Antibacterial activity of modified natural clinoptilolite against clinical isolates of Acinetobacter baumannii

The antibacterial activity of natural zeolite (NZ) containing 2.03 wt.% of Cu2+ (CuNZ), 5.07 of Ag+ (AgNZ) or 8.50 of benzalkonium ion (BCNZ) were tested against clinical isolates of Acinetobacter baumannii belonging to European clone I and II. Isolate from clone II was more sensitive to CuNZ and AgNZ with minimum bactericidal concentration (MBC) 125 and 31.2 mg L-1, respectively than isolate from clone I with MBC of 250 mg L-1 for both CuNZ and AgNZ. Isolate from clone I was more sensitive to BCNZ with MBC 250 mg L-1 than isolate from clone II with MBC 500 mg L-1. The minimum inhibitory concentration (MIC) values were the same or slightly lower than the MBC values. The antibacterial activity of CuNZ, AgNZ and BCNZ against the A. baumannii European clone I and II was due to the activity of cations loaded onto NZ while not to the NZ used as support material. The antibacterial activity of CuNZ, AgNZ and BCNZ opens a possibility of future clinical investigations and its application. (C) 2012 Elsevier Inc. All rights reserved.