AUTHOR=Wang Juan , Stephan Roger , Zurfluh Katrin , Hächler Herbert , Fanning Séamus 

TITLE=Characterization of the genetic environment of blaESBL genes, integrons and toxin-antitoxin systems identified on large transferrable plasmids in multi-drug resistant Escherichia coli

JOURNAL=Frontiers in Microbiology

VOLUME=5

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2014.00716

DOI=10.3389/fmicb.2014.00716

ISSN=1664-302X

ABSTRACT=<p><bold>Objectives:</bold> Previously 14 conjugative plasmids from multi-drug resistant (MDR) <italic>Escherichia coli</italic> from healthy humans and food-producing animals in Switzerland were sequenced. The aim of this study was to extend the genetic characterization of these plasmids with a focus on <italic>bla</italic><sub>ESBL</sub> genes including <italic>bla</italic><sub>CTX-M-1</sub> and <italic>bla</italic><sub>TEM</sub>, class 1 integrons and toxin-antitoxin (TA) systems contained therein.</p><p><bold>Methods:</bold> The nucleotide sequences and subsequent annotation therein of 14 conjugative plasmids were previously determined from their corresponding transconjugants. The TA loci were confirmed by RASTA-Bacteria.</p><p><bold>Results:</bold> Eight of the conjugative plasmids identified were found to encode genes expressing ESBLs. Structural heterogeneity was noted in the regions flanking both the <italic>bla</italic><sub>CTX-M-1</sub> and <italic>bla</italic><sub>TEM</sub> genes. The <italic>bla</italic><sub>CTX-M-1</sub> genes were associated with the common insertion sequences IS<italic>Ecp1</italic> and IS<italic>26</italic>, and uniquely with an IS<italic>5</italic> element in one case; while <italic>bla</italic><sub>TEM</sub> genes were found to be associated with IS<italic>26</italic> and Tn<italic>2</italic>. A new <italic>bla</italic><sub>TEM-210</sub> gene was identified. Seven class 1 integrons were also identified and assigned into 3 groups, denoted as In54, In369 and In501. Sixteen TA loci belonging to 4 of the TA gene families (<italic>relBE</italic>, <italic>vapBC</italic>, <italic>ccd</italic> and <italic>mazEF</italic>) were identified on 11 of these plasmids.</p><p><bold>Conclusions:</bold> Comparative sequence analysis of these plasmids provided data on the structures likely to contribute to sequence diversity associated with these accessory genes, including IS<italic>26</italic>, IS<italic>Ecp1</italic> and Tn<italic>2</italic>. All of them contribute to the dissemination of the corresponding resistance genes located on the different plasmids. There appears to be no association between β-lactam encoding genes and TA systems.</p>