Description of novel resistance islands coding blaCTX-M-2 in IncC type 2 plasmids.

Abstract

OBJECTIVES\nWe sequenced two IncA/C plasmids harbouring blaCTX-M-2 in Klebsiella pneumoniae clinical isolates and compared their antibiotic resistance islands.\n\n\nMETHODS\nTransconjugants were obtained from two clinical K. pneumoniae isolates harbouring blaCTX-M-2. Plasmid DNA from transconjugants underwent short-read whole-genome sequencing, reads were assembled, and gaps were closed by PCR and sequencing. Determination of plasmid replicons, antibiotic resistance genes, identification and characterization of insertion sequence elements and comparisons with publicly available plasmid sequences were performed.\n\n\nRESULTS\nblaCTX-M-2 was located in a complex class 1 integron In35::ISCR1::blaCTX-M-2, inserted in two different transposons designated Tn7057 and Tn7058, that reside in the resistance islands of pUR-KP0923 and pUR-KP1025 plasmids, respectively. The general modules of both transposons were: In35::ISCR1::blaCTX-M-2-Tn1000-like-Tn2*-ISKpn11-12-13 variable module-ΔTn21. In Tn7057 there were ΔIS10R-catA2 associated with an additional ISKpn13. Both plasmids belonged to IncC type 2 ST3. pUR-KP0923 was 167,138 bp in length and had a 37,926 bp resistance island at position 4 (RI-4). Plasmid pUR-KP1025 was 168,128 bp with a RI-4 of 36,222 bp.\n\n\nCONCLUSION\nThis report describes the molecular nature of two transposons, designated Tn7057 and Tn7058, harbouring blaCTX-M-2, that reside in IncC type 2 and ST3 plasmids. These transposons mediate resistance to oxyimino cephalosporins, gentamicin and, in the case of Tn7057, to chloramphenicol. CTX-M-2 is an important ESBL to South American epidemiology. It is remarkable that, despite being only two plasmid sequences, the information exposed here could contribute to the better understanding of the resistance islands from IncC type 2 plasmids.