Eikenella

Taxobox
name = "Eikenella"
regnum = Bacteria
phylum = Proteobacteria
classis = Beta Proteobacteria
ordo = Neisseriales
familia = Neisseriaceae
genus = "Eikenella"

"Eikenella corrodens" is a fastidious Gram-negative facultative anaerobic bacillus. It was first identified by M. Eiken in 1958, who called it "Bacteroides corrodens". [cite journal | author=Eiken M | year=1958 | title=Studies on an anaerobic, rod-shaped, gram-negative microorganism: "Bacteroides corrodens" N. sp. | journal=Acta Pathol Microbiol Scand | volume=43 | pages=404–16 ]

Microbiology

"E. corrodens" is a pleomorphic bacillus that sometimes appears coccobacillary and typically creates a depression (or "pit") in the agar on which it is growing. It grows in aerobic and anaerobic conditions, but requires an atmosphere enhanced by 3–10% carbon dioxide. The colonies are small and greyish, they produce a greenish discoloration of the underlying agar and smell faintly of bleach (hypochlorite). Only half produce the pitting of the agar that is considered characteristic. They are oxidase-positive, catalase-negative, urease-negative, indole-negative and reduce nitrate to nitrite.

Medical importance

"E. corrodens" is a commensal of the human mouth and upper respiratory tract. It is an unusual cause of infection and when it is cultured, it is most usually found mixed with other organisms. Infections most commonly occur in patients with cancers of the head and neck, [cite journal | author=Sheng WS, Hsueh PR, Hung CC, "et al." | title=Clinical features of patients with invasive "Eikenella corrodens" infections and microbiological characteristics of the causative isolates | journal=Eur J Clin Microbiol Infect Dis | year=2001 | volume=20 | pages=231–36 | doi=10.1007/s100960100477 ] but it is also common in human bite infections, especially "reverse bite" or "fight bite", or "clenched fist injuries". [cite journal | author=Goldstein EJC. | title=Bite wounds and infections | journal=Clin Infect Dis | volume=14 | year=1992 | 633–40 ] It also causes infections in insulin-dependent diabetics and intravenous drug users who lick their needles. [cite journal | author=Swisher LA, Roberts JR, Glynn MJ. | title=Needle licker's osteomyelitis | journal=Am J Emerg Med | year=1994 | volume=12 | pages=343–36 | doi=10.1016/0735-6757(94)90156-2 ] It is one of the HACEK group of infections which are a cause of culture-negative endocarditis.

"E. corrodens" infections are typically indolent (the infection does not become clinically evident until a week or more after the injury). They also mimic anaerobic infection in being extremely foul-smelling.

Treatment

"E. corrodens" can be treated with penicillins, cephalosporins or tetracyclines. It is innately resistant to macrolides (e.g., erythromycin), clindamycin and metronidazole. It is susceptible to fluoroquinolones (e.g., ciprofloxacin) "in vitro" but there is no clinical evidence available to advocate its use in these infections.

ee also

HACEK organism

References