亚胺培南对铜绿假单胞菌敏感和耐药菌株DNA释放的影响

目的：观察亚胺培南对铜绿假单胞菌标准菌株和耐药菌株体外培养释放DNA的影响。方法：选择铜绿假单胞菌的标准菌株和临床分离耐药菌株作为实验菌株，检测其亚胺培南的最低抑菌浓度（MIC），琼脂糖凝胶电泳法观察不同浓度亚胺培南作用下铜绿假单胞菌的DNA释放情况，并用Quantity One软件分析所释放DNA片段的分子量和含量。结果：亚胺培南作用下铜绿假单胞菌从1／2MIC开始释放小片段DNA，大于1／2MIC仅释放l条大片段DNA，且含量少，等于1／2MIC可释放3条DNA，但无小片段DNA，小于1／2MIC可释放4．5条DNA，且含量多。1／16MIC时，标准菌株释放的第1、5条DNA片段含量偏少，3、4条DNA片段含量偏多，而耐药菌株相反。耐药菌株与标准菌株相比释放的DNA片段有所不同，耐药菌株比标准菌株多释放一条DNA片段（第2条），分子量为2784bp，耐药菌株的第1、3、4、5条DNA片段分子量均比标准菌株小。耐药菌株释放的第3、4、5条DNA含量明显高于标准菌株，P〈0．01，其统计有显著学意义。结论：不同亚胺培南浓度作用下，铜绿假单胞菌会释放不同片段大小和含量的DNA分子，耐药菌株与标准菌株释放的DNA片段数量和含量有明显差异，其与耐药机制的关系值得进一步研究。

The Release of DNA from Pseudomonas Aeruginosa in Vitro during Treatment with Imipenem

Objective： To investigate the release of DNA from standard strain and drug-resistant strain of Pseudomonas aeruginosa in vitro during treatment with imipenem. Methods： Standard strain and clinical drug-resistant strain of Pseudomonas aemginosa were used as test strains, and their minimum inhibitory concentrations （MIC） of imipenem were detected. The release phenomena of the bacte- rial DNA were detected by the agarose gel electrophoresis, and the relative molecular mass and content of DNA fragment were statistically analyzed by software Quantity one. Results： When the concentrations of imipenem were less than or equal to 1/2 MIC, both strains of Pseudomonas aeruginosa released 3-5 DNA fragments. When the concentrations of imipenem were greater than 1/2 MIC, only one large fragment of DNA was released with a low content. Imipenem with MIC caused both strains to release 3 fragments of DNA, but smallest fragment of DNA was absent. When Imipenem was less than the 1/2 MIC, Pseudomonas aeruginosa released 4-5 DNA fragments with high content. When the concentration ofimipenem was 1/16 MIC, standard strain released a few No 1 and 5 DNA fragments and more No 3 and 4 DNA fragments but phenomenon in resistant strain was contrary. Compared with standard strain, resistant strain released an additional 2784 bp DNA fragment （No 2 DNA fragment）. The relative molecular weights of No 3, 4, 5 DNA fragments from resistant strain were slightly smaller than those of standard strain. Their content were significantly higher than those of the standard strain （P〈0. 01）. Conclusion： After treated by imipenem with different concentrations in vitro, Pseudomonas aeruginosa released different fragments of DNA with various sizes and content. This is also occurred between the drug-resistant strain and standard strain of Pseudomonas aerug- inosa. The phenomenon might probably be related to bacterial resistance mechanisms, and is worthy of further study.