Antibacterial activity of Zn-loaded Cuban zeolite against Helicobacter pylori in comparison to its Na-loaded and unmodified counterparts

• Published in: Environmental geochemistry and health 2021-05, Vol.43 (5), p.2037-2048
• Main Authors: Cerri, Guido, Farina, Mauro, Brundu, Antonio, Gavini, Elisabetta, Salis, Andrea, Dathe, Wilfried
• Format: Article
• Language: English
• Subjects: Ammonia; Ammonium; Ammonium compounds; Antibacterial activity; Antibiotics; Bacteria; Cations; Earth and Environmental Science; Environment; Environmental Chemistry; Environmental Health; Geochemistry; Growth; Helicobacter pylori; Ion exchange; Minimum inhibitory concentration; Original Paper; Public Health; Sodium; Soil Science & Conservation; Stomach; Subtraction; Survival; Terrestrial Pollution; Zeolites; Zinc
• ISSN: 0269-4042; 1573-2983
• DOI: 10.1007/s10653-020-00781-2

Helicobacter pylori can be found in the stomach of about half of the humans, and a large population can be associated with serious diseases. To survive in the stomach H. pylori increases the pH locally by producing ammonia which binds to H + becoming ammonium. This work investigated the effects on the in-vitro growth of H. pylori of a natural cation-exchanger mainly composed (≈70%) of clinoptilolite and mordenite. The zeolitized material from Cuba was evaluated in its original form ( M ), as well as in its Na- ( M-Na ) and Zn-exchanged ( M-Zn ) counterparts. In the preliminary agar cup diffusion test, H. pylori revealed susceptibility only to M-Zn , with a direct relationship between concentration and width of inhibition halo. Further experiments evidenced that bacterium replication increases when ammonium is supplied to the growth medium and decreases when zeolites subtract NH 4 + via ion exchange. Due to the multi-cationic population of its zeolites M was not effective enough in removing ammonium and, in the Minimum Inhibitory Concentration (MIC) test, allowed bacterial growth even at a concentration of 50 mg/mL. Inhibition was achieved with M-Na because it contained sodium zeolites capable of maximizing NH 4 + subtraction, although the MIC was high (30 mg/mL). M-Zn evidenced a more effective inhibitory capacity, with a MIC of 4 mg/mL. Zinc has antimicrobial properties and H. pylori growth was affected by Zn 2+ released from clinoptilolite and mordenite. These zeolites, being more selective towards NH 4 + than Zn 2+ , can also subtract ammonium to the bacterium, thus enhancing the efficacy of M-Zn .