Spread of ST274 Clone in Different Niches: Resistome, Virulome, and Phylogenetic Relationship

ST274 is an international epidemic high-risk clone, mostly associated with hospital settings and appears to colonize cystic fibrosis (CF) patients worldwide. To understand the relevant mechanisms for its success, the biological and genomic characteristics of 11 ST274- strains from clinical and non-clinical origins were analyzed. The extensively drug-resistant (XDR/DTR), the non-susceptible to at least one agent (modR), and the -truncated (by IS) strains showed a chronic infection phenotype characterized by loss of serotype-specific antigenicity and low motility. Furthermore, the XDR/DTR and modR strains presented low pigment production and biofilm formation, which were very high in the -truncated strain. Their whole genome sequences were compared with other 14 ST274- genomes available in the NCBI database, and certain associations have been primarily detected: and genes, serotype O:3, / genotype, group V of type IV pili, and pyoverdine locus class II. Other general molecular markers highlight the absence of and / genes and the presence of the same mutational pattern in genes involving two-component sensor-regulator systems PmrAB and CreBD, exotoxin A, quorum-sensing RhlI, beta-lactamase expression regulator AmpD, PBP1A, or FusA2 elongation factor G. The proportionated ST274- results could serve as the basis for more specific studies focused on better antibiotic stewardship and new therapeutic developments.