Fig. 2.

Diversity of the sul3 integrons based on published studies and sequences deposited in the GenBank database. In silico comparative analysis was made using BLAST and CLUSTAL softwares available at the BLAST (http://www.ncbi.nlm.nih.gov/blast//) and ClustalW2 (http://www.ebi.ac.uk/Tools/clustalw2/index.html) websites. The sul3 gene is associated with class 1 integrons that differ from class 1 sul1 integrons in the 3′ region, which comprise the gene cassette initially annotated qacH but called qacI afterward in order to distinguish it from the unrelated qacH gene of Staphylococcus aureus (GenBank accession no. AF205943) (20, 22). ^a, the first described sul3 platform recovered from an E. coli swine isolate in Switzerland in 2002 (GenBank accession no. AJ459418); ^b, orf1 is also annotated as yqkA-yusZ or orfA-orfB (GenBank accession no. AY509004, EU219534, FM242710, FM244708, FM244709, FM244710, FM244712, and FM244713); ^c, insertions of IS10 or IS26 within IS440-sul3 were found in some isolates (GenBank accession no. FJ587511, HQ875013, and HQ875016) (Fig. 1); ^d, the orf1-mefB sequence was absent or not determined; ^e, the presence of sequences upstream of intI1 or downstream of tniC was not determined or was absent; ^f, mefB is absent or truncated. aadA2 corresponding to FM242710 is a hybrid of aadA1a and aadA2 containing attC_aadA1a. It is annotated aadA2 in the GenBank database.