Characterization of the first blaCTX-M-14/ermB-carrying Inch plasmid from Latin America

Azithromycin represents a valid therapeutic option for gastrointestinal and systemic infections caused by multidrug resistant (MDR) diarrheagenic Escherichia coli, Shigella and Salmonella species. However, acquired macrolide resistance in these species has been increasingly described, mostly related to macrolide modifying enzymes encoded by mph- and erm-type genes. In this study, we characterized the first bla(CTX-M-14)/ermB-carrying Inch plasmid from Latin America, which was detected in a MDR E. coli clinical isolate from Uruguay. Plasmid pUR-EC07 was a 105,836-bp Inch ST80 plasmid harboring bla(CTX-M-14),bla(TEM-1) and ermB, and characterized by a backbone region of 92,554 bp, and a multi resistance region (MRR) of 13,282 bp, bounded by two directly-oriented 1526 elements, and inserted upstream of ResD. The MRR comprised two nested 1826 composite transposons (Tn6651 and Tn6652). Tn6651 included the ermBL-ermB operon flanked by two 1526 copies in opposite direction. Tn6652 included bla(TEM-), with an upstream remnant of a Tn3-family transposon, and bla(CTX-M-14), located in a genetic context consisting of ISEcp1 Delta-IS10-bla(CTX-M-14)-IS903D. To the best of our knowledge, pUR-EC07 represents the first Inch plasmid harboring ermB and bla(CTX-M-14) described in Latin America. Given the wide dissemination of Inch-type plasmids in Salmonella enterica, an important concern is represented by the potential transfer of similar plasmids to strains resistant to ciprofloxacin, which would result in the loss of the three main therapeutic resources.