Diffuse environmental antibiotic and antibiotic resistance gene contamination is increasing human and animal exposure to these emerging compounds with a consequent risk of reduction in antibiotic effectiveness. The present work investigated the effect of the antibiotic sulfamethoxazole (SMX) on growth and antibiotic resistance genes of a microbial community collected from an anaerobic digestion plant fed with cattle manure. Digestate samples were used as inoculum for concentration-dependent experiments using SMX at various concentrations. The antibiotic concentrations affecting the mixed microbial community in terms of growth and spread of resistant genes (sul1, sul2) were investigated through OD (Optical Density) measures and qPCR assays. Moreover, SMX biodegradation was assessed by LC-MS/MS analysis. The overall results showed that SMX concentrations in the range of those found in the environment did not affect the microbial community growth and did not select for antibiotic-resistant gene (ARG) maintenance or spread. Furthermore, the microorganisms tested were able to degrade SMX in only 24 h. This study confirms the complexity of antibiotic resistance spread in real matrices where different microorganisms coexist and suggests that antibiotic biodegradation needs to be included for fully understanding the resistance phenomena among bacteria.

中文翻译：

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磺胺甲基异恶唑对天然微生物群落生长和抗生素抗性的影响

扩散的环境抗生素和抗生素抗性基因污染正在增加人类和动物对这些新兴化合物的接触，从而降低抗生素效力。本工作调查了抗生素磺胺甲恶唑（SMX）对从饲喂牛粪的厌氧消化植物中收集的微生物群落的生长和抗生素抗性基因的影响。消化液样品用作接种物，用于使用各种浓度的SMX进行浓度依赖性实验。就抗性基因的生长和扩散而言，抗生素浓度会影响混合微生物群落（苏尔1，苏尔2）通过OD（光学密度）测量和qPCR分析进行了研究。此外，通过LC-MS / MS分析评估了SMX的生物降解。总体结果表明，在环境中发现的SMX浓度范围不会影响微生物群落的生长，也不会选择抗生素抗性基因（ARG）的维持或扩散。此外，测试的微生物仅能够在24小时内降解SMX。这项研究证实了抗生素耐药性在不同微生物共存的真实基质中传播的复杂性，并建议需要包括抗生素生物降解，以充分了解细菌之间的耐药性现象。