Lin Dachuan, Chen Kaichao, Wai-Chi Chan Edward, Chen Sheng
Food Safety and Technology Research Center, Hong Kong PolyU Shenzhen Research Institute, Shenzhen, P. R. China.
State Key Lab of Chirosciences, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR.
Sci Rep. 2015 Oct 5;5:14754. doi: 10.1038/srep14754.
Fluoroquinolone resistance in Salmonella has become increasingly prevalent in recent years. To probe the molecular basis of this phenomenon, the genetic and phenotypic features of fluoroquinolone resistant Salmonella strains isolated from food samples were characterized. Among the 82 Salmonella strains tested, resistance rate of the three front line antibiotics of ceftriaxone, ciprofloxacin and azithromycin was 10%, 39% and 25% respectively, which is significantly higher than that reported in other countries. Ciprofloxacin resistant strains typically exhibited cross-resistance to multiple antibiotics including ceftriaxone, primarily due to the presence of multiple PMQR genes and the blaCTX-M-65, blaCTX-M-55 blaCMY-2 and blaCMY-72 elements. The prevalence rate of the oqxAB and aac(6')-Ib-cr genes were 91% and 75% respectively, followed by qnrS (66%), qnrB (16%) and qnrD (3%). The most common PMQR combination observable was aac(6')-Ib-cr-oqxAB-qnrS2, which accounted for 50% of the ciprofloxacin resistant strains. Interestingly, such isolates contained either no target mutations or only a single gyrA mutation. Conjugation and hybridization experiments suggested that most PMQR genes were located either in the chromosome or a non-transferrable plasmid. To summarize, findings in this work suggested that PMQRs greatly facilitate development of fluoroquinolone resistance in Salmonella by abolishing the requirement of target gene mutations.
近年来，沙门氏菌对氟喹诺酮类药物的耐药性日益普遍。为探究这一现象的分子基础，对从食品样本中分离出的耐氟喹诺酮类沙门氏菌菌株的遗传和表型特征进行了表征。在测试的82株沙门氏菌菌株中，头孢曲松、环丙沙星和阿奇霉素这三种一线抗生素的耐药率分别为10%、39%和25%，显著高于其他国家的报道。耐环丙沙星菌株通常对包括头孢曲松在内的多种抗生素表现出交叉耐药性，主要是由于存在多个质粒介导的喹诺酮类耐药（PMQR）基因以及blaCTX-M-65、blaCTX-M-55、blaCMY-2和blaCMY-72元件。oqxAB和aac(6')-Ib-cr基因的流行率分别为91%和75%，其次是qnrS（66%）、qnrB（16%）和qnrD（3%）。最常见的可观察到的PMQR组合是aac(6')-Ib-cr-oqxAB-qnrS2，占耐环丙沙星菌株的50%。有趣的是，此类分离株要么没有靶基因突变，要么只有单个gyrA突变。接合和杂交实验表明，大多数PMQR基因位于染色体或不可转移的质粒上。总之，这项工作的结果表明，PMQR通过消除对靶基因突变的需求，极大地促进了沙门氏菌对氟喹诺酮类药物耐药性的发展。
