First three Escherichia coli isolates harbouring mcr-1 in Uruguay

Abstract

Objective: This report described the first Escherichia coli (E. coli) isolates harbouring mcr-1 in Uruguay.

Methods: Three E. coli isolates were obtained from blood, urine and rectal swabs from different patients in two hospitals. Extended-spectrum β-lactamases (ESBL), plasmid-encoded (pAmpC) β-lactamases, plasmid-mediated quinolone resistance (PMQR) genes, class 1 integrons, and mcr-1, mcr-2 and mcr-3 were sought and characterised in three E. coli isolates. Transfer of resistance determinants was assessed by conjugation. Clonality was analysed by multilocus sequence typing.

Results: All isolates were categorised as being colistin-resistant and the mcr-1 gene was detected. Two isolates were also resistant to oxyimino cephalosporins: one on account of bla_CMY-2 and the other due to bla_CTX-M-15, the latter also harbouring transferable quinolone-resistance genes (aac(6')Ib-cr and qnrB). All mcr-1 genes were transferred by conjugation to recipient strains. The mcr-1-bearing isolates belonged to sequence types ST10, ST93 and ST5442.

Conclusions: ST10 is considered as a high-risk clone worldwide. This type of mcr-1-harbouring clone is a major concern for human and animal health and must be under close surveillance. This study detected the presence of mcr-1 for the first time in Uruguay, albeit in an allodemic manner, associated with different antibiotic-resistance genes and from diverse clinical contexts. Considering that colistin is often the last therapeutic option available for multidrug-resistant Gram-negative bacilli infections, it is important to maximise precautions to avoid dissemination of isolates carrying mcr-1.

Keywords: Colistin resistance; E. coli; IncX4; mcr-1.