corrodens

Corrodens is a term commonly used to refer to Eikenella corrodens, a Gram-negative, non-spore-forming rod that is part of the normal human oral microbiota and can act as an opportunistic pathogen. In culture, E. corrodens forms small, translucent to pale yellow colonies and is known for a hard-to-miss “corrosion” effect on the agar, which gives the organism its name.

Morphology and growth: E. corrodens is a facultatively anaerobic, nonmotile rod. It is typically oxidase negative and grows slowly on blood-enriched media, often requiring enriched or CO2-rich conditions.

Habitat and epidemiology: It resides in the human mouth and upper respiratory tract. It is most commonly implicated in infections associated with human bites or orodental disease, including periodontal infections, endocarditis, brain abscess, and osteomyelitis. Infections are frequently polymicrobial, involving oral anaerobes and viridans streptococci.

Diagnosis: Laboratory identification relies on culture showing corroding colonies on blood agar, along with phenotypic testing and, when available, MALDI-TOF mass spectrometry or 16S rRNA sequencing. The organism is often underrecognized due to fastidious growth and its presence in mixed infections.

Treatment and prognosis: Management typically includes antibiotics active against oral flora, most commonly amoxicillin-clavulanate or ampicillin-sulbactam. Alternatives include certain cephalosporins, doxycycline, or fluoroquinolones with metronidazole; penicillin alone or clindamycin monotherapy is less reliable. With appropriate therapy, outcomes are favorable, although infections can be serious in immunocompromised patients or in endocarditis cases.