AUTHOR=Li Shu-Min , Zhou Yu-Feng , Li Liang , Fang Liang-Xing , Duan Jia-Hong , Liu Fan-Rui , Liang Hua-Qing , Wu Yu-Ting , Gu Wei-Qi , Liao Xiao-Ping , Sun Jian , Xiong Yan-Qiong , Liu Ya-Hong 

TITLE=Characterization of the Multi-Drug Resistance Gene cfr in Methicillin-Resistant Staphylococcus aureus (MRSA) Strains Isolated From Animals and Humans in China

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.02925

DOI=10.3389/fmicb.2018.02925

ISSN=1664-302X

ABSTRACT=<p>We investigated <italic>cfr</italic>-positive and -negative MRSA strains isolated from animals and humans in different geographical areas of China, from 2011 to 2016. Twenty <italic>cfr</italic>-positive strains (15.6%) were identified from 128 MRSA strains including 17 from food animals and three from humans. The resistance rates and prevalence of the tested antibiotic resistance genes (ARGs) in the <italic>cfr</italic>-positive MRSA isolates were higher than that in the <italic>cfr</italic>-negative MRSA isolates. All <italic>cfr</italic>-positive MRSA isolates were co-carrying <italic>fexA</italic> and <italic>ermC</italic>, and had significantly higher <italic>optrA</italic> incidence rate vs. the <italic>cfr</italic>-negative isolates (<italic>P</italic> &lt; 0.05). In addition, multilocus sequence typing (MLST) assays showed that ST9 and <italic>spa</italic>-type t899 were the most prevalent ST and <italic>spa</italic> types in the study strains. However, all of the 20 <italic>cfr</italic>-positive and 10 randomly selected <italic>cfr</italic>-negative MRSA isolates were clonally unrelated as determined by pulsed-field gel electrophoresis (PFGE) analyses. Importantly, the <italic>cfr</italic> gene was successfully transferred to a recipient <italic>Staphylococcus aureus</italic> strain RN4220 from 13 of the 20 <italic>cfr</italic>-positive MRSA isolates by electroporation. Among these 13 <italic>cfr</italic>-positive MRSA isolates, two different genetic contexts surrounding <italic>cfr</italic> were determined and each was associated with one type of <italic>cfr</italic>-carrying plasmids. Of note, the predominant genetic context of <italic>cfr</italic> was found to be a Tn<italic>558</italic> variant and locate on large plasmids (∼50 kb) co-harboring <italic>fexA</italic> in 11 of the 13 MRSA isolates. Furthermore, the <italic>cfr</italic> gene was also identified on small plasmids (∼ 7.1 kb) that co-carried <italic>ermC</italic> in two of the 13 MRSA isolates. Our results demonstrated a high occurrence of multi-drug resistance in <italic>cfr</italic>-positive MRSA isolates, and the spread of <italic>cfr</italic> might be attributed to horizontal dissemination of similar <italic>cfr</italic>-carrying transposons and plasmids.</p>