Recent outbreaks of human tuberculosis in the United States caused by Mycobacterium bovis have implicated cheese originating in Mexico as a source of these infections. A total of 203 samples of cheese originating inMexico were cultured, and M. bovis was recovered from one specimen. Therefore, M. bovis can be recovered from cheese and may be a source of human infections.Bovine tuberculosis, caused by Mycobacterium bovis, is a zoonotic disease that also affects humans. Although people are generally infected through the inhalation of droplet nuclei, a significant proportion of human cases involve extrapulmonary tuberculosis, presumably caused by the consumption of nonpasteurized milk or dairy products (23). Indeed, milk pasteurization requirements in the United States were developed to prevent many food-borne infections, including tuberculosis, botulism, and scarlet fever, caused by consuming contaminated milk or dairy products (5). With the implementation of strict pasteurization requirements and a mandatory control program for bovine tuberculosis in live animals, the incidence of M. bovis infections in cattle in the United States has decreased to an all-time low of less than 0.001% (1). Consequently, human cases of M. bovis infections in the United States have also declined (23). However, several reports have shown an elevated incidence of human tuberculosis due to M. bovis in certain regions of the United States (2,7,14). For example, a study in San Diego County, CA, found that 129 of 1,931 (6.7%) culture-positive tuberculosis cases in the County were due to M. bovis (14). A similar epidemiologic investigation in New York City also reported that 1% of culturepositive tuberculosis cases in this area were due to M. bovis (4). In both reports, patients of Hispanic ethnicity were especially at risk and approximately one-third of the cases occurred in children. In both instances, epidemiologic investigations indicated that the consumption of unpasteurized dairy products, including soft fresh cheese originating in Mexico may have accounted for these cases (4). Therefore, to investigate this possibility, a survey for the presence of M. bovis in fresh cheese products entering the United States from Mexico was initiated as a collaborative project between USDA-National Veterinary Services Laboratories (NVSL) and the California Animal Health and Food Safety Laboratories.A total of 203 cheese samples were collected from travelers entering California at the United States Customs and Border Protection Port in San Ysidro, San Diego, CA, from March through August 2005. All cheese samples had been purchased by individuals for private consumption and were being imported through noncommercial channels. Thus, whether these products were derived from pasteurized or unpasteurized milk is unknown. These samples were shipped to USDA-NVSL for mycobacterial culture. For this, 5-g portions of cheese were weighed, aseptically transferred into a sterile stomacher bag containing 45 ml of sterile 2% sodium citrate, and homogenized in a stomac...

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Carbon monoxide (CO), recently approved as a modified atmosphere packaging (MAP) gas, has the potential to extend color shelf life in case‐ready beef. The objective was to determine how CO versus traditional high oxygen MAP treatments affect beef quality. Strip loins were enhanced with a commercial phosphate–salt solution. Steaks were cut, packaged in atmospheres containing either 0.4% CO/30% CO2/69.6% N2 (HiOx) or 80% O2/20% CO2 (HiOx), aged in the dark for 12 and 26 days, and placed in a lighted retail display case. Steaks were visually evaluated by trained panelists using a 7‐point color scale and a 5‐point surface sheen scale. On days 14 and 28, packages were opened, and steaks were cooked for consumer evaluation. Cooked steaks were cut through for internal cooked color evaluation. Results indicate that CO had no effect on flavor or acceptability and minimal effects on other characteristics, such as color, sheen and purge loss. If the CO environment provides microbiological stability through 28 days, it can be expected that the raw product appearance will not differ from steaks in traditional HiOx packaging. PRACTICAL APPLICATIONS To prevent surface browning, which occurs over time due to high oxygen environments, carbon monoxide (CO) can be used in modified atmosphere packaged (MAP) fresh beef because it binds very strongly to the meat pigment myoglobin, allowing it to maintain its bright red color and extending its shelf life. Strip loin steaks were packaged in high oxygen MAP or high oxygen plus CO packaging then evaluated by a panel of 100 consumers after 14 and 28 days of storage. CO had some effect on raw color, surface sheen and interior cooked color compared to the high oxygen atmosphere when steaks were evaluated after 14 days. CO had no effect on flavor or acceptability and only minimal effects on other characteristics. Use of this recently approved MAP gas can extend the color shelf life of beef.

The objective of this study was to evaluate the effects of enhancement solutions containing sodium lactate or sodium lactate/sodium diacetate on E. coli K12 transmission to beef strip steaks and in purge. Solutions containing salt, phosphate, and shelf‐life enhancers were injected to 10% over initial weight of the steaks. Lactate or lactate/diacetate addition to a solution inoculated with 6 log10E. coli K12 CFU/mL was equally effective in limiting growth resulting in a 1‐2 log10 CFU/g reduction when compared to salt/phosphate in steaks. When inoculation level was 3 log10 CFU/mL in the enhancement solution, microbial growth was detectable only in the purge of steaks enhanced with salt/phosphate only. Lactate increased CIE L* value and b* and decreased a* values when compared to the control. Lactate‐/diacetate‐containing solutions decreased L* values when compared to lactate alone. Lactate/diacetate also reduced purge loss from steaks compared to lactate and salt/phosphate solutions.