BACKGROUND: Kerstersia gyiorum is a Gram-negative bacillus of the Alcaligeneceae family, first
isolated in 2003. It has been ever since increasingly commonly isolated from human samples and is
associated with chronic ear infections and chronic cutaneous lower limbs infections. We report a case
of chronic suppurative otitis media, a disease representing a great health burden, involving this
emerging pathogen.
CASE PRESENTATION: We present the case of a 23-year-old homeless woman that came to the
Lausanne university hospital with a complaint of purulent discharge and a strong pain in the left ear
for the past five weeks. The patient was known for having ear problem since childhood. A chronic
suppurative otitis media with cholesteatoma and cophosis of the left ear was diagnosed a few months
ago. The patient was treated with amoxicillin/clavulanic acid and topical ciprofloxacin. In addition, she
underwent a surgery for exeresis of cholesteatoma and an inflammatory polyp that was filling the
middle ear, with favorable outcome. The microbiological analysis of the granulomatous tissues
revealed the presence of K. gyiorum and Fusobacterium necrophorum. Susceptibility testing of the
Kerstersia strain showed resistance to ciprofloxacin, according to the EUCAST criteria. We completed
this case report with a genomic analysis of this strain of K. gyiorum, that allowed us to identify several
virulence genes such as iron uptake systems, various enzymes and the operon encoding flagellar
system and three antimicrobial resistance genes.
CONCLUSION: With this case report, genomic analysis and literature review, we highlight the
pathogenic potential of K. gyiorum and raise awareness about the resistance of several strains to
ciprofloxacin, the molecule of choice for the treatment of chronic suppurative otitis media.