Yaqoob Muhammad, Wang Li Ping, Kashif Jam, Memon Javed, Umar Sajid, Iqbal Muhammad Farooq, Fiaz Muhammad, Lu Cheng-Ping
Department of Veterinary Medicine, Nanjing Agricultural University, Nanjing, People's Republic of China.
Faculty of Veterinary and Animal Sciences, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan.
Folia Microbiol (Praha). 2018 Jul;63(4):443-449. doi: 10.1007/s12223-017-0579-7. Epub 2018 Jan 6.
The genetic basis for phenicol resistance was examined in 38 phenicol-resistant clinical Escherichia coli isolates from poultry. Out of 62 isolates, 38 showed resistance for chloramphenicol and nine for florfenicol, respectively. Each strain also demonstrated resistance to a variety of other antibiotics. Molecular detection revealed that the incidence rates of the cat1, cat2, flo, flo-R, cmlA, and cmlB were 32, 29, 18, 13, 0, and 0%, respectively. Nineteen strains were tolerant to organic solvents. PCR amplification of the complete acrR (regulator/repressor) gene of five isolates revealed the amino acid changes in four isolates. DNA sequencing showed the non-synonymous mutations which change the amino acid, silent mutation, and nucleotide deletion in four isolates. MY09C10 showed neither deletion nor mutation in nucleotide. The AcrA protein of the AcrAB multidrug efflux pump was overexpressed in these strains. Complementation with a plasmid-borne wild-type acrR gene reduced the expression level of AcrA protein in the mutants and partially restored antibiotic susceptibility one- to fourfold. This study shows that mutations in acrR are an additional genetic basis for phenicol resistance.
对38株来自家禽的耐氯霉素临床大肠杆菌分离株的氯霉素耐药基因基础进行了研究。在62株分离株中，分别有38株对氯霉素耐药，9株对氟苯尼考耐药。每株菌株还对多种其他抗生素耐药。分子检测显示，cat1、cat2、flo、flo-R、cmlA和cmlB的发生率分别为32%、29%、18%、13%、0和0%。19株菌株对有机溶剂耐受。对5株分离株的完整acrR（调节/抑制）基因进行PCR扩增，发现4株分离株存在氨基酸变化。DNA测序显示4株分离株存在改变氨基酸的非同义突变、沉默突变和核苷酸缺失。MY09C10在核苷酸水平上既无缺失也无突变。AcrAB多药外排泵的AcrA蛋白在这些菌株中过表达。用质粒携带的野生型acrR基因进行互补可降低突变体中AcrA蛋白的表达水平，并使抗生素敏感性部分恢复1至4倍。本研究表明，acrR突变是氯霉素耐药的另一个遗传基础。
