Comparison of the traditional three-tube most probable number method with the Petrifilm, SimPlate, BioSys optical, and Bactometer conductance methodsfor enumerating Escherichia coli from chicken carcasses and ground beef
Sm. Russell, Comparison of the traditional three-tube most probable number method with the Petrifilm, SimPlate, BioSys optical, and Bactometer conductance methodsfor enumerating Escherichia coli from chicken carcasses and ground beef, J FOOD PROT, 63(9), 2000, pp. 1179-1183
A study was conducted to compare commonly used methods, such as Petrifilm a
nd SimPlate, and the rapid microbiological methods BioSys optical and Bacto
meter conductance to the standard most probable number (MPN) procedure for
enumerating Escherichia coli from poultry carcasses and ground beef. Broile
r carcasses and ground beef were evaluated in each of three replicate trial
s. Five groups of carcasses or ground beef were sampled and analyzed using
Petrifilm, SimPlate, BioSys optical, and Bactometer conductance measurement
s after temperature abuse at 37 degrees C for 0 (Petrifilm and SimPlate onl
y), 2, 4, 6, or 8 h. The correlation coefficients for the regression lines
comparing the standard E. coli MPN procedure to Petrifilm and SimPlate for
chicken and ground beef, respectively, were as follows: 0.95, 0.94, 0.93, a
nd 0.91. The correlation coefficients for the regression lines comparing th
e standard E. coli MPN procedure to BioSys optical and Bactometer conductan
ce measurements for chicken and ground beef, respectively, were -0.91, -0.9
0, -0.93, and -0.96. Although Petrifilm and SimPlate performed well, E. col
i could not be enumerated from 16.7 and 10% of samples, respectively, using
these methods. The BioSys optical and Bactometer conductance methods perfo
rmed very well when compared with Petrifilm and SimPlate. Using rapid metho
ds (BioSys optical and Bactometer conductance), results were obtained in 1
to 11 h rather than the 48 h required to conduct Petrifilm or SimPlate or t
he 5 days required to conduct the MPN procedure. These methods may allow pr
ocessors to test products and obtain results before shipping, avoiding the
cost and loss of reputation associated with a recall or foodborne illness o
utbreak.