AUTHOR=Zhang Feng , Wu Shi , Huang Jiahui , Yang Runshi , Zhang Jumei , Lei Tao , Dai Jingsha , Ding Yu , Xue Liang , Wang Juan , Chen Moutong , Wu Qingping 

TITLE=Presence and Characterization of a Novel cfr-Carrying Tn558 Transposon Derivative in Staphylococcus delphini Isolated From Retail Food

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.598990

DOI=10.3389/fmicb.2020.598990

ISSN=1664-302X

ABSTRACT=<p>Antimicrobial resistance has become a major public health threat. Food-related <italic>Staphylococcus</italic> species have received much attention due to their multidrug resistance. The <italic>cfr</italic> gene associated with multidrug resistance has been consistently detected in food-derived <italic>Staphylococcus</italic> species. In this retrospective study, we examined the prevalence of <italic>cfr</italic>-positive <italic>Staphylococcus</italic> strains isolated from poultry meat in different geographical areas of China from 2011 to 2016. Two <italic>cfr</italic>-positive <italic>Staphylococcus delphini</italic> strains were identified from poultry meat in China. Comparative and whole-genome analyses were performed to characterize the genetic features and overall antimicrobial resistance genes in the two <italic>S. delphini</italic> isolates 245-1 and 2794-1. Whole-genome sequencing showed that they both harbored a novel 20,258-bp <italic>cfr</italic>-carrying Tn<italic>558</italic> transposon derivative on their chromosomes. The Tn<italic>558</italic> derivative harbors multiple antimicrobial resistance genes, including the transferable multiresistance gene <italic>cfr</italic>, chloramphenicol resistance gene <italic>fexA</italic>, aminoglycoside resistance genes <italic>aacA-aphD</italic> and <italic>aadD</italic>, and bleomycin resistance gene <italic>ble</italic>. Surprisingly, within the Tn<italic>558</italic> derivative, an active unconventional circularizable structure containing various resistance genes and a copy of a direct repeat sequence was identified by two-step PCR. Furthermore, core genome phylogenetic analysis revealed that the <italic>cfr</italic>-positive <italic>S. delphini</italic> strains were most closely related to <italic>S. delphini</italic> 14S03313-1 isolated from Japan in 2017 and 14S03319-1 isolated from Switzerland in 2017. This study is the first report of <italic>S. delphini</italic> harboring a novel <italic>cfr</italic>-carrying Tn558 derivative isolated from retail food. This finding raises further concerns regarding the potential threat to food safety and public health safety. The occurrence and dissemination of similar <italic>cfr</italic>-carrying transposons from diverse <italic>Staphylococcus</italic> species need further surveillance.</p>