Description of novel resistance islands harbouring bla(CTX-M-2) in IncC type 2 plasmids

Objectives: We sequenced two IncA/C plasmids harbouring bla(CTX-M-2) in Klebsiella pneumoniae clinical isolates and compared their antibiotic resistance islands. Methods: Transconjugants were obtained from two clinical K. pneumoniae isolates harbouring bla(CTX-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 characterisation of insertion sequence (IS) elements, and comparison with publicly available plasmid sequences were performed. Results: bla(CTX-M-2) was located in a complex class 1 integron In35::ISCR1::bla(CTX-M-2), inserted in two different transposons designated Tn7057 and Tn7058, that reside in the resistance islands of plasmids pUR-KP0923 and pUR-KP1025, respectively. The general modules of both transposons were In35::ISCR1::bla(CTX-M-2) -Tn1000-like-Tn2*- ISKpn11-12-13 variable module-Delta Tn21. In Tn7057 there was Delta IS10R-catA2 associated with an additional ISKpn13. Both plasmids belonged to IncC type 2 and 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. Conclusion: This report describes the molecular nature of two transposons (Tn7057 and Tn7058) harbouring bla(CTX-M-2) that reside in IncC type 2 ST3 plasmids. These transposons mediate resistance to oxyimino-cephalosporins, gentamicin and, in the case of Tn 7057, chloramphenicol. CTX-M-2 is an important extended-spectrum beta-lactamase (ESBL) to South American epidemiology. It is remarkable that despite being only two plasmid sequences, the information revealed here could contribute to a better understanding of the resistance islands from IncC type 2 plasmids. (C) 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy.