title: Lacunary-substituted undecatungstosilicates sensitize methicillin-resistant Staphylococcus aureus to beta-lactams.
abstract: Some Keggin-structural (hetero)polyoxotungstates with a lacunary hole, such as undecatungstosilicate ([SiW11O39]8-, SiW11), greatly sensitize methicillin-resistant Staphylococcus aureus (MRSA) to beta-lactams. In this study, the effects of lacunary-substituted derivatives of SiW11 were tested to determine if the lacunary hole is required for the sensitizing effect. Initially, it was supposed that the hole functioned as a binding site that interacts with some bacterial components. However, most of the lacunary-substituted species had stronger effects than SiW11, indicating that the hole is not essential for the sensitizing effect. Undecatungsto(ferri)ferrosilicate ([SiW11O39Fe](6/5-)) was the most potent compound tested, but undecatungstocobaltosilicate ([SiW11O39Co]6-) gave better results according to the fractional inhibitory concentration index. Small lipophilic cations enhanced the sensitizing effect, but bulky cations inhibited it. This suggests that a charge interaction between the tungsten compounds and some unknown materials in the culture medium or bacterial cells plays an important role in the sensitizing effect.
authors.affiliation: Clinical Laboratory, Saga Medical School Hospital, Nabeshima, Japan. tajima@post.saga-med.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Tajima
mesh_terms: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003460:Crystallization; D006863:Hydrogen-Ion Concentration; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D008968:Molecular Conformation; D017640:Silicates / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects*; D017973:Tungsten Compounds / Q000494:pharmacology*; D047090:beta-Lactams
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D017640:Silicates; D017973:Tungsten Compounds; D047090:beta-Lactams