IS <i>21-558</i> Insertion Sequences Are Involved in the Mobility of the Multiresistance Gene <i>cfr</i>

<jats:title>ABSTRACT</jats:title> <jats:p> During a study of florfenicol-resistant porcine staphylococci from Denmark, the genes <jats:italic>cfr</jats:italic> and <jats:italic>fexA</jats:italic> were detected in the chromosomal DNA or on plasmids of <jats:italic>Staphylococcus hyicus</jats:italic> , <jats:italic>Staphylococcus warneri</jats:italic> , and <jats:italic>Staphylococcus simulans</jats:italic> . A novel variant of the phenicol resistance transposon Tn <jats:italic>558</jats:italic> was detected on the ca. 43-kb plasmid pSCFS6 in <jats:italic>S. warneri</jats:italic> and <jats:italic>S. simulans</jats:italic> isolates. Sequence analysis of a 22,010-bp segment revealed that the new Tn <jats:italic>558</jats:italic> variant harbored an additional resistance gene region integrated into the <jats:italic>tnpC</jats:italic> reading frame. This resistance gene region consisted of the clindamycin exporter gene <jats:italic>lsa</jats:italic> (B) and the gene <jats:italic>cfr</jats:italic> for combined resistance to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A antibiotics bracketed by IS <jats:italic>21-558</jats:italic> insertion sequences orientated in the same direction. A 6-bp target site duplication was detected at the integration site within <jats:italic>tnpC</jats:italic> . Transpositionally active forms of the IS <jats:italic>21-558</jats:italic> element, known as minicircles, were detected by PCR and suggest that this insertion sequence is involved in the mobility of the multiresistance gene <jats:italic>cfr</jats:italic> . Based on the knowledge of the transposition pathways of IS <jats:italic>21</jats:italic> -like insertion sequences and the sequence features detected, the resistance gene region of plasmid pSCFS6 is believed to have developed via IS <jats:italic>21-558</jats:italic> -mediated cointegrate formation. The data obtained in this study identified the multiresistance gene <jats:italic>cfr</jats:italic> not only in three novel host species but also in a novel genetic context whose further analysis suggested that insertion sequences of the type IS <jats:italic>21-558</jats:italic> are likely to be involved in the dissemination of <jats:italic>cfr</jats:italic> . </jats:p>