Focusing on Infections: Distribution, Antimicrobial Susceptibilities and Phylogeny.

The immunosuppression conditions and the presence of medical devices in patients favor the infections. However, the features of this aerobic actinomycete have been little explored. Strains ( = 164) were characterized with 16S rDNA and A1 genes to define their phylogenetic relationships, and subjected to broth microdilution to profile the antimicrobial susceptibilities of species that caused infections in Spain during the 2005-2021 period. Four out of the eleven identified species were responsible for 86.0% of the infections: (53.0%), (18.3%), (8.5%) and (6.1%). Respiratory tract infections (61.6%) and bacteremia (21.9%) were the most common infections. The A1 gene resolved the inconclusive identification, and two major clonal lineages were observed for and . Species showed a wide antimicrobial susceptibility profile. Cefoxitin resistance varies depending on the species, reaching 94.2% for and 36.0% for . What is noteworthy is the minocycline resistance in (11.5%), the clarithromycin resistance in A1 lineage II (30.0%) and the amoxicillin-clavulanate and cefepime resistance in (21.4% and 42.8%, respectively). and stand out as the prevalent species causing infections in Spain. Resistance against cefoxitin and other antimicrobials should be considered.