A simple and rapid cultural method for detection of Enterobacter sakazakii in environmental samples

• Published in: Journal of food protection Vol. 68; no. 1; pp. 64 - 69
• Main Authors: GUILLAUME-GENTIL, O, SONNARD, V, KANDHAI, M. C, MARUGG, J. D, JOOSTEN, H
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association of Milk, Food and Environmental Sanitarians 2005
• Subjects: alpha-Glucosidases - analysis; Biological and medical sciences; Colony Count, Microbial - methods; Cronobacter sakazakii - classification; Cronobacter sakazakii - isolation & purification; Culture Media - chemistry; Enterobacter sakazakii; Enterobacteriaceae; Environmental Microbiology; Environmental Monitoring - methods; food; Food Contamination - analysis; Food industries; Food Microbiology; Fundamental and applied biological sciences. Psychology; General aspects; Humans; infant formula; infections; Meningitis, Bacterial - etiology; Meningitis, Bacterial - prevention & control; Methods of analysis, processing and quality control, regulation, standards; neonatal meningitis; powdered milk; Reproducibility of Results; Sensitivity and Specificity; Species Specificity; system; Temperature; Time Factors; Enterobacter; Analysis method; Sample; Bacteria; Control method; Detection; Enterobacteriaceae
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-68.1.64

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.