Modified most-probable-number technique for the specific determination of Escherichia coli from environmental samples using a fluorogenic method

Maria Valeria Torregrossa, Roberto Cornax, Ma Carmen Balebona, Miguel A. Moriñigo, Juan J. Borrego, Michel J. Gauthier

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7 Citations (Scopus)

Abstract

A specific and senstive modification of the most-probable-number (MPN) technique by addition of 4-methylumbelliferyl-β-D-glucuronide (MUG) to both presumptive and confirmatory media was performed. The use of this modification allows the precise determination of Escherichia coli from marine samples (seawater, sediment and shellfish) within 7 days compared to 10–12 days required by using of the standard methodology. No false-positive isolates for fluorescence reaction have been observed, although one E. coli strain fluorescent-positive on agar was isolated from nonfluorescent tubes. Klebsiella pneumoniae was the species most frequently detected from tubes with gas and fluorescence production and typical morphology on mFC agar, but failed on nutrient-MUG agar.Using a unifactorial variance analysis of the mean, fluorescence in tube and on agar has been determined as the factor which allows the detection of E. coli presence in the three sample types with high accuracy. The incorporation of MUG to the selective broth in the confirmatory test has been shown to avoid false-positive results due to shellfish tissue β-glucuronidase activity.
Original languageEnglish
Pages (from-to)235-245
Number of pages11
JournalJournal of Microbiological Methods
Volume12
Publication statusPublished - 1990

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology
  • Microbiology (medical)

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