A chromogenic plating medium for isolatingEscherichia coliO157:H7 from beef

Autor: L. Restaino, D. R. K. Allison, E. W. Frampton, K. M. Turner
Rok vydání: 1999
Předmět:
Zdroj: Letters in Applied Microbiology. 29:26-30
ISSN: 1472-765X
0266-8254
DOI: 10.1046/j.1365-2672.1999.00569.x
Popis: There was no significant difference (P > 0.05) in the percentages of Escherichia coli O157:H7 cells recovered on BCM® O157:H7 (+) agar (69.7%) and MacConkey sorbitol agar containing 5-bromo-4-chloro-3-indoxyl-β-D-glucuronic acid (MSA-BCIG) (76.8%) vs Tryptic soy agar. Three E. coli O157:H7 strains (ATCC 35150, 43890 and 43894) were separately inoculated into raw ground beef at low (mean 0.32 cfu g -1 ) and high (mean 3.12 cfu g -1 ) levels. Using the United States Department of Agriculture (USDA) m-EC + novobiocin enrichment broth, BCM® O157:H7 (+) medium surpassed MSA-BCIG agar with overall percentage sensitivities for BCM® O157:H7 (+) of 92.1 and 94.4 compared with 52.6 and 84.7 for MSA-BCIG at low and high levels, respectively. A comparison of BCM® O157:H7 (+) and MSA-BCIG agars using naturally contaminated beef samples was made utilizing presumptively positive enrichment broths previously identified by rapid methods. The E. coli O157:H7 cells in these broths were concentrated with Dynabeads® anti-E. coli O157 before inoculating the agars. The respective percentage sensitivity and specificity values were 90.0 and 78.5 for BCM® O157:H7 (+) and 70.0 and 46.4 for MSA-BCIG. Thus, under identical pre-plating conditions, BCM® O157:H7 (+) medium displayed a greater sensitivity than MSA-BCIG for detecting E coli O157:H7 in artificially inoculated beef, and both greater sensitivity and specificity upon examining naturally contaminated beef samples.
Databáze: OpenAIRE
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