Metal Ion–Zeolite Materials against Resistant Bacteria, MRSA

Abstract

Metal ion–zeolite materials based on different zeolite structuresFAU (NaY, 100–750 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 using an ion-exchange method and tested for antimicrobial activity against three bacteriaEscherichia coli, methicillin-sensitive Staphylococcus aureus, 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 displayed 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. The 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 effective eradication of this resistant strain, the principal agent of nosocomial or healthcare-associated infections, which affect 3.2% of all hospitalized patients in the United States and 6.5% in the European Union.

Waste Glass-Derived Tobermorite Carriers for Ag+ and Zn2+ Ions

“…The results obtained in the present study agree with those of other Ag + -and Zn 2+bearing zeolites and clays that report inferior metal ion-release [43] and smaller or absent clear zones in S. aureus and E. coli Kirby-Bauer assays for Zn 2+ relative to Ag + [30,43,44]. Although, conversely, one study observed similar zones of inhibition in a culture of S. aureus for montmorillonite clay loaded with either 0.24 mmol g −1 Ag + or 0.29 mmol g −1 Zn 2+ [46].…”

“…The use of natural and synthetic zeolites, clays, and silicate frameworks as carriers for antimicrobial Ag + and Zn 2+ ions has received increasing attention in the quest to control the transmission of pathogenic microorganisms [28,30,31,[41][42][43][44][45][46][47][48]. Silver ions are soft acids that target DNA and disrupt the chemistry of microbial metalloproteins involved in respiration, membrane structure, replication, and metabolism, by binding with thiol groups [49].…”

“…The uptakes of Ag + and Zn 2+ ions by the container glass-derived tobermorites in the present study are compared with those of other natural and synthetic silicate-based carriers reported in the recent literature in Table 3 [28,30,31,[41][42][43][44][45][46][47][48]. The uptakes of Ag + ions by the green and amber glass-derived tobermorites are within the reported range for zeolite Y [44,45] and greater than those of analcime [41], chabazite [31], and montmorillonite [48]. However, the extents of Ag + -loading of TG4 and TA4 are inferior to those of zeolites A [30,32] and X [43], ZSM-5 [45], clinoptilolite [47], and the titanosilicate frameworks JDF-L1 and AM-4 [46].…”

“…However, the extents of Ag + -loading of TG4 and TA4 are inferior to those of zeolites A [30,32] and X [43], ZSM-5 [45], clinoptilolite [47], and the titanosilicate frameworks JDF-L1 and AM-4 [46]. Zn 2+ -uptakes by TG4 and TA4 are comparable with that of titanosilicate AM-4 [46], superior to those of analcime [41], ZSM-5 [45], JDF-L1 [46], chabazite [31], clinoptilolite [47] and montmorillonite [48], and inferior to those of zeolites A [30,42], X [43] and Y [44,45].…”

“…Synthetic analcime [41] 0.30 0.028 Zeolite A [42] 3.55 1.52 Zeolite A [30] 1.22 2.81 Zeolite X [43] 3.95 2.77 Zeolite Y [44] 0.046-0.73 0.83 Zeolite Y [45] 3.13 1.19 Zeolite ZSM-5 [45] 1.11 0.32 Titanosilicate JDF-L1 [46] 0.82 0.16 Titanosilicate AM-4 [46] 1.33 0.57 Natural chabazite [31] 0.12 0.018 Clinoptilolite [47] 1.23 0.22 Montmorillonite [48] 0.24 0.29…”