A simple and rapid cultural method for detection of Enterobacter sakazakii in environmental samples.
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.
Guillaume-Gentil
O
O
Nestlé Research Centre, Quality and Safety Department, CH-1000 Lausanne 26, Switzerland. olivier.guillaume-gentil@rdls.nestle.com
Sonnard
V
V
Kandhai
M C
MC
Marugg
J D
JD
Joosten
H
H
D015169:Colony Count, Microbial / Q000379:methods; D044083:Cronobacter sakazakii / Q000145:classification / Q000302:isolation & purification*; D003470:Culture Media / Q000737:chemistry*; D004783:Environmental Microbiology; D004784:Environmental Monitoring / Q000379:methods*; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D006801:Humans; D016920:Meningitis, Bacterial / Q000209:etiology / Q000517:prevention & control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors; D000520:alpha-Glucosidases / Q000032:analysis
D003470:Culture Media; D000520:alpha-Glucosidases