Effect of high temperature on infectivity of Toxoplasma gondii tissue cysts in pork.

To study the effect of high temperature on infectivity of Toxoplasma gondii tissue cysts, pork from infected pigs was mixed with infected mouse brains and homogenized thoroughly. Twenty-gram samples of infected homogenized meat were sealed in plastic pouches, pressed to a uniform thickness of 2 mm, and subjected to water-bath temperatures of 49, 52, 55, 58, 61, 64, and 67 C for 0.01, 3, 6, 9, 12, 24, 48, and 96 min. Treated samples were digested in HCl-pepsin solution and bioassayed in mice. Toxoplasma gondii tissue cysts remained viable at 52 C for 9.5 min but not for 9.5 min at 58 C; tissue cysts were generally rendered nonviable by heating to 61 C or higher temperature for 3.6 min. Tissue cysts survived once at 64 C for 3 min. These data demonstrate that T. gondii tissue cysts are less heat resistant than encysted Trichinella spiralis larvae.

The importance of Campylobacter jejuni to the meat industry: a review.

Campylobacter jejuni is a microorganism that only recently has been implicated in gastroenteritis in humans. As appropriate methods used for detection of the bacterium have been developed, the rates of illness caused by the pathogen were found to approach or surpass those attributed to Salmonella. Substantial evidence has been gathered to document that the route for human infection is through the ingestion of adulterated food and drink. Some slaughter animals harbor this potential pathogen among the intestinal flora and, consequently, transfer of the organism to carcasses and to the resulting meat products does occur. The most frequently implicated meat is poultry, with an incidence of recovery of C. jejuni from the store-bought poultry meat reported to be at least 50%. Red meat from slaughter animals have also yielded this bacterium from carcasses, but at lower incidence levels. Foodborne disease has been associated most frequently with the ingestion of raw milk, but poultry, hamburger, and other foods have all been implicated as potential sources. However, cause and effect relating the presence of C. jejuni in meat and human gastroenteritis has not been demonstrated. Additional research is needed to determine whether C. jejuni isolated from meat causes gastroenteritis and whether all strains of the organism are virulent. Recognition of C. jejuni as a potential meatborne pathogen by the meat industry is necessary, and appropriate sanitary practices to prevent passage of the organism through meat products should be implemented.

Mineral composition of muscles of 1- to 6-year-old steers.

The diaphragm, longissimus, psoas major, semitendinosus and transversus abdominus muscles from eight or nine Angus steers were evaluated at each age of slaughter including 12, 18, 24, 30, 36, 48, 60 and 72 mo. The content of K, Fe, and Zn varied (P less than .01) with age of the steers. Ca, Na and Mg were not affected. The K content on a fat-free basis decreased from a high of 392 mg/100 g wet tissue at 24 mo of age to a low of 332 mg/100 g at 72 mo. Fe content increased with age from 2.00 mg/100 g of tissue at 12 mo to 3.73 mg/100 g at 72 mo. Concentrations of all minerals varied (P less than .01) among the five muscles evaluated. Feeding regimen had a significant effect on K, Fe and Zn, Steers fed entirely ad libitum had a higher K (17 mg/100 g more) and Fe (.19 mg/100 g more) content in their muscles than did the steers that were fed to gain .45 kg/d or those fed ad libitum for the last 6 mo before slaughter. Where significant, the magnitude of the difference in mineral content among age groups, muscles and feeding regimens was large enough to require that maturity, muscle and feeding regimen be specified when values for mineral content were reported.

Distribution of Trichinella spiralis larvae in selected muscles and organs of experimentally infected swine.

Thirty-two Hampshire-Yorkshire pigs (6 to 8 wk old) were inoculated with the Beltsville strain of Trichinella spiralis at a level of about 880 larvae/kg of body weight (about 15 kg). At about 100 kg, the pigs were slaughtered and 10-g samples of muscle and other tissues were digested in pepsin-HC1 and examined microscopically for T. spiralis larvae. The mean number of larvae recovered/gram was: tongue, 452; diaphragm, 391; obliquus abdominis internus, 130; serratus ventralis, 116; psoas major, 105; triceps brachii, 100; biceps femoris, 83; semitendinosus, 74; intercostal, 60; semimembranosus, 58 and longissimus dorsi, 37. The liver and spleen samples contained none. Larvae were found in one sample each of the blood, brain and kidney, in two samples of the heart, and in four samples of lymph tissue. Each of these samples was from a different pig except the positive samples of brain and heart, which were from the same pig. The larvae found in the blood, brain, kidney, heart and lymph were first stage larvae and, therefore, do not indicate migration of newborn larvae from the gut. The presence of these larvae in non-striated muscle tissue may have been due to contamination of the organs from infected skeletal muscle. These data confirmed previous reports of the distribution of the T. spiralis larvae among individual muscles of the carcass. Further, the data suggest that cross-contamination of organ tissue is possible during evisceration and, therefore, organ meat from infected swine cannot be assured to be free of T. spiralis larvae.

Reduction of Salmonella and fecal contamination of pork during swine slaughter.

Experiments were designed to reduce Salmonella and fecal contamination of pork, using several sanitizing methods and agents. Sanitizing the hauling vehicle and holding pens with chlorine or quaternary ammonium compounds proved ineffective in reducing carcass contamination. When the eviscerator wore a plastic glove and sanitized his knife in 82-C water before using it on each carcass, contamination was reduced about 50%. Sanitizing the eviscerator's knife in 500-ppm chlorine solution adjusted to a pH of 6.0, or in 25-ppm iodine solution reduced contamination approximately 75%.

Microbiology of Hot-Boned and Electrostimulated Meat.

