Microbiological characterization of imported and domestic boneless beef trim used for ground beef

Abstract

The United States imports lean boneless beef trim from Australia (AUS), New Zealand (NZL), and Uruguay (URY) to meet demand for ground beef production. The reported incidence of and etiological agents responsible for foodborne diseases differ between these countries and the United States. Our objective was to determine whether current U.S. microbiological profiling adequately addresses the potential differences between foreign and domestic beef trim. We compared the hygienic status of imported and domestic (USA) beef trim by enumeration of aerobic bacteria, Enterobacteriaceae, coliforms, Escherichia coli, and Staphylococcus aureus. We also compared the prevalence of pathogens between imported and domestic samples by screening for the presence of Salmonella, Campylobacter spp., Listeria spp., and non-O157 Shiga toxin-producing E. coli (STEC). A total of 1,186 samples (487 USA, 220 AUS, 223 NZL, and 256 URY) of boneless beef trim were analyzed. Results of enumeration revealed significant differences between samples from all countries, with the lowest pathogen numbers in samples from AUS and the highest in samples from URY. Six Salmonella isolates (1 NZL, 1 URY, and 4 USA), 79 L. monocytogenes isolates (4 AUS, 5 NZL, 53 URY, and 17 USA), and 7 Campylobacter isolates (1 NZL, 1 URY, 5 USA) were found among the trim samples tested. Non-O157 STEC prevalence was 10% in NZL samples and about 30% in all of the other samples; 99 STEC strains were isolated. Serotyping of these isolates revealed that serotypes associated with hemolytic uremic syndrome were not different in prevalence between imported and domestic beef trim. Although it may be tempting to do so, these data cannot be used to compare the microbiological quality of beef trim between the countries examined. However, these results indicate that the current pathogen monitoring procedures in the United States are adequate for evaluation of imported beef trim.