THE INFLUENCE OF HEAVY METALS AND ANTIMICROBIAL ON STAPHYLOCOCCUS AUREUS AND PSEUDOMONAS AEROGINOSA ISOLATES

Abstract

Two isolates of Staphylococcus aureus and Pseudomonas aeroginosa of bacteria were exposed to different concentrations ( 5 , 10 or 25 mg /l )of heavy metals ions ( Silver Ag2+ , Cobalt Co2+ or Lead Pb2+) for different exposure periods ( 0 , 1, 2, 24 and 48 hrs.) .The results showed that the inhibitory effect of these metals on the growth of the two isolates were in the following sequences :- Pb < Co < Ag Some of these metals caused an elongation of lag phase in liquid medium for these isolates . Whene antibiotic discs ( chloramphenicol 30 mcg , clindamycin 2 mcg , erythromycin 15 mcg , gentamycin 10 mcg ,tetracyclin 30 mcg and vancomycin 30 mcg ) were added to solid medium which was previously supplemented with the above heavy metals ions , a synergestics effect was observed between antibiotics and heavy metals ions ( specially silver ions at 25 mg/ l )to increase the inhibition zone significantly ( P < 0.01 ) for both isolates .