Antibiotics are extremely effective against bacterial infections due to their selective toxicity for bacteria rather than the host. Extensive use and misuse of antibiotics resulted in significant increases in antibiotic levels in aquatic and soil environments. Bacteria exposed to antibiotics with low concentrations may develop antibiotic resistance. In this study a swelling 2:1 clay mineral montmorillonite (MMT) and a non-swelling 1:1 clay mineral kaolinite were premixed with tetracycline (TC) of varying concentrations. The gram-negative bacteria Escherichia coli (E. coli) and Salmonella enterica (S. enterica) of both TC sensitive and TC resistant strains were tested for their growth in the presence TC-loaded clay minerals of different amounts and under different physico-chemical conditions. The antimicrobial activity of TC was significantly decreased in the presence of MMT. In the absence of MMT, no bacteria growth was found at a TC concentration 0.25mg/mL and above. On the contrast, in the presence of MMT, 50% growth was still found for a TC resistant E. coli at a TC concentration of 5mg/g. The influence of kaolinite was to a lesser degree. These results suggest that antimicrobial agents present in clayey soils could be responsible for possible mutation of bacteria of high antibiotic resistance.

中文翻译：

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四环素-粘土相互作用对细菌生长的影响。

抗生素由于对细菌而非宿主具有选择性毒性，因此对细菌感染极为有效。大量使用和滥用抗生素导致水生和土壤环境中抗生素水平的显着增加。暴露于低浓度抗生素的细菌可能会产生抗生素耐药性。在这项研究中，将溶胀的2：1粘土矿物蒙脱石（MMT）和非溶胀的1：1粘土矿物高岭石与不同浓度的四环素（TC）预混。测试了TC敏感菌株和TC耐药菌株的革兰氏阴性细菌大肠埃希氏菌（E. coli）和肠炎沙门氏菌（S. enterica）在存在不同量和不同理化作用的TC加载的粘土矿物存在下的生长情况条件。在MMT存在下，TC的抗菌活性显着降低。在没有MMT的情况下，在TC浓度为0.25mg / mL及以上时，未发现细菌生长。相反，在MMT存在下，TC浓度为5mg / g的TC抗性大肠杆菌仍发现50％的生长。高岭石的影响程度较小。这些结果表明存在于粘性土壤中的抗微生物剂可能是造成高抗生素抗性细菌可能发生突变的原因。