Genetic characterisation of CTX-M-15-producing Klebsiella pneumoniae and Escherichia coli strains isolated from stem cell transplant patients in Tunisia

Characterisation of extended-spectrum β-lactamase (ESBL) genes and their genetic environments as well as the presence of integrons were analysed in nine Klebsiella pneumoniae and two Escherichia coli ESBL-positive isolates recovered in the Centre of Bone Marrow Transplantation of Tunisia. All strains harboured the blaCTX-M-15 gene and presented minimum inhibitory concentrations for cefotaxime and ceftazidime of 256–1024 mg L−1 and 16–512 mg L−1, respectively, and eight of them showed different pulsed-field gel electrophoresis patterns. The blaOXA-1 and blaTEM-1 genes were detected in eight and ten strains, respectively. In addition, blaSHV-1, blaSHV-11 and blaSHV-27 were found in six, one and one K. pneumoniae strains, respectively. The new variant blaSHV-103 was characterised in one K. pneumoniae strain. The intI1 gene was detected in eight K. pneumoniae strains and the dfrA5 + ereA2 and aadA gene cassettes were found in one and five strains, respectively. All strains harboured a 70 kb plasmid, and its transference in addition to blaCTX-M-15, blaTEM-1b and blaOXA-1 genes was demonstrated from three K. pneumoniae to E. coli. ISEcp1 and orf477 were located upstream and downstream, respectively, of the blaCTX-M-15 gene in 10 strains. The occurrence of the blaCTX-M-15 gene in unrelated strains might have originated from the dissemination of mobile genetic elements in which ISEcp1 may have played an important role.