The immunohistological diagnosis of E. coli O157:H7 colitis: possible association with colonic ischemia.
OBJECTIVE
E. coli O157:H7 may cause hemorrhagic colitis resembling ischemic colitis. Diagnosis is usually made by finding sorbitol-negative colonies on MacConkey agar that react with O157 and H7 antisera. Most ischemic colitis is idiopathic, but some may be caused by E. coli O157:H7, inasmuch as this organism can produce fibrin thrombi in colon vasculature. The objectives of this study were to determine whether E. coli O157:H7 infection can be diagnosed retrospectively from paraffin blocks of colon sections and whether an association exists between E. coli O157:H7 infection and colonic ischemia.


METHODS
Paraffin-embedded sections of normal colon (n = 2) and various colitides [ischemic (n = 11), E. coli O157:H7 (n = 2), IBD (n = 8) and pseudomembranous (n = 3)] were used. Sections were deparaffinized, rehydrated, incubated with 3% peroxide in methanol, rinsed, and incubated with peroxidase-labeled antibody isolated from goats immunized with whole E. coli O157:H7. Sections were stained with peroxidase chromagen reagent and counterstained with hematoxylin. Coarse, granular, orange-brown staining was considered positive. To determine the localization of the chromagen deposits, three cases that stained positive, including one of the culture-proved E. coli O157:H7 colitis and two of colonic ischemia, were processed for electron microscopy.


RESULTS
Both cases (100%) of E. coli O157:H7 colitis and three of 11 (27.3%) cases of ischemic colitis stained positive by light microscopy. In one culture-proved case, electron microscopy demonstrated staining of bacillary structures; in two cases of colonic ischemia, extensive deposits of chromagen material were present that were associated neither with inflammatory cells nor with bacterial forms.


CONCLUSIONS
Immunoperoxidase staining of archival sections may be used to diagnose E. coli O157:H7 infection. An etiological role for this organism is possible in some cases of colonic ischemia.
Department of Medicine, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, New York 10467, USA.
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Su
L J
LJ
Brandt
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Sigal
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Alt
J J
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Steinberg
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K
Patterson
P I
PI
Tarr
D000368:Aged; D000907:Antibodies, Bacterial; D002863:Chromogenic Compounds; D003092:Colitis / Q000382:microbiology* / Q000473:pathology; D017091:Colitis, Ischemic / Q000382:microbiology / Q000473:pathology*; D003106:Colon / Q000033:anatomy & histology / Q000098:blood supply; D004396:Coloring Agents; D004761:Enterocolitis, Pseudomembranous / Q000473:pathology; D004927:Escherichia coli Infections / Q000175:diagnosis / Q000473:pathology*; D019453:Escherichia coli O157 / Q000276:immunology / Q000302:isolation & purification / Q000648:ultrastructure; D005260:Female; D005337:Fibrin; D006471:Gastrointestinal Hemorrhage / Q000382:microbiology / Q000473:pathology; D006416:Hematoxylin; D006801:Humans; D007124:Immunoenzyme Techniques; D015212:Inflammatory Bowel Diseases / Q000473:pathology; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D016612:Paraffin Embedding; D012189:Retrospective Studies; D013927:Thrombosis / Q000382:microbiology
D000907:Antibodies, Bacterial; D002863:Chromogenic Compounds; D004396:Coloring Agents; D005337:Fibrin; D006416:Hematoxylin