Recovery of Escherichia coli biotype I and Enterococcus spp. during refrigerated storage of beef carcasses inoculated with a fecal slurry

• Published in: Journal of food protection 1999-08, Vol.62 (8), p.944-947
• Main Authors: Galicioglu, M, Buege, D.R, Ingram, S.C, Luchansky, J.B
• Format: Article
• Language: English
• Subjects: Abattoirs; Animals; beef; Biological and medical sciences; biological techniques; Cattle; cold storage; Colony Count, Microbial; detection; duration; Enterococcus; Enterococcus - isolation & purification; Escherichia coli; Escherichia coli - isolation & purification; evaluation; fat; feces; Feces - microbiology; food contamination; Food Handling - methods; Food Handling - standards; Food industries; food storage; Fundamental and applied biological sciences. Psychology; indicators; meat; Meat - microbiology; Meat and meat product industries; meat carcasses; microbial contamination; population density; Refrigeration; sampling; slurries; viability
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-62.8.944

Three beef front quarters/carcasses were inoculated with a slurry of cattle manure. During storage at 4 degrees C, two sponge samples from each of three sites (i.e., 100 cm(2) from each of two fat surfaces and 100 cm(2) from a lean surface) were taken from each of the three carcasses on days 0, 1, 3, 7, and 10 after inoculation. The initial numbers of Escherichia coli averaged 2.0 log(10) CFU/cm(2) (1.21 to 2.47 log(10) CFU/cm(2)) using the Petrifilm method and 2.09 log(10) most probable number (MPN)/cm(2) (0.88 to 2.96 log(10) MPN/cm(2)) using the MPN method. The initial numbers of enterococci averaged 3.34 log(10) CFU/cm(2) (3.07 to 3.79 log(10) CFU/cm(2)) using kanamycin esculin azide agar. In general, an appreciable reduction in the numbers of E. coli occurred during the first 24 h of storage; for the Petrifilm method an average reduction of 1.37 log(10) CFU/cm(2) (0.69 to 1.71 log(10) CFU/cm(2)) was observed, and for the MPN method an average reduction of 1.52 log(10) MPN/cm(2) (0.47 to 2.08 log(10) MPN/cm(2)) was observed. E. coli were not detected (< -0.12 log(10) CFU/cm(2)) using Petrifilm on day 7 of the storage period on two (initial counts of 1.21 and 2.29 log(10) CFU/cm(2)) of the three carcasses. However, viable E. coli cells were recovered from these two carcasses after a 24-h enrichment at 37 degrees C in EC broth. Viable E. coli cells were detected at levels of -0.10 log(10) CFU/cm(2) on the third carcass (initial count of 2.47 log(10) CFU/cm(2)) after 7 days at 4 degrees C. No significant difference in recovery of viable cells was observed between the MPN and Petrifilm methods on days 0, 1, and 3 (P > 0.05). However, viable E. coli cells were recovered from all three carcasses by the MPN method on day 7 at an average of -0.29 log(10) MPN/cm(2) (-0.6 to -0.1 log(10) MPN/cm(2)). On day 10, viable cells were recovered by the MPN method from two of the three carcasses at -0.63 and -0.48 log(10) MPN/cm(2) but were not recovered from the remaining carcass (< -0.8 log(10) MPN/cm(2)). Similar to E. coli, the greatest reduction (average of 1.26 log(10) CFU/cm(2), range = 1.06 to 1.45 log(10) CFU/cm(2)) in the numbers of enterococci occurred during the first 24 h of storage. Because of higher initial numbers and a slightly slower rate of decrease, the numbers of Enterococcus spp. were significantly higher (P < 0.017) than the numbers of E. coli Biotype I after 3, 7, and 10 days of storage. These results suggest that enterococci may be useful as an i