Successful Intra- but Not Inter-species Recombination of in .

Resistance acquisition natural transformation is a common process in the genus. Transformation has played an important role in the emergence of resistance to many antimicrobials in and . In a previous study, we found that currently circulating isolates of had acquired an gene that has been found to result in macrolide resistance in other bacteria but never found in species before. To determine if this resistance mechanism is transferable among species, we assessed if we could transform the gene into other commensal and pathogenic under low dose azithromycin pressure. Intraspecies recombination in commensal was confirmed with PCR and resulted in high-level macrolide resistance. Whole-genome sequencing of these transformed strains identified the complete uptake of the integration fragment. Sequence analysis showed that a large fragment of DNA (5 and 12 kb) was transferred through a single horizontal gene transfer event. Furthermore, uptake of the gene had no apparent fitness cost. Interspecies transformation of from to was, however, not successful.