Janibacter hoylei

Abstract

Janibacter hoylei is a pleomorphic Gram-positive coryneform of the genus Janibacter (family Intrasporangiaceae, order Micrococcales, phylum Actinomycetota), first described in 2009 from stratospheric air samples and also recovered from soil, marine sediment, and the mosquito midgut. It is an uncommon opportunistic pathogen, most often causing sepsis in immunocompromised hosts—particularly patients with hematological malignancies, hematopoietic stem cell transplant recipients, and those at the extremes of life—typically entering through a break in skin integrity, though sepsis in immunocompetent patients, occasionally secondary to pneumonia, has also been reported. Microbiologically it is aerobic, catalase, oxidase positive, coagulase and indole negative, non-motile, non-spore-forming, alternates between bacillary and coccoid forms, and produces small, whitish-yellow, non-hemolytic colonies on blood agar. Because biochemical methods frequently misidentify it as Corynebacterium spp., definitive identification relies on MALDI-TOF with RUO libraries, 16S rRNA sequencing (complemented by rpoB), or whole-genome sequencing. No CLSI or EUCAST breakpoints exist for the genus; reported isolates show low MICs to vancomycin (treatment of choice), linezolid, imipenem, quinolones, and tetracyclines, with variable and often elevated MICs to β-lactams, especially cephalosporins.