title: Quantitative method for enumeration of enterotoxigenic Escherichia coli.
abstract: A rapid method was developed to quantify toxigenic Escherichia coli, using a membrane filter procedure. After filtration of samples, the membrane filter was first incubated on a medium selective for E. coli (24 h, 44 degrees C) and then transferred to tryptic soy agar (3%; 6 h, 37 degrees C). To assay for labile toxin-producing colonies, the filter was then transferred to a monolayer of Y-1 cells, the E. coli colonies were marked on the bottom of the petri dish, and the filter was removed after 15 min. The monolayer was observed for a positive rounding effect after a 15- to 24-h incubation. The method has an upper limit of detecting 30 toxigenic colonies per plate and can detect as few as one toxigenic colony per plate. A preliminary screening for these enterotoxigenic strains in polluted waters and known positive fecal samples was performed, and positive results were obtained with fecal samples only.
mesh_terms: D001431:Bacteriological Techniques; D001681:Biological Assay; D002460:Cell Line; D004768:Enterotoxins / Q000096:biosynthesis* / Q000494:pharmacology; D004926:Escherichia coli / Q000302:isolation & purification* / Q000378:metabolism; D005243:Feces / Q000382:microbiology*; D006801:Humans; D014871:Water Microbiology
chemical_list: D004768:Enterotoxins