Trial of Heat Inactivation of Selected Viruses Following Irradiation.

Four selected viruses were irradiated in ground pork with an electron beam at absorbed doses of 4.4 to 5.27 kG. Irradiated and nonirradiated viruses were heated at four temperatures for four time intervals and assayed for surviving virus. Data were examined for evidence of irradiation-heat interaction to determine whether absorbed irradiation would sensitize virus so that a lesser amount of heat would be required for inactivation. It was determined that irradiation does not increase lability to heat to a level that has practical application in virus inactivation.

Prevalence and antimicrobial resistance of enterococcus species isolated from retail meats.

From March 2001 to June 2002, a total of 981 samples of retail raw meats (chicken, turkey, pork, and beef) were randomly obtained from 263 grocery stores in Iowa and cultured for the presence of Enterococcus spp. A total of 1,357 enterococcal isolates were recovered from the samples, with contamination rates ranging from 97% of pork samples to 100% of ground beef samples. Enterococcus faecium was the predominant species recovered (61%), followed by E. faecalis (29%), and E. hirae (5.7%). E. faecium was the predominant species recovered from ground turkey (60%), ground beef (65%), and chicken breast (79%), while E. faecalis was the predominant species recovered from pork chops (54%). The incidence of resistance to many production and therapeutic antimicrobials differed among enterococci recovered from retail meat samples. Resistance to quinupristin-dalfopristin, a human analogue of the production drug virginiamycin, was observed in 54, 27, 9, and 18% of E. faecium isolates from turkey, chicken, pork, and beef samples, respectively. No resistance to linezolid or vancomycin was observed, but high-level gentamicin resistance was observed in 4% of enterococci, the majority of which were recovered from poultry retail meats. Results indicate that Enterococcus spp. commonly contaminate retail meats and that dissimilarities in antimicrobial resistance patterns among enterococci recovered from different meat types may reflect the use of approved antimicrobial agents in each food animal production class.