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

Abstract

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 bla CTX-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 bla OXA-1 and bla TEM-1 genes were detected in eight and ten strains, respectively. In addition, bla SHV-1, bla SHV-11 and bla SHV-27 were found in six, one and one K. pneumoniae strains, respectively. The new variant bla SHV-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 bla CTX-M-15, bla TEM-1b and bla OXA-1 genes was demonstrated from three K. pneumoniae to E. coli. IS Ecp1 and orf477 were located upstream and downstream, respectively, of the bla CTX-M-15 gene in 10 strains. The occurrence of the bla CTX-M-15 gene in unrelated strains might have originated from the dissemination of mobile genetic elements in which IS Ecp1 may have played an important role.