A simple and rapid cultural method for detection of Enterobacter sakazakii in environmental samples |
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Authors: | Guillaume-Gentil O Sonnard V Kandhai M C Marugg J D Joosten H |
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Affiliation: | Nestlé Research Centre, Quality and Safety Department, CH-1000 Lausanne 26, Switzerland. olivier.guillaume-gentil@rdls.nestle.com |
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Abstract: | A method was developed to detect and identify Enterobacter sakazakii in environmental samples. The method is based on selective enrichment at 45+/-0.5 degrees C in lauryl sulfate tryptose broth supplemented with 0.5 M NaCl and 10 mg/liter vancomycin (mLST) for 22 to 24 h followed by streaking on tryptone soy agar with bile salts. When exposed to light during incubation at 37 degrees C, E. sakazakii produces yellow colonies within 24 h; identification was confirmed by testing for alpha-glucosidase activity and by using API 20E strips. All of the E. sakazakii strains tested (n = 99) were able to grow in mLST at 45+/-0.5 degrees C, whereas 35 of 39 strains of potential competitors, all belonging to the Enterobacteriaceae, were suppressed. A survey was carried out with 192 environmental samples from four different milk powder factories. Using this new protocol, E. sakazakii was isolated from almost 40% of the samples, whereas the reference procedure (enrichment in buffered peptone water, isolation on violet red bile glucose agar, and biochemical identification of randomly chosen colonies) only yielded 26% positive results. This selective method can be very useful for the rapid and reliable detection of E. sakazakii in environmental samples. |
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