Tracking blaCTX-M transmission through transposable elements in uropathogenic and commensal E. coli

To investigate the nucleotide sequences associated with transposable elements carrying blaCTX-M allelic variants as potential markers for the transmission of antimicrobial resistance genes between domestic animals, humans and the environment. We conducted whole-genome sequencing and analyzed the nucleotide sequences of most abundant blaCTX-M allelic variants (blaCTX-M-27, blaCTX-M-55, and blaCTX-M-65) in commensal Escherichia coli (n = 20) from household members in Quito and uropathogenic E. coli (UPEC) (n = 149) isolated from nine clinics in Quito, Ecuador. The Ecuadorian commensal E. coli and UPEC displayed identical nucleotide sequences surrounding the blaCTX-M gene and the synteny was similar to those found in other parts of the world; however phylogenetic analysis indicated that the genetic environments in Ecuadorian isolates were unique. These findings suggest that the nucleotide sequences flanking the blaCTX-M genes may be useful for resolving ARG transmission pathways, especially inter-regional analyses. Bacteria can share small bits of DNA with each other using a type of DNA vehicle, known as a plasmid. The intestinal bacteria of domestic animals can also spread to humans. Some of these bacteria may share genes with human bacteria that make them resistant to antibiotics. It is hard to know how many of these genes move from animal to human bacteria because they are linked to pieces of DNA that let them jump around inside bacteria. This makes it harder to track how resistance genes spread. This study looks at one type of resistance gene called blaCTX-M which makes bacteria resistant to antibiotics called cephalosporins, used to treat serious infections. We found that the DNA around this gene was the same in bacteria from both humans and domestic animals in Quito, Ecuador. However, the DNA was different from what is found in other parts of the world. We suggest that this DNA near the blaCTX-M gene could help us understand how antibiotic resistance spreads between animals and humans in different regions.