AUTHOR=Wong Marcus H. , Chan Edward W. , Liu Li Z. , Chen Sheng 

TITLE=PMQR genes oqxAB and aac(6′)Ib-cr accelerate the development of fluoroquinolone resistance in Salmonella typhimurium

JOURNAL=Frontiers in Microbiology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2014.00521

DOI=10.3389/fmicb.2014.00521

ISSN=1664-302X

ABSTRACT=<p>Emergence of multidrug-resistant <italic>Salmonella typhimurium</italic> strains, especially the ACSSuT and nalidixic acid R types, has significantly compromised the effectiveness of current strategies to control <italic>Salmonella</italic> infections, resulting in increased morbidity and mortality. Clinical <italic>S. typhimurium</italic> 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 <italic>oqxAB</italic> and <italic>aac(6′)Ib-cr</italic> were encoded on plasmids of various sizes and the presence of these two elements together with a single <italic>gyrA</italic> mutation in <italic>S. typhimurium</italic> were sufficient to mediate resistance to CIP. Acquisition of the <italic>oqxAB</italic> and <italic>aac(6′)Ib-cr</italic> encoding plasmids by <italic>S. typhimurium</italic> caused a fourfold increase in CIP minimal inhibitory concentration. Furthermore, the presence of <italic>oqxAB</italic> and <italic>aac(6′)Ib-cr</italic> in <italic>Salmonella</italic> dramatically increased the mutation prevention concentration of CIP which may due to mutational changes in the drug target genes. In conclusion, possession of <italic>oqxAB</italic> and <italic>aac(6′)Ib-cr</italic> encoding plasmid facilitate the selection of CIP resistant <italic>S. typhimurium</italic>, thereby causing a remarkable increase of CIP resistance among clinical <italic>Salmonella</italic> strains in Hong Kong.</p>