Klebsiella oxytocaas a Causative Organism of Antibiotic-Associated Hemorrhagic Colitis

Enterotoxicity of a nonribosomal peptide causes antibiotic-associated colitis

“…Key features of AAHC upon endoscopy are segmental mucosal hemorrhage and mucosal edema affecting mainly the ascending colon and cecum (14,40). Histology typically resembles that of colitis induced by toxin-producing bacteria.…”

“…Animals with a conventional microbiota restricted for opportunistic pathogens were chosen, as opposed to germ-free animals, to simulate the antibiotic-induced dysbiosis experienced by colitis patients taking penicillins. Combined therapy of penicillin with a nonsteroidal anti-inflammatory drug (NSAID) increases risk for development of AAHC (14,40), and thus we included indometacin in the medication control. Mice were treated intraperitoneally with the penicillin derivative amoxicillin/clavulanate and s.c. with the NSAID indometacin.…”

“…Antibiotic clearance of a niche in the colon facilitates overgrowth of K. oxytoca (10 7 cfu/g feces during acute phases of AAHC compared with 10 2 cfu/g feces in healthy subjects) (15). Our earlier work showed that the dysbiotic population shift dominated by K. oxytoca causes colitis (14), thereby identifying the resident organism as a pathobiont (17).…”

“…This bacterium is a resident of the gut in 2-10% of healthy individuals (13)(14)(15). In AAHC, a brief therapy with penicillins triggers dysbiosis with sudden onset of bloody diarrhea and abdominal cramps (14). K. oxytoca constitutively expresses resistance to amino-and carboxypenicillins (16).…”

Enterotoxigenic Bacteroides fragilis: A potential instigator of colitis

“…Mice were maintained under specific pathogen-free conditions and studied according to protocols approved by the Johns Hopkins University Animal Care and Use Committee in accordance with the Association for the Assessment and Accreditation of Laboratory Animal Care International. For most experiments, similar to other mouse models of enteric infection, 19 mice were pretreated for 5 days with 5 g/L of streptomycin (Sigma) and 100 mg/L of clindamycin (Pharmacia, Kalamazoo, MI) in their drinking water; antibiotics at the same dose were continued until the day of sacrifice. The goal of this protocol was to enhance colonization with B. fragilis and to permit ready isolation and quantification of inoculated bacteria.…”