磺胺类耐药菌中抗性基因sul的表达规律

Expression Patterns of sul Genes in Sulfonamide-Resistant Bacteria

抗生素环境污染是影响抗生素抗性基因传播和扩散的主要因素,然而关于抗生素耐药菌在抗生素暴露下抗性基因的表达机制研究甚少。本研究利用RT-PCR方法检测了土壤中优势耐药菌菌株炭疽芽孢杆菌(Bacillus anthracis SYN201,G+)和弗氏志贺菌菌株(Shigella flexneri NJJN802,G-)在含有不同浓度磺胺类药物的培养基中生长不同时间后抗性基因(sul 1、sul 2、sul 3)的表达变化。结果发现:无论培养基中是否存在磺胺类药物,菌株SYN201和NJJN802中的3种磺胺类抗性基因均分别在培养的第72小时或36小时出现一个明显的表达峰,而在其他培养时间下不表达或表达量处于相对极低的水平;磺胺嘧啶的存在有助于提高菌株在此特征表达时间下抗性基因的表达水平,与未加磺胺嘧啶组相比,暴露于磺胺嘧啶(60μg·m L^(-1))组的sul 1、sul 2和sul 3在菌株SYN201中的相对表达量分别提高了2.5、4.8和3.2倍,而在菌株NJJN802中的相对表达量分别提高了3.7、6.0和5.0倍。通过将耐药菌暴露于不同磺胺嘧啶浓度下考察sul基因相对表达情况,研究发现随着培养基中磺胺嘧啶浓度的升高(0~1 024μg·m L^(-1)),菌株SYN201和NJJN802中sul基因的表达量整体上呈现出明显的上升趋势。本研究对揭示磺胺耐药菌的抗性表达规律及抗生素暴露对其抗性表达发挥的作用具有重要意义。

Antibiotic pollution is the key factor for the transport and spread of antibiotic resistance genes （ARGs）. However, there were few reports on the expression mechanism of ARGs in antibiotic resistant bacteria （ARBs） un- der the exposure of antibiotics. The different expression of sul genes were detected by RT-PCR respectively in Ba- cillus anthracis （SYN201, G＋） and Shigella Hexneti （NJJN802, G） at different times and different sulfadiazine con- centrations. It is found that the mRNA levels of sul genes in strain SYN201 and NJJ＇N802 reached climax at 72 h and 36 h respectively regardless of exposure to sulfadiazine, whereas they did not express, or express at a relatively low level at other times. The presence of sulfadiazine was helpful to improve the expression level of resistance gene at 72 h for SYN201 and 36 h for NJJN802. Compared with the group without sulfadiazine, the relative expression of sull, su12 and sub in strain SYN201 exposed to 60 μg.mL-1 sulfadiazine increased as 2.5, 4.8 and 3.2 times, and that in NJJN802 increased as 3.7, 6.0 and 5.0 times. When investigating the relative expression level of sul genes in the resistant strains under the exposure to different concentrations of sulfonamides, we found that the ex- pression levels of sul genes in the resistant strains SYN201 and NJJN802 increased as the exposure concentrations of sulfonamides （0-1 024 μg.mL-1） increased. This study will shed light on the expression characteristics of ARGs of sulfadiazine-resistant bacteria and the role of antibiotic exposure in the expression of ARGs.