Eikenella Corrodens in Tonsillar Infections

Eikenella corrodens (E. corrodens) is a Gram-negative facultative anaerobic bacillus that originally was thought to be an attenuated and indigenous bacterium. In this study, we investigated the clinical and bacteriological characteristics of E. corrodens infections of the tonsil. Seventeen consecutive patients treated in our department for E. corrodens infections of the tonsils were retrospectively analyzed. Microbial specimens were subjected to light microscopic examination, aerobic culture using chocolate and sheep blood agar media, and anaerobic culture using Brucella HK agar medium. Cultured bacteria were subjected to antimicrobial susceptibility tests using the broth microdilution method. The patients were 11 males and 6 females, ranging in age from 4 to 53 years with an average of 22.8 years. One patient had liver cirrhosis, while the other patients had no particular risk factors or underlying diseases. E. corrodens was detected from the surface of the tonsil in 4 cases, from the resected tonsillar tissue in 11 cases, and from pus in the abscesses in 2 cases. Twelve patients demonstrated polymicrobial infections. Streptococcus was the most frequently detected pathogen coexisting with E. corrodens. Isolated E. corrodens was susceptible to third-generation cephems, carbapenems, and new quinolones; and moderately susceptible to benzylpenicillin, ampicillin, cefotiam, and minocycline; but resistant to first-generation cephems, oxacillin, erythromycin, and clindamycin. In conclusion, E. corrodens infections of the tonsils are not rare even in hosts with normal immunity. We should be aware of this bacteria in tonsillar infections.