Horizontal plasmid transfer among Klebsiella pneumoniae isolates is the key factor for dissemination of extended-spectrum β-lactamases among children in Tanzania
Increased knowledge about the role of horizontal gene transfer is key to improve our understanding of the spread of antimicrobial resistance (AMR) in human populations. We therefore studied the dissemination of the blaCTX-M-15 extended-spectrum-β-lactamase (ESBL) gene in Klebsiella pneumoniae isolates obtained from stool samples from hospitalized children and healthy controls below 2 years of age in Dar es Salaam, Tanzania, from August 2010 to July 2011.
We performed Illumina whole-genome sequencing (WGS) to characterize resistance genes, multilocus sequence type (MLST), plasmid incompatibility group (Inc), and plasmid MLST of 128 isolates of K. pneumoniae with blaCTX-M-15 recovered from both healthy and hospitalized children. We assessed the phylogenetic relationship using single nucleotide polymorphism (SNP)-based analysis and resolved the sequences of five reference plasmids by Oxford Nanopore technology to investigate plasmid dissemination.
The WGS analyses revealed the presence of a blaCTX-M-15-positive IncFIIK5/IncR plasmid with a highly conserved backbone in 70% (90/128) of the isolates. This plasmid, harboring genes encoding resistance to most β-lactams, aminoglycosides, trimethoprim-sulfamethoxazole, and chloramphenicol, was present in phylogenetically very diverse K. pneumoniae strains (48 different MLSTs) carried by both hospitalized and healthy children.
Our data strongly suggest widespread horizontal transfer of this ESBL-carrying plasmid both in hospitals and in the general population.