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近年来,抗生素在水土环境中被频繁检出,其对硝酸盐降解的反硝化作用产生不同程度的影响已被多项研究证实[1-2]. 然而,这些研究大多是在单一抗生素暴露条件下进行的. 实际上,在水土环境中检测到四环素类、磺胺类、喹诺酮类、大环内酯类、林可霉素类等多种不同种类及不同功能的抗生素共同存在[3-6]. 不同种类抗生素之间可发生协同、累加、无关以及拮抗等联合作用,对反硝化作用各反应过程、微生物多样性以及反硝化功能基因产生不同于单一抗生素暴露条件下的抑制作用. 因此,通过研究抗生素联合作用效果,可以进一步了解抗生素对硝酸盐氮去除的影响.
由于常规模拟试验花费时间长且复杂多变,通过药敏试验可快速的获得抗生素复合对反硝化细菌的影响. 目前,药敏试验的主要方法有纸片扩散法和微量肉汤稀释法,纸片扩散法从定性角度通过测定抑菌圈直径大小及抑菌图形报告解释抗生素的敏感性及联合抑菌效果,微量肉汤稀释法则通过确定最低抑菌浓度(minimal inhibitory concentration, MIC),并以部分抑菌浓度指数(fractional inhibitory concentration index,FICI)法从定量角度对药物联合作用效果进行评价[7]. 张玉叶等选取氟喹诺酮类5种典型抗生素,通过纸片扩散法与微量肉汤稀释进行药敏试验解释了复合条件下的联合抑菌效应,可能由于抗生素的浓度效应以及两种方法结果解释机理的不同,导致两种方法分别确定的抗生素的联合作用结果存在不一致性[8],为回答此问题并准确确定复合抗生素对反硝化细菌的联合抑菌效应,本文选取5大类抗生素中7种典型的抗生素,通过两两复合探讨对于确定抗生素联合抑菌效应存在的问题及解决方案,以期为复合抗生素对水土环境中反硝化作用影响研究方法的选择和结果的确定提供参考.
抗生素联合对反硝化细菌作用效果的确定方法
Method for determining the effect of antibiotic combination on denitrifying bacteria
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摘要: 抗生素在地下水环境中被频繁检出,其对硝酸盐降解的反硝化作用产生不同程度影响已被多项研究证实,多种不同功能的抗生素联合作用越来越受到关注. 本研究选取甘度反硝化细菌进行单一及联合药敏试验,探究了反硝化菌对喹诺酮类、四环素类、磺胺类、大环内酯类、林可霉素类抗生素的敏感性及抗生素的联合抑菌效果,对确定联合作用的方法进行了讨论. 结果表明,微量肉汤稀释法与纸片扩散法测得反硝化细菌对单一抗生素的敏感性具有一致性,敏感性大小主要与抗生素的种类有关. 在抗生素联合作用的试验中,纸片扩散法抑菌图形报告存在结果依赖于两圆盘之间的距离的问题,而微量肉汤稀释法存在结果解释方法及部分抑菌指数(FIC)标准不统一的问题. 以棋盘法的实验结果为基础,通过比较单一与复合抗生素各孔中微生物差异确定抗生素作用关系,优化了微量肉汤稀释法. 此外,进一步提出了微生物量测定法,解决了抗生素浓度设定的局限性问题. 新方法通过拟合微生物生长曲线,可以更直观、更准确地解释复合抗生素之间的关系. 本研究结果可为复合抗生素对水土环境中反硝化作用影响研究方法的选择和结果的确定提供参考.Abstract: Antibiotics are frequently detected in the groundwater environment, and their effects on the denitrification of nitrate degradation have been confirmed by a number of studies. The combined effect of antibiotics with different functions have been paid more and more attention. In this study, glycan denitrifying bacteria were selected for single and combined drug sensitivity tests, The sensitivities of denitrifying bacteria to quinolones, tetracycline, sulfonamides, macrolides and lincomycin antibiotics and the combined effects of antibiotics were investigated, and the method for determining the combined effect was discussed. The results showed that the sensitivities of denitrifying bacteria to a single antibiotic measured by the micro broth dilution method and the disc diffusion method were consistent, and the sensitivity was mainly related to the type of antibiotic. In determination of combined effects of antibiotics, the antibacterial graphic report of the disc diffusion method has the problem that the results were dependent distances between the two drug-sensitive discs, and the micro broth dilution method has the problem of inconsistence between result interpretation method and partial antibacterial index (FIC) standards. Based on the experimental results of the checkerboard method, the effects of antibiotics were determined by comparing the microbial differences in each hole of single and combined antibiotics and the micro broth dilution method was optimized. Furthermore, a microbial biomass determination method was proposed, which solved the limitation of antibiotic concentration setting. The new method can more intuitively and accurately explain the relationship of combined antibiotics by fitting the microbial growth curve. The findings obtained in this study can provide a reference for the selection of research methods and the determination of results for the impact of compound antibiotics on denitrification in the water and soil environment.
