Background 

The United States currently imports lean boneless beef trim to meet demands of ground beef production. For the purpose of microbial analysis, imported products are treated as domestic products. However, there is little information on the microbial status of imported beef and virtually none of the existing data has been collected using modern techniques. The primary countries that supply this beef trim are Australia, New Zealand, and Uruguay. The incidence and etiological agents responsible for foodborne disease differ between these countries and the United States. One example is the variation in serotypes of Shiga toxin-producing E. coli (STEC) most commonly associated with foodborne disease. In the United States and Europe E. coli O157:H7 is the most frequent cause of STEC-associated disease, whereas in Australia and New Zealand STEC infections are due to serotypes O111 and O26.   

The objective of this study was to identify differences in the hygienic status and pathogen load between imported and domestic boneless beef used for ground beef.

Methodology 

Samples (n=1,040) of imported and domestic beef trim were enumerated and characterized for the following: Total aerobic bacteria (APC), Enterobacteriaceae (EB), coliform bacteria (CF), E. coli (EC), and Staphylococcus aureus (SA). The prevalence of non-O157 STEC, Salmonella, Campylobacter, and Listeria were also determined.

Findings 

Enumerations of APC, EB, EC, CF and SA showed that of the four countries that supplied beef trim, samples from Uruguay had the highest levels of each while samples from Australia had the lowest (See Table 1). The levels of APC were different (statistically significant at P<0.05) between each country.  No significant differences were found in EB, EC, and CF levels for Australian, New Zealand, and domestic trim. SA levels were approximately the same for the domestic and Uruguayan trim. There were also differences in the prevalence of countable EB, EC, CF and SA plates (i.e. >10 CFU). The frequency of positive plates for EB, EC and CF, among Australian and New Zealand samples, was significantly lower (P<0.05) than domestic and Uruguayan trim. Frequency of SA in Uruguayan trim was significantly higher (P<0.05) than in the others.   

The levels of Campylobacter and Salmonella were very low in all samples. Seven isolates of Campylobacter were found and five Salmonella isolates were found. Of the Salmonella isolates, one from New Zealand was a Typhimurium that possessed an antibiotic resistance pattern that is commonly found in that serotype.   

The prevalence of Listeria species and LM was significantly higher (P<0.05) in Uruguayan trim. Nearly one-quarter (24%) of Uruguayan trim harbored LM compared to 2-5% for the other three countries. Trim samples from Australia and Uruguay harbored outbreak-related serotypes of of LM. Multiple species of Listeria as well as multiple serotypes of LM were found in Uruguayan samples.

Implications   

Overall, the results of this study indicate that differences exist between imported and domestic trim destined for ground beef. The data also suggest that importers of beef trim should work with their suppliers, focus especially on Uruguayan suppliers to reduce contamination and improve slaughter practices.