title: PMQR genes oqxAB and aac(6')Ib-cr accelerate the development of fluoroquinolone resistance in Salmonella typhimurium.
abstract: Emergence of multidrug-resistant Salmonella typhimurium strains, especially the ACSSuT and nalidixic acid R types, has significantly compromised the effectiveness of current strategies to control Salmonella infections, resulting in increased morbidity and mortality. Clinical S. typhimurium isolates recovered in Hong Kong during the period of 2005-2011 were increasingly resistant to ciprofloxacin (CIP) and antibiotics of the ACSSuT group. Our data revealed that oqxAB and aac(6')Ib-cr were encoded on plasmids of various sizes and the presence of these two elements together with a single gyrA mutation in S. typhimurium were sufficient to mediate resistance to CIP. Acquisition of the oqxAB and aac(6')Ib-cr encoding plasmids by S. typhimurium caused a fourfold increase in CIP minimal inhibitory concentration. Furthermore, the presence of oqxAB and aac(6')Ib-cr in Salmonella dramatically increased the mutation prevention concentration of CIP which may due to mutational changes in the drug target genes. In conclusion, possession of oqxAB and aac(6')Ib-cr encoding plasmid facilitate the selection of CIP resistant S. typhimurium, thereby causing a remarkable increase of CIP resistance among clinical Salmonella strains in Hong Kong.
authors.affiliation: Food Safety and Technology Research Centre, Hong Kong Polytechnic University - Shenzhen Research Institute Shenzhen, China ; State Key Laboratory of Chirosciences, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University Kowloon, China.
authors.forename: Marcus H
authors.initials: MH
authors.lastname: Wong
authors.affiliation: Department of Microbiology, The Prince of Wales Hospital - The Chinese University of Hong Kong Shatin, China.
authors.forename: Edward W
authors.initials: EW
authors.lastname: Chan
authors.affiliation: Food Safety and Technology Research Centre, Hong Kong Polytechnic University - Shenzhen Research Institute Shenzhen, China ; State Key Laboratory of Chirosciences, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University Kowloon, China.
authors.forename: Li Z
authors.initials: LZ
authors.lastname: Liu
authors.affiliation: Food Safety and Technology Research Centre, Hong Kong Polytechnic University - Shenzhen Research Institute Shenzhen, China ; State Key Laboratory of Chirosciences, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University Kowloon, China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Chen
keywords: ACSSuT R type; S. typhimurium; aac(6′)Ib-cr; ciprofloxacin resistance; oqxAB