Kim Ahran, Lim Yunjin, Kim Nameun, Luan Nguyen Thanh, Roh Heyong Jin, Park Chan-Il, Han Hyun-Ja, Jung Sung-Hee, Cho Mi-Young, Kim Do-Hyung, Smith Peter
1 Department of Aquatic Life Medicine, College of Fisheries Science, Pukyong National University , Busan, Republic of Korea.
2 Department of Marine Biology & Aquaculture, College of Marine Science, Gyeongsang National University , Tongyeong, Republic of Korea.
Microb Drug Resist. 2018 Oct;24(8):1226-1235. doi: 10.1089/mdr.2017.0137. Epub 2018 Feb 13.
In a study of 39 isolates of Edwardsiella piscicida made from Korean aquaculture sites, sul genes were detected in 16 isolates and dfr genes in 19. Ten isolates were shown to contain both sul and dfr genes. MIC and disc diffusion zones assays were performed to measure the phenotypic susceptibilities of the 39 isolates. Normalized resistance interpretation was applied to these data to categorize isolates as either fully susceptible or as manifesting reduced susceptibility. The standard CLSI protocols specify the use of a mixture of sulfamethoxazole/trimethoprim (20:1) in both MIC and disc diffusion tests. Using the CLSI MIC protocol, 100% of the isolates containing dfr genes, but only 75% of the isolates containing sul genes, were categorized as manifesting reduced susceptibility. Using the CLSI disc diffusion protocol, only 58% of the isolates containing dfr genes and 69% of those containing sul genes were categorized as manifesting reduced susceptibility. When the single agent trimethoprim was substituted for the combined mixture in both the MIC and disc diffusion protocols, 100% of the dfr-positive isolates were categorized as NWT. When the single-agent sulfamethoxazole was substituted, the analysis of the MIC characterized 100% and the disc zone data 94% of the sul-positive isolates as manifesting reduced susceptibility. It is argued that the use of trimethoprim and sulfamethoxazole as single agents in phenotypic susceptibility tests would provide more meaningful data than the currently recommended use of these two agents combined.
在一项对从韩国水产养殖场所分离出的39株杀鲑气单胞菌爱德华氏菌进行的研究中，在16株中检测到了磺胺类基因，19株中检测到了二氢叶酸还原酶（dfr）基因。有10株同时含有磺胺类和dfr基因。对这39株菌株进行了最低抑菌浓度（MIC）和纸片扩散法试验，以测定其表型敏感性。对这些数据应用标准化抗性解释，将菌株分类为完全敏感或表现出敏感性降低。临床和实验室标准协会（CLSI）的标准方案规定在MIC和纸片扩散试验中均使用磺胺甲恶唑/甲氧苄啶（20:1）混合物。使用CLSI的MIC方案，含有dfr基因的菌株中有100%被归类为表现出敏感性降低，但含有磺胺类基因的菌株中只有75%被如此归类。使用CLSI的纸片扩散方案时，含有dfr基因的菌株中只有58%、含有磺胺类基因的菌株中只有69%被归类为表现出敏感性降低。当在MIC和纸片扩散方案中用单药甲氧苄啶替代联合混合物时，100%的dfr阳性菌株被归类为非野生型（NWT）。当用单药磺胺甲恶唑替代时，MIC分析将100%的磺胺类阳性菌株、纸片扩散数据将94%的此类菌株归类为表现出敏感性降低。有人认为，在表型敏感性试验中使用甲氧苄啶和磺胺甲恶唑作为单药将比目前推荐的联合使用这两种药物提供更有意义的数据。
