title: Isolation of Shiga toxin-producing Escherichia coli from fresh produce using STEC heart infusion washed blood agar with mitomycin-C.
abstract: The ability to detect and isolate Shiga toxin-producing Escherichia coli (STEC) remains a major challenge for food microbiologists. Although methods based on nucleic acids and antibodies have improved detection of STECs in foods, isolation of these bacteria remains arduous.  STEC isolation is necessary for matching food, environmental, and clinical isolates during outbreak investigations and for distinguishing between pathogenic and nonpathogenic organisms. STEC heart infusion washed blood agar with mitomycin-C (SHIBAM) is a modification of washed sheep blood  agar prepared by adding mitomycin-C and optimizing both the washed blood and base agar to better isolate STECs. Most STEC isolates produce a zone of hemolysis on SHIBAM plates and are easily distinguishable from background microbiota. Here, we present data supporting the use of SHIBAM to isolate  STECs from fresh produce. SHIBAM was tested for accuracy in identifying STECs (365 of 410 STEC strains were hemolytic, and 63 of 73 E. coli strains that did not produce Shiga toxin were not hemolytic) and for recovery from artificially inoculated fresh produce (11 of 24 romaine lettuce  samples and 6 of 24 tomato samples). STEC recovery with SHIBAM agar was greatly improved when compared with recovery on Levine's eosin-methylene blue agar as a reference method.
authors.affiliation: U.S. Food and Drug Administration, San Francisco District, Alameda, CA 94502, USA. andrew.lin@fda.hhs.gov
authors.forename: Andrew
authors.initials: A
authors.lastname: Lin
authors.forename: Lam
authors.initials: L
authors.lastname: Nguyen
authors.forename: Laurie M
authors.initials: LM
authors.lastname: Clotilde
authors.forename: Julie A
authors.initials: JA
authors.lastname: Kase
authors.forename: Insook
authors.initials: I
authors.lastname: Son
authors.forename: Carol R
authors.initials: CR
authors.lastname: Lauzon
mesh_terms: D000362:Agar; D001769:Blood; D015169:Colony Count, Microbial / Q000379:methods*; D003470:Culture Media; D005506:Food Contamination / Q000032:analysis*; D006801:Humans; D016685:Mitomycin / Q000494:pharmacology; D012680:Sensitivity and Specificity; D022603:Shiga Toxins / Q000096:biosynthesis; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification* / Q000378:metabolism; D014675:Vegetables / Q000382:microbiology*
chemical_list: D003470:Culture Media; D022603:Shiga Toxins; D016685:Mitomycin; D000362:Agar