Evaluation of a chromogenic medium supplemented with glucose for detecting Enterobacter sakazakii.
A commercial chromogenic agar medium (DFI) was supplemented with glucose (mDFI) to enhance the specificity of Enterobacter sakazakii (E. sakazakii) detection. Escherichia vulneris (E. vulneris), a putative false-positive strain on the DFI medium, produces alpha-glucosidase. The enzyme alpha- glucosidase hydrolyzes a substrate, 5-bromo-4-chloro-3- indolyl-alpha,D-glucopyranoside (XalphaGlc), producing green colonies. E. sakazakii strains produced green colonies on both DFI and mDFI agar, whereas E. vulneris produced green colonies on DFI agar but small white colonies on mDFI agar. E. sakazakii and E. vulneris were also readily differentiated by colony color when the mixed culture of the two strains was plated on mDFI agar and incubated for 24 h at 37 degrees C. The results indicate that the selectivity of the commercial chromogenic agar medium could be improved by a simple supplementation with glucose.
Song
Kwang-Young
KY
JIFSAN, University of Maryland, 0220 Symons Hall, College Park, Maryland, 20742, U.S.A.
Hyeon
Ji-Yeon
JY
Shin
Ho-Chul
HC
Park
Chan-Kyu
CK
Choi
In-Soo
IS
Seo
Kun-Ho
KH
D001431:Bacteriological Techniques / Q000379:methods*; D002863:Chromogenic Compounds / Q000378:metabolism*; D044083:Cronobacter sakazakii / Q000166:cytology* / Q000302:isolation & purification* / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry*; D004925:Escherichia / Q000166:cytology / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000378:metabolism
D002863:Chromogenic Compounds; D003470:Culture Media; D000520:alpha-Glucosidases; D005947:Glucose