Genomic Background and Phylogeny of A-Positive Strains Resistant to Meropenem-EDTA.

BACKGROUND

shows high antimicrobial resistance (AMR) rates and possesses numerous AMR mechanisms. Its carbapenem-resistant strains (metallo-β-lactamase A-positive) appear as an emergent, evolving clade.

METHODS

This work examines the genomes, taxonomy, and phylogenetic relationships with respect to other genomes of two strains (CNM20180471 and CNM20200206) resistant to meropenem+EDTA and other antimicrobial agents.

RESULTS

Both strains possessed A genes (A14b and the new A28), along with other AMR mechanisms. The presence of other efflux-pump genes, AB/JK/XY-M, EF/EF-C, and especially R, which reduces the entry of carbapenem via the repression of porin OprD, may be related to meropenem-EDTA resistance. None of the detected insertion sequences were located upstream of A. The genomes of these and other strains that clustered together in phylogenetic analyses did not meet the condition of >95% average nucleotide/amino acid identity, or >70% in silico genome-to-genome hybridization similarity, to be deemed members of the same species, although <1% difference in the genomic G+C content was seen with respect to the reference genome NCTC 9343T.

CONCLUSIONS

Carbapenem-resistant strains may be considered a distinct clonal entity, and their surveillance is recommended given the ease with which they appear to acquire AMR.