Survival of Salmonella typhimurium and Staphylococcus aureus in Genoa salami of varying salt concentration.

Genoa salami prepared using three different salt concentrations (2.0, 2.75 and 3.3%) were inoculated with 2.0 x 10(3) and 1.1 x 10(3) bacteria/g of Salmonella typhimurium and Staphylococcus aureus respectively. Over a period of 74 days samples were taken and analyzed for water activity and pH, counts of S. aureus and presence of Salmonella. After 11 days of dry-curing Salmonella could no longer be detected by preenrichment followed by selective enrichment procedures. Viable S. aureus were still found after 74 days of dry-curing. The results of this study would suggest that water activity and pH measurements are useful in evaluating the safety of dry-cured products.

Destruction of Trichinella spiralis spiralis during the preparation of the "dry cured" pork products proscuitto, proscuittini and Genoa salami.

Genoa salami, proscuittini and proscuitto were prepared from pork carcasses that were heavily infected experimentally with Trichinella spiralis spiralis. Genoa salami was prepared with salt concentrations of 2.0%, 2.75% and 3.3%. Proscuitto was prepared by two procedures approved by Agriculture Canada. At various times postpreparation, samples of the various cured products were taken and examined by pepsin digestion and rat bioassay for the presence of viable trichinae. Water activity and pH of the cured meat were also determined. Curing of the various products was shown to destroy the Trichinella larvae. Pepsin digestion revealed that larvae progressively became loosely coiled, uncoiled and more subject to digestion (ghost larvae) during the curing process. Rat bioassay revealed the presence of viable trichinae in the proscuitto prepared using a sodium chloride salt mixture at day 34 but not at day 48 postpreparation. All other bioassays carried out on Genoa salami between 13 and 42 days postpreparation, on proscuittini between days 27 and 69 and on proscuitto between days 34 and 69 were negative for viable trichinae. Under the conditions of this study, preparing Genoa salami with salt concentrations as low as 2% did not appear to affect the destruction of Trichinella larvae.

Microbiological safety of traditional and starter-mediated processes for the manufacture of Italian dry sausage.

Microbiological changes occurring during the commercial manufacture of Italian dry sausages (Genoa and salametti) were studied in two urban Canadian centres over a 5 month period. A comparison was made between 6 plants which used bacterial starter cultures and 4 plants where more traditional processes (without starters) were used. A total of 600 samples of raw, fermented and finished products were tested for the presence of coliforms, salmonellae, staphylococci, streptococci, the rate of pH reduction and final water activity (aW). Numbers of total bacteria peaked earlier and were significantly higher in sausages at the fermentation stage produced with starter cultures than in those traditionally manufactured. This corresponded with a more rapid drop in pH of the starter-inoculated products. Staphylococci and streptococci were significantly higher in starter-fermented Genoa sausages at the fermentation stage, but no significant differences were seen in the microbiological content or aW of mature finished sausages manufactured by the two different techniques. Of 128 randomly chosen isolates of coagulase-positive staphylococci, 34.4% were enterotoxin producers and 80% of these produced type A toxin. Enterotoxigenic staphylococci were found in 2 different samples of finished salametti and one sample of finished Genoa made with starter cultures and in one sample of finished Genoa made without added culture. Total numbers of staphylococci in these samples were not greater than 500/g. No correlation between the method of manufacture and presence of enterotoxigenic staphylococci could be made. Five subsamples from one lot of raw Genoa were the only samples positive for Salmonella during this study. Results indicated that low temperature traditional fermentations can yield products which are as safe as those produced by the higher temperature starter-controlled process. One of the most important elements in the traditional process was believed to be the selection and use of raw materials of the highest possible quality.

Occurrence and significance of streptococci in fermented Italian type dry sausage.

Commercial cultures used in Canada for the manufacture of Italian dry sausage were examined to determine their microbial composition and suitability for low temperature (less than or equal to 20 degrees C) meat fermentations. