Microbiologique Microfilm™ EBEc - a Rapid Method for the Simultaneous Enumeration of Enterobacteriaceae and Escherichia coli

BACKGROUND

The Enterobacteriaceae and generic Escherichia coli are routinely enumerated in foods as part of product release criteria, or in the case of swabs, for environmental monitoring.

OBJECTIVE

Microbiologique Microfilm™ EBEc is intended to provide a rapid and easy-to-use method for simultaneous enumeration of Enterobacteriaceae and E. coli on foods and environmental surfaces. Methods: This study evaluated the performance of Microfilm™ EBEc against ISO methods (ISO 21528-2:2017 for Enterobacteriaceae and ISO 16649-2: 2001 for E. coli) in 20 food matrixes and two environmental surfaces. Inclusivity, exclusivity, lot-to-lot reproducibility, ruggedness and stability studies were also performed on Microfilm™ EBEc.

RESULTS

No significant differences and high correlation coefficients (R2) were observed between the Microfilm™ EBEc and the corresponding ISO methods in spiked food matrixes and environmental samples. Inclusivity studies showed expected results for all the E. coli and Enterobacteriaceae strains tested. In terms of exclusivity testing, all the strains tested failed to grow on Microfilm™ EBEc. A lot-to-lot study showed no significant differences in mean difference (log10) counts among the three lots of the Microfilm™ EBEc. Ruggedness studies showed no significant differences in mean difference (log10) counts at varying incubation temperatures and times. Stability studies on the Microfilm™ EBEc showed that it is stable at 2-25°C for 12 months, and at 45°C for 6 weeks.

CONCLUSIONS

The results of this study indicate that the Microfilm™ EBEc is equivalent to the corresponding ISO methods for enumeration of Enterobacteriaceae and E. coli. Highlights: Microfilm™ EBEc offers a convenient and relatively fast test method for simultaneous enumeration of Enterobacteriaceae and E. coli in 24 h and has an advantage over the corresponding ISO methods that require two assays on the same sample for enumeration of Enterobacteriaceae and E. coli Gram-negative indicator groups.

Bacteriologic and nutritional evaluation of a commercial raw meat diet as part of a raw meat safety program

This study evaluated selected bacteriologic and nutritional components of a commercially prepared ground raw horsemeat diet as part of a raw meat safety program. Six lots of meat were analyzed in triplicate. Frozen meat samples were thawed for 44 hr at 5°C. Meat samples were tested at three times during thawing (t = 0, 24, 44 hr) for selected bacteria. Samples were screened for Salmonella sp. using an enzyme-linked immunosorbent assay. Escherichia coli and total coliform bacteria were quantified using a ready-made culture medium system. Proximate, energy, macro and trace mineral composition was determined at a reference laboratory. Salmonella sp. antigen was detected in one sample of meat at t = 0 hr. Frozen meat samples had low average maximum expected numbers of E. coli and coliforms. The average maximum number of E. coli did not change significantly at t = 24 or 44 hr, but the average maximum number of coliforms increased significantly by t = 44 hr. These bacteriologic tests were easily incorporated into a raw meat safety program. Median concentrations of moisture, dry matter, crude protein, crude fat, ash, calcium, and phosphorus conformed to the guaranteed analysis but median crude fiber exceeded the guaranteed maximum. Median magnesium, potassium, and sodium concentrations conformed to the approximate nutrient content. Median concentrations of copper exceeded, whereas iron, zinc, and manganese fell below, the approximate nutrient content. Median copper and manganese concentrations exceeded the National Research Council's recommendation for adult domestic cats, whereas iron and zinc were below the National Research Council's recommendations for adult cats.

Evaluation of the petrifilm aerobic count plate for enumeration of aerobic marine bacteria from seawater and Caulerpa lentillifera

The enumeration and evaluation of the activity of marine bacteria are important in the food industry. However, detection of marine bacteria in seawater or seafood has not been easy. The Petrifilm aerobic count plate (ACP) is a ready-to-use alternative to the traditional enumeration media used for bacteria associated with food. The purpose of this study was to evaluate the usefulness of a simple detection and enumeration method utilizing the Petrifilm ACP for enumeration of aerobic marine bacteria from seawater and an edible seaweed, Caulerpa lentillifera. The efficiency of enumeration of total aerobic marine bacteria on Petrifilm ACP was compared with that using the spread plate method on marine agar with 80 seawater and 64 C. lentillifera samples. With sterile seawater as the diluent, a close correlation was observed between the method utilizing Petrifilm ACP and that utilizing the conventional marine agar (r=0.98 for seawater and 0.91 for C. lentillifera). The Petrifilm ACP method was simpler and less time-consuming than the conventional method. These results indicate that Petrifilm ACP is a suitable alternative to conventional marine agar for enumeration of marine microorganisms in seawater and C. lentillifera samples.