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表 1 药敏纸片药物含量
Table 1. Drug content of drug-sensitive paper
抗菌药物
Antibacterial drugsERY TCY CLI SMX ENR OFL CIP 每片药物含量/μg 25 25 25 25 5 5 5 表 2 纸片扩散法联合药敏试验结果
Table 2. The results of the disk-diffusion method combined with the drug susceptibility test
组别
Group抗生素组合A+B
Antibiotic combination A+B联合效果
Combined effect药物A
Drug A抑菌圈直径/mm
Antimicrobial circle diameter药物B
Drug B抑菌圈直径/mm
Antimicrobial circle diameter1# CIP 20 ENR 24 拮抗作用 2# CIP 21 OFL 19 拮抗作用 3# ENR 24 TCY 16 拮抗作用 4# CIP 19 TCY 13 拮抗作用 5# ENR 25 OFL 18 拮抗作用 6# ENR 25 ERY 13 无关作用 7# CIP 22 ERY 11 无关作用 8# OFL 18 ERY 12 无关作用 9# OFL 21 TCY 18 无关作用 10# ERY 12 TCY 17 累加作用 表 3 不同解释方法之间复合抗生素作用结果的差异
Table 3. Difference in the results of combined antibiotic action between different explanatory methods
组别
Group药物A+B
Drug A+BMethod 1 Method 2 Method 3 Method 4 FIC 作用结果
Effect resultFIC 作用结果
Effect resultFIC 作用结果
Effect resultFIC 作用结果
Effect result1# CIP+ENR 2.8 拮抗作用 1.25 无关作用 8 拮抗作用 NA 累加/无关作用 2# CIP+OFL 2.8 拮抗作用 1.25 无关作用 8 拮抗作用 NA 拮抗作用 3# ENR+OFL 2.1 拮抗作用 1.25 无关作用 8 拮抗作用 NA 累加/无关作用 4# CIP+TCY 0.64 累加作用 0.38 协同作用 1 累加作用 NA 协同作用 5# ERY+TCY 0.79 累加作用 0.5 协同作用 1.5 无关作用 NA 协同作用 6# OFL+ERY 0.99 累加作用 0.5 协同作用 2 无关作用 NA 协同作用 7# ENR+ERY 1.45 无关作用 0.56 累加作用 4 拮抗作用 NA 累加/无关作用 8# CIP+ERY 0.95 无关作用 0.31 协同作用 3 无关作用 NA 协同作用 9# OFL+TCY 1.56 无关作用 0.75 累加作用 5 拮抗作用 NA 累加/无关作用 10# ENR+TCY 1.13 无关作用 0.38 协同作用 2.5 拮抗作用 NA 协同作用 表 4 纸片扩散法与微量肉汤稀释法联合药敏试验结果比较
Table 4. Comparison of drug sensitivity test results between disc diffusion method and broth dilution method
组别
Group药物A
Drug A药物B
Drug B纸片扩散法
disk-diffusion method微量肉汤稀释法 Microbroth dilution method 方法一
Method 1方法二
Method 2方法三
Method 3方法四
