Metal Ion Zeolite Materials against Resistant Bacteria, MRSA

Metal ion-zeolite materials based on different zeolite structures – FAU (NaY, 100 to 750 nm), LTA (4400 nm) and MFI (ZSM5, >100, 760 and 2500 nm) - were studied for developing antimicrobial agents using a simple method. These zeolite structures were loaded with silver, copper or zinc ions by ion-exchange method and tested for antimicrobial activity against three bacteria - Escherichia coli, methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA), a clinical isolate. Sample characterization confirmed the presence of metal ions and the stability of the zeolite structures. All mono and bimetallic-ion zeolite materials loaded with silver display higher antimicrobial activity than zinc or copper-containing samples. The inhibitory effect of metal ion-zeolite materials was even higher than the action of antibiotics, especially against MRSA. These findings show that silver ion-zeolite materials have potential applications to combat bacterial infections and further prevent the prevalence of resistant microorganisms. Antimicrobial activity seems to be related to the acidity and Si/Al ratio of zeolites, according to the following scale: MFI > FAU > LTA. Particularly, the inhibitory effect against MRSA is a very promising result considering the difficulty of an effective eradication of this resistant strain, the principal agent of nosocomial or healthcare-associated-infections (HAI), which affect 3.2 % of all hospitalized patients in the United States and 6.5 % in the European Union.