title: Diagnostic properties of three conventional selective plating media for selection of Bacillus cereus, B. thuringiensis and B. weihenstephanensis.
abstract: The aim of this study was to assess the diagnostic properties of the two selective plating media and a chromogenic medium for identification of Bacillus cereus. The 324 isolates were B. cereus (37%), Bacillus weihenstephanensis (45%) or Bacillus thuringiensis (18%), as identified by a new combination of techniques. All isolates were growing on mannitol-egg yolk-polymyxin agar (MYP), and they did not form acid from mannitol. However, a significant lower number of B. thuringiensis isolates did not show lecithinase activity. All isolates were also growing on polymyxin-egg yolk-mannitol-bromothymol blue agar (PEMBA); however, 11% isolates indicated that they did produce acid from mannitol, and 15% isolates did not show any lecithinase activity. Five of the isolates did not grow at all on the chromogenic agar, and 14 of the growing isolates were β-glucosidase negative. It is concluded that the two recommended selective plating media MYP and PEMBA for detection of B. cereus group bacteria both have their limitations for identification of some B. cereus, B. weihenstephanensis or B. thuringiensis. However, MYP is preferable compared to PEMBA. The chromogenic medium has its own advantages and limitations, and some of the limitations seem to be solved by incubation at 30°C instead of the recommended 37°C.
authors.affiliation: Department of Environmental Science, Aarhus University, P.O. Box 358, Frederiksborgvej 399, 4000 Roskilde, Denmark. nbh@dmu.dk
authors.forename: Niels Bohse
authors.initials: NB
authors.lastname: Hendriksen
authors.forename: Bjarne Munk
authors.initials: BM
authors.lastname: Hansen
mesh_terms: D000818:Animals; D001181:Arthropods / Q000382:microbiology; D001407:Bacillus / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D001409:Bacillus cereus / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D001413:Bacillus thuringiensis / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D015169:Colony Count, Microbial / Q000379:methods*; D003470:Culture Media / Q000378:metabolism*; D005516:Food Microbiology; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology; D006801:Humans; D012988:Soil Microbiology
chemical_list: D003470:Culture Media
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