Klebsiella oxytoca (K oxytoca) is a rare cause of infectious colitis. Only a handful of cases of K oxytoca colitis are described, all from France 1. Benoit R Dorval D Loulergue J Bacq Y Oliver J.M Audurier A et al. Post-antibiotic diarrheas: role of Klebsiella oxytoca. Gastroenterol Clin Biol. 1992; 16 ([French with English abstract]): 860-864 PubMed Google Scholar , 2. Bellaiche G Le Pennec M Choudat L Ley G Slama J.L Value of rectosigmoidoscopy with bacteriological culture of colonic biopsies in the diagnosis of post-antibiotic hemorrhagic colitis related to Klebsiella oxytoca. Gastroenterol Clin Biol. 1997; 21 ([French with English abstract]): 764-767 PubMed Google Scholar , 3. Beaugerie L Metz M Barbut F Bellaiche G Bouhnik Y Raskine L et al. Klebsiella oxytoca as an agent of antibiotic-associated hemorrhagic colitis. Clin Gastroenterol Hepatol. 2003; 1: 370-376 Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar , 4. 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Sakurai Y Tsuchiya H Ikegami F Funatomi T Takasu S Uchikoshi T Acute right-sided hemorrhagic colitis associated with oral administration of ampicillin. Dig Dis Sci. 1979; 24: 910-915 Crossref PubMed Scopus (67) Google Scholar , 13. Chida T Nakaya R Tsuji N Shimizu N Masuda G Seo T et al. Intestinal microflora of patients with antibiotic-associated hemorrhagic colitis associated with Klebsiella oxytoca and Clostridium difficile enterotoxin. Kansenshogaku Zasshi. 1986; 60 ([Japanese]): 608-615 PubMed Google Scholar K oxytoca is a gram-negative, facultative aerobe/anaerobe and is found in the normal fecal flora from 30% to 40% of people. Over 100 strains have been identified, a few of which produce cytotoxins that can result in an infectious colitis. The clinical presentation of K oxytoca colitis is diarrhea with mucous or blood. Prior use of a penicillin-like antibiotic is characteristic and presumably results in selection of the cytopathic strains. Other medications, such as non-steroidal anti-inflammatory drugs (NSAID), also have been implicated. Leukocytosis is common at presentation. Patients range in age from 20 to 93 years. 1. Benoit R Dorval D Loulergue J Bacq Y Oliver J.M Audurier A et al. Post-antibiotic diarrheas: role of Klebsiella oxytoca. Gastroenterol Clin Biol. 1992; 16 ([French with English abstract]): 860-864 PubMed Google Scholar The colitis is non-pseudomembranous and can be segmental, i.e., left sided or right sided, or pancolonic. 1. Benoit R Dorval D Loulergue J Bacq Y Oliver J.M Audurier A et al. Post-antibiotic diarrheas: role of Klebsiella oxytoca. Gastroenterol Clin Biol. 1992; 16 ([French with English abstract]): 860-864 PubMed Google Scholar , 2. Bellaiche G Le Pennec M Choudat L Ley G Slama J.L Value of rectosigmoidoscopy with bacteriological culture of colonic biopsies in the diagnosis of post-antibiotic hemorrhagic colitis related to Klebsiella oxytoca. Gastroenterol Clin Biol. 1997; 21 ([French with English abstract]): 764-767 PubMed Google Scholar It is characteristically of mild to moderate severity and resolves spontaneously when treatment with the inciting antibiotic is stopped. Treatment with a fluoroquinolone may be needed in select cases. This report describes the first case in which K oxytoca colitis was severe and fulminant. As well, it is the first report of the recognition of this infectious colitis in North America.