Eikenella corrodens

Eikenella corrodens is a microaerophilic gram-negative rod which is a normal inhabitant of human mucosal surfaces, particularly the oral cavity. Although an uncommon cause of infection, it is by no means rare. It is found most often as part of a mixed infection, particularly with streptococci, but is capable of independently causing serious infection in both normal and immunocompromised hosts. Given its slow growth, requirement for hemin when grown aerobically, and preference for CO2 enrichment, it is likely that the involvement of Eikenella in an infection is not always recognized, and it would be prudent to alert the laboratory in situations where isolation of Eikenella is likely (especially in head and neck infections or infected wounds caused by a human bite). Although mixed infections which include Eikenella may resolve with treatment directed at the other infecting organisms, treatment of such infections with antibiotics to which Eikenella is resistant may result in a pure Eikenella infection. Such an outcome may occur, for example, when a human bite wound is treated with clindamycin or metronidazole. Among the oral antibiotics, penicillin, tetracycline, and chloramphenicol are generally effective, whereas cephalexin, dicloxacillin and their relatives are not. Cefoxitin and the third-generation cephalosporins are highly effective against Eikenella.