Method 41# CIP ENR 拮抗作用 拮抗作用 无关作用 拮抗作用 累加/无关作用 2# CIP OFL 拮抗作用 拮抗作用 无关作用 拮抗作用 拮抗作用 3# ENR OFL 拮抗作用 拮抗作用 无关作用 拮抗作用 累加/无关作用 4# CIP TCY 拮抗作用 累加作用 协同作用 累加作用 协同作用 5# ERY TCY 拮抗作用 累加作用 协同作用 无关作用 协同作用 6# OFL ERY 无关作用 累加作用 协同作用 无关作用 协同作用 7# ENR ERY 无关作用 无关作用 累加作用 拮抗作用 累加/无关作用 8# CIP ERY 无关作用 无关作用 协同作用 无关作用 协同作用 9# OFL TCY 无关作用 无关作用 累加作用 拮抗作用 累加/无关作用 10# ENR TCY 累加作用 无关作用 协同作用 拮抗作用 协同作用 表 5 生长曲线拟合相关参数
Table 5. Growth curve fitting related parameters
单一体系
Single systemNm λ μm 复合体系
Composite systemNm λ μm 相关作用
Related effects3.9063 μg∙L−1 ENR 1.6 4.27 0.352 3.9063 μg∙L−1 ENR+15.625 μg∙L−1 OFL 1.43 6.21 0.425 协同作用 7.8125 μg∙L−1 ENR 1.57 4.37 0.343 15.625 μg∙L−1 OFL+4 mg∙L−1 ERY 1.55 3.02 0.283 无关作用 15.625 μg∙L−1 OFL 1.6 4.39 0.355 7.8125 μg∙L−1 ENR+31.25 μg∙L−1 OFL 1.18 2.14 0.232 累加作用 31.25 μg∙L−1 OFL 1.33 4.88 0.318 3.90625 μg∙L−1 ENR+62.5 μg∙L−1 OFL 0.42 8.74 0.422 协同作用 62.5 μg∙L−1 OFL 0.94 7.58 0.375 7.8125 μg∙L−1 ENR+4 mg∙L−1 ERY 1.52 3.80 0.296 无关作用 4 mg∙L−1ERY 1.5 2.16 0.253 3.90625 μg∙L−1 ENR+4 mg∙L−1 ERY 1.47 2.00 0.251 累加作用 表 6 100 ng∙L−1抗生素浓度联合作用结果
Table 6. Results of combined action of 100 ng∙L−1 antibiotic concentration
组别
Group药物A/(Abs)
Drug A药物B/(Abs)
Drug BA+B/(Abs)
Drug A+B作用结果
Effect result1# CIP 1.595 ENR 1.514 1.545 无关作用 2# CIP 1.595 ERY 1.540 1.568 无关作用 3# ENR 1.514 OFL 1.568 1.553 无关作用 4# CIP 1.595 OFL 1.568 1.582 无关作用 5# OFL 1.568 ERY 1.540 1.542 无关作用 6# OFL 1.568 TCY 1.525 1.545 无关作用 7# ERY 1.540 TCY 1.525 1.415 累加作用 8# ENR 1.514 TCY 1.525 1.445 累加作用 9# CIP 1.595 TCY 1.525 1.779 拮抗作用 10# ENR 1.514 ERY 1.540 1.555 拮抗作用 表 7 生长曲线拟合相关参数
Table 7. Growth curve fitting related parameters
ENR TCY ERY ENR+TCY ERY+TCY Nm 1.751 1.888 1.763 1.279 1.13 λ −10.26 −10.17 −9.07 2.589 1.642 μm 0.141 0.136 0.151 0.171 0.198 -
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