Abstract
Sequence type 59 (ST59) is the dominant type of community-associated methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Previously, we reported that ST59 MRSA harbors enterococcal IS1216V-mediated multidrug-resistant composite transposons MESPM1 or MES6272-2. The MES were found to have a mosaic structure, largely originating in enterococci and partly native to S. aureus. The current study aimed to track the origin of the MES and how they disseminated from enterococci to ST59 S. aureus. A total of 270 enterococcal isolates were analyzed, showing that two ST64 Enterococcus faecalis isolated in 1992 and 11 clonal complex 17 Enterococcus faecium harbored MESPM1-like and MES6272-2-like structures, respectively. Sequence analysis revealed that ST64 E. faecalis strain N48 acquired the MESPM1-like structure on the plasmid pEflis48. The pEflis48 harbored the enterococci-originated region (erythromycin, kanamycin, and streptomycin resistances) and the S. aureus-originated region (chloramphenicol resistance) of MESPM1 but was separated by the replication region of the plasmid. Homologous recombination between the two direct repeats of IS1216V resulted in excision of the replication region of the plasmid to regenerate MESPM1. The p4780-1 and pV19 of E. faecium carried MES6272-2-like structures with IS1216V, albeit with multiple insertions by other insertion sequences. The findings show that IS1216V plays important roles in bidirectional gene transfer of multidrug resistance between enterococci and S. aureus.
Highlights
Sequence type 59 (ST59) methicillin-resistant Staphylococcus aureus (MRSA) is the dominant type of community-associated MRSA (CA-MRSA) in Taiwan and can be divided into two clones: Panton–Valentine leukocidin (PVL)-positive/staphylococcal cassette chromosome mec (SCCmec) V and PVL-negative/SCCmec IV [1,2,3]
IS1216V is an enterococcal insertion sequence rarely found in S. aureus, up to five copies of IS1216V are located in MESPM1 and MES6272-2 of ST59 S. aureus [6]
We described MESPM1 and MES6272-2 in ST59 MRSA, the novel multidrug-resistant composite transposons mediated by enterococcal IS1216V and mingled with S. aureus- and enterococci-originated sequences [4,5]
Summary
Sequence type 59 (ST59) methicillin-resistant Staphylococcus aureus (MRSA) is the dominant type of community-associated MRSA (CA-MRSA) in Taiwan and can be divided into two clones: Panton–Valentine leukocidin (PVL)-positive/staphylococcal cassette chromosome mec (SCCmec) V and PVL-negative/SCCmec IV [1,2,3]. We reported that ST59 S. aureus acquires IS1216V-mediated enterococcal composite transposons MES, which are responsible for multidrug resistance [4,5]. ST59 PVL-positive/SCCmec V MRSA acquires MESPM1, which confers resistances to erythromycin, kanamycin, streptomycin, and chloramphenicol; ST59 PVL-negative/SCCmec IV MRSA usually acquires MES6272-2, which confers resistances to erythromycin, kanamycin, gentamicin, and chloramphenicol. Both the MESPM1 and MES6272-2 are inserted into the chromosomal sasK gene with an 8 bp att sequence and are flanked by direct repeats of IS1216V at both ends, indicating that MESPM1 and MES6272-2 are composite transposons mediated by IS1216V [4,5]. IS1216V is an enterococcal insertion sequence rarely found in S. aureus, up to five copies of IS1216V are located in MESPM1 and MES6272-2 of ST59 S. aureus [6]
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