Rapid diagnosis of enterohemorrhagic Escherichia coli O157:H7 directly from fecal specimens using immunofluorescence stain.
Serotype O157:H7 is most frequently encountered among verotoxin-producing Escherichia coli. Most laboratories use MacConkey-sorbitol agar as a screening medium. Presumptive identification of sorbitol-negative colonies is then accomplished by latex agglutination or biochemical tests with serologic confirmation, which requires 18-36 hours for completion. This study attempted to detect E coli O157:H7 directly from stool specimens by direct immunofluorescence (DIF) antibody staining to provide quicker turnaround (< 2 hours). A total of 336 abnormal fecal samples (bloody, watery, semi-liquid, or mucoid) were examined by this method. Results were compared with those of culture. Direct immunofluorescence antibody staining of the direct fecal smear detected all isolates of E coli O157 that were recovered by culture, including nonmotile strains, strains possessing the H7 flagellar antigen, and one strain with a flagellar antigen other than H7. Optimum results were achieved when specimens were pretreated with 5% bleach and centrifugation. No false-negative results were obtained with bleach-pretreated stool samples.
Park
C H
CH
Department of Pathology, Fairfax Hospital, Falls Church, VA 22046.
Hixon
D L
DL
Morrison
W L
WL
Cook
C B
CB
D001431:Bacteriological Techniques; D002648:Child; D002675:Child, Preschool; D004751:Enteritis / Q000175:diagnosis*; D004926:Escherichia coli / Q000145:classification / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000175:diagnosis*; D005243:Feces / Q000382:microbiology*; D005455:Fluorescent Antibody Technique; D006471:Gastrointestinal Hemorrhage / Q000382:microbiology*; D006801:Humans; D007223:Infant; D013997:Time Factors