ABSTRACT
AIMS: To reduce the analysis time needed for the enumeration of Escherichia coli, a rapid fluorogenic method (MUG) which takes only 48 h was compared with the standard most probable number (MPN) method which takes 6 days as described in the International Standards Organization (ISO). This study provides reliability data for the fluorogenic method applied to certain foods. METHODS AND RESULTS: Both methods were applied to 500 food samples which were analysed for E. coli enumeration. Agreement between the two methods was found in 409 (81 x 8%) samples; 81 (16 x 2%) samples gave higher values by the fluorogenic method, and only 10 (2 x 0%) samples were more effectively assayed by the ISO method. According to statistical analysis, the reliability between the methods was r = 0 x 9706, r(2) = 0 x 9421 and Cronbach's alpha = 0 x 9851. While all three values showed a high degree of correlation (P < 0 x 0001) between the two methods, McNemar's test demonstrated a significant difference between them, indicating that the MUG method was more reliable than the ISO method. CONCLUSIONS: The data suggest that the fluorogenic method is more reliable and shorter to perform than the standard ISO method. SIGNIFICANCE AND IMPACT OF THE STUDY: Comparison of the two methods may provide a rapid and more reliable alternative for the enumeration of E. coli in food samples.
Subject(s)
Escherichia coli/isolation & purification , Fluorometry/methods , Food Microbiology , Bacteriological Techniques/methods , Bacteriological Techniques/standards , Culture Media , Fluorescent Dyes/chemistry , Meat Products/microbiology , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
An assay to screen Escherichia coli in foods using MUG supplemented lauryl sulfate tryptose (LST) broth instead of tryptone water (TW) medium was evaluated. The results presented in this paper suggest that this method is more sensitive for lower levels of E. coli, faster (16-18 h vs. 6-10 days) and less expensive (2.454 vs. 2.887 EURO/sample) than the standard ISO procedure. Thus, this method may be beneficial for use when both fecal coliforms and E. coli analyses are required in food systems.