growth inhibition, than P. aeruginosa. The latter show a higher, than S. aureus, tolerance to copper and zinc. Wherein, P. aeruginosa toler- ance to copper cations is surmountable.