Boning of unchilled beef carcasses offers potential savings in energy, labor, safety, yield, and when coupled with electrical stimulation, provides tender beef with good water-holding capacity. Breaking of unrefrigerated beef carcasses into primals, subprimals and manufactured meat products, such as ground beef, provides the potential for increased levels of spoilage and pathogenic bacteria to contaminate the meat surfaces. Research carried out to characterize the influence of hot-boning and electrical stimulation on the microbial levels on beef carcasses, primals, ground beef and meat from other species showed that hot-boning of carcasses of any species need not cause inordinate increases of any groups of microorganisms on or in the resultant meat. The electrical stimulation treatment cannot be clearly shown to be responsible for improved microbial counts but the treatment did not cause an increase in counts. Present microbiological data do not preclude use of electrical stimulation coupled to hot-boning.

Role of Government in Research on Meat Microbiology.

This paper doer not present new scientific data but rather is an attempt to explain the role of the government microbiologist in meat research. His involvement usually centers on filling actual and potential voids in the data collection process. He serves in a trilateral cooperative effort with academia and industry to provide data on developing technology, meat safety, method development and improved microbiological quality of meat. Examples of research in each of these areas are presented. Some of the examples are used to describe research which was of questionable value because though published, the research data have not yet had any measurable impact on the industry, the consumer, other scientists or the action agencies. Some ideas, presented for improving the effectiveness of the government meat microbiologist, include (a) developing and publicizing lists of research needs, (b) timely sharing of research findings, (c) minimizing repeated duplication of research, (d) prior clearing of protocols with end users of the research findings, and (e) adequate planning before the research is initiated. Possibly the most important concept presented is that the end product is not publication of the data in a peer scientific journal, but rather that the research is of adequate value so once published it is used by the meat industry, the action agencies or other scientists.

Differentiation of Salmonella Serotypes by pyrolysis-gas-liquid chromatography of cell fragments.

Pyrolysis-gas-liquid chromatography (PGLC) of whole cells and cell fragments was used to differentiate 10 Salmonella serotypes. Lyophilized samples (200 microgram) of whole cells, cell walls, flagella, and deoxyribonucleic acid from each serotype were analyzed in duplicate by PGLC. Pyrochromatograms recorded as pyrolytic elution patterns represented thermal fragmentation products of the samples. Mathematical expressions of percent similarity and percent conformity were calculated for all possible pair combinations of the 10 serotypes. Stepwise discriminant analysis of the PGLC data showed that 100 percent correct classification of the 10 serotypes was possible from the flagella or deoxyribonucleic acid pyrochromatograms. The classification matrix of the whole-cell data showed a 90 percent correct classification. PGLC of cell fragments may provide useful information for taxonomic studies of Salmonella and other microorganisms.

Survival of Campylobacter jejuni inoculated into ground beef.

Ground beef was inoculated with mixed cultures of Campylobacter jejuni, and the samples were subjected to various cooking and cold-storage temperatures. When samples were heated in an oven at either 190 or 218 degrees C, approximately 10(7) cells of C. jejuni per g were inactivated (less than 30 cells per g) in less than 10 min after the ground beef reached an internal temperature of 70 degrees C. When the samples were held at -15 degrees C over 14 days of storage, the numbers of C. jejuni declined by 3 log10. When inoculated samples were stored with an equal amount of Cary-Blair diluent at 4 degrees C, no changes in viability were observed over 14 days of storage. Twenty-five times as much C. jejuni was recovered from inoculated ground beef when either 10% glycerol or 10% dimethyl sulfoxide was added to an equal amount of ground beef before freezing as was recovered from peptone-diluted ground beef. Twice as much inoculated C. jejuni was recovered from ground beef plus Cary-Blair diluent as was recovered from ground beef plus peptone diluent.

Bacteriological Quality of Ground Beef Prepared from Hot and Chilled Beef Carcasses.

The bacteriological quality of ground beef chub packs prepared from beef sides at 2 h postmortem (hot-boned) and opposite sides conventionally chilled for 24 h at 3 C (cold-boned) were compared at the time of preparation and at 3-day intervals up to 45 days of storage at 0 C. Aerobic plate counts (APCs) in ground beef from hot-boned beef were either significantly lower or not significantly different from APCs in ground beef from cold-boned carcasses. There were no significant differences of any practical importance in Most Probable Numbers (MPNs) of coliforms and Escherichia coli between hot-boned and cold-boned ground beef stored at 0 C. Ground beef prepared from hot-boned beef offers great potential to the meat industry for energy conservation. The bacteriological quality of ground beef from hot-boned carcasses does not limit and might enhance the feasibility of boning carcasses before chilling.

Presence of Yersinia enterocolitica Serotype O:5,27 in Slaughter Pigs.

The tonsils, tongue, mesenteric lymph nodes, cecal contents, and feces from 50 slaughter pigs were evaluated for the presence of pathogenic Yersinia enterocolitica . The cecal contents and feces of two pigs were positive (4%) with the pathogenic serotype O:5,27, biotype 3, whereas all other pigs were negative for pathogenic serotypes of Y. enterocolitica . The pathogenic serotypes were isolated from the cecal contents and feces using the stomacher sampling method. The cold enrichment in phosphate buffered saline and plating in Cefsulodin-irgasan-novobiocin medium. No pathogenic serotypes were recovered using the swab sampling technique, enrichment in Irgasan-ticarcillin-chlorate, and plating in modified Salmonella-Shigella deoxycholate-calcium chloride medium. The isolation of only 4% positive pathogenic Y. enterocolitica in our sampling of pigs in one production unit provides some encouragement that detection and control procedures might be effectively implemented to reduce or eliminate serotype O:5,27 from that herd.