Tohoku Research Station, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, 31 Uminai, Shichinohe, Kamikita, Aomori 039-2586, Japan.
Vet Microbiol. 2012 Mar 23;155(2-4):444-7. doi: 10.1016/j.vetmic.2011.09.033. Epub 2011 Oct 7.
The aim of this study was to analyse a florfenicol-resistant Mannheimia haemolytica isolated from a calf to determine the genetic basis of its florfenicol-resistance. The antimicrobial susceptibility and plasmid content of the isolate were determined. A florfenicol resistant plasmid carrying the floR gene was identified by PCR and transformed into Escherichia coli JM109 and HB101 strains. The plasmid was then mapped and sequenced completely. The isolate was resistant to chloramphenicol, florfenicol, oxytetracycline, kanamycin, dihydrostreptomycin, nalidixic acid, ampicillin, and amoxicillin; it carried a floR plasmid of 7.7kb, designated pMH1405. The mobilisation and replication genes of pMH1405 showed extensive similarity to the 5.1-kb pDN1 plasmid from Dichelobacter nodosus and the 10.8-kb pCCK381 plasmid from Pasteurella multocida. An adjacent 2.4-kb segment was highly homologous to the TnfloR region of the E. coli BN10660 plasmid. A plasmid-mediated floR gene was responsible for florfenicol resistance in the bovine respiratory tract pathogen M. haemolytica. The pMH1405 plasmid is the smallest floR-carrying plasmid reported to date. To the best of our knowledge, this is the first report of a florfenicol-resistant gene in M. haemolytica.
本研究旨在分析一株从犊牛中分离到的对氟苯尼考耐药的溶血曼海姆菌，以确定其氟苯尼考耐药的遗传基础。测定了分离株的抗菌药物敏感性和质粒含量。通过 PCR 鉴定出携带 floR 基因的氟苯尼考耐药质粒，并将其转化至大肠杆菌 JM109 和 HB101 菌株中。然后对质粒进行了完全图谱绘制和测序。该分离株对氯霉素、氟苯尼考、土霉素、卡那霉素、二氢链霉素、萘啶酸、氨苄西林和阿莫西林耐药；携带一个 7.7kb 的 floR 质粒，命名为 pMH1405。pMH1405 的移动和复制基因与来自 Dichelobacter nodosus 的 5.1kb pDN1 质粒和来自 Pasteurella multocida 的 10.8kb pCCK381 质粒具有广泛的相似性。一个相邻的 2.4kb 片段与大肠杆菌 BN10660 质粒的 TnfloR 区域高度同源。一个质粒介导的 floR 基因导致了牛呼吸道病原体曼海姆溶血杆菌对氟苯尼考的耐药性。pMH1405 质粒是迄今为止报道的最小的携带 floR 基因的质粒。据我们所知，这是曼海姆溶血杆菌中首次报道氟苯尼考耐药基因。
