摘要

       来自点源的城市流域是抗生素抗性基因 (ARG) 的潜在储存库。然而，很少有研究调查非点源的城市流域。为了了解可能携带此类基因的 ARG 和细菌的类型，我们调查了两个具有不同土地利用概况的非点源城市流域。使用异养平板计数 (HPC) 作为培养方法检查了两个流域 (R1、R3) 的抗生素耐药性水平，以获得对属于不同类别的七种抗生素（红霉素、卡那霉素、林可霉素、诺氟沙星、磺胺、四环素和甲氧苄啶）。在 HPC 研究中，239 种抗生素耐药细菌被表征为对更多抗生素具有耐药性。此外，使用 GeoChip 5.0 版鉴定了 ARG 和抗菌生物合成基因，以阐明流域 R1 和 R3 中地表水的抵抗力。HPC 研究表明，R1 的水样中对红霉素、卡那霉素、诺氟沙星、磺胺、四环素和甲氧苄啶具有抗药性的细菌数量明显高于 R3（相似性分析 (ANOSIM)，R = 0.557，p < 0.01）。在测试的七种抗生素中，耐林可霉素和甲氧苄啶的细菌数量较多。 239 种抗生素耐药菌株代表了耐药细菌种群的一个子集，包括以前不知道耐药性的细菌。大多数分离株对氨苄青霉素、万古霉素、林可霉素和甲氧苄啶有耐药性。GeoChip 在两个流域中显示出相似的 ARG，但 R1 中 tetX 和 β-内酰胺酶 B 基因的强度明显高于 R3。 R1 和 R3 中具有最高平均归一化强度的基因分别是四环素 (tet) 和磷霉素 (fosA) 抗性基因。 R1 中更高丰度的 tetX 基因与在 R1 样品中观察到的更高丰度四环素抗性 HPC 一致。外排泵与抗菌生物合成基因的强相关性 (r ≥ 0.8) 表明，在没有来自人为来源的抗生素的情况下，抗菌剂的自然产生可能充当转运蛋白的选择压力。
总之，不同土地利用概况的非点源城市流域中存在不同的抗生素抗性细菌系统发育型和多种 ARG，表明 ARG 风险评估和监测研究需要包括这些类型的流域。

       Urban watersheds from point sources are potential reservoirs of antibiotic resistance genes (ARG). However, few studies have investigated non-point source urban watersheds. In order to understand the types of ARG and bacteria that may carry such genes, we investigated two non-point source urban watersheds with different land use profiles. Heterotrophic Plate Count (HPC) was used as a culture method to examine the antibiotic resistance levels of two watersheds (R1, R3) to obtain resistance to seven antibiotics belonging to different categories (erythromycin,kanamycin, Lincor) Tetracycline, norfloxacin, sulfa, tetracycline and trimethoprim). In the HPC study, 239 antibiotic-resistant bacteria were characterized as resistant to more antibiotics. In addition, GeoChip version 5.0 was used to identify ARG and antibacterial biosynthesis genes to clarify the resistance of surface water in the basins R1 and R3.HPC research shows that the number of bacteria resistant to erythromycin, kanamycin, norfloxacin, sulfa, tetracycline and trimethoprim in the water sample of R1 is significantly higher than that of R3 (Analysis of Similarity (ANOSIM), R = 0.557, p <0.01). Among the seven antibiotics tested, the number of bacteria resistant to lincomycin and trimethoprim was higher. The 239 antibiotic-resistant strains represent a subset of the population of resistant bacteria, including bacteria for which resistance was not previously known. Most isolates are resistant to ampicillin, vancomycin, lincomycin and trimethoprim.GeoChip showed similar ARGs in the two watersheds, but the intensity of the tetX and β-lactamase B genes in R1 was significantly higher than that in R3. The genes with the highest average normalized strength in R1 and R3 are the tetracycline (tet) and fosfomycin (fosA) resistance genes, respectively. The higher abundance of the tetX gene in R1 is consistent with the higher abundance of tetracycline-resistant HPC observed in the R1 sample. The strong correlation between the efflux pump and antimicrobial biosynthesis genes (r ≥ 0.8) indicates that in the absence of antibiotics from man-made sources, the natural production of antimicrobial agents may act as a selective pressure for transporters.In short, there are different antibiotic-resistant bacterial phylogenetic types and multiple ARGs in non-point source urban watersheds with different land use profiles, indicating that ARG risk assessment and monitoring studies need to include these types of watersheds.

https://www.sciencedirect.com/science/article/abs/pii/S0043135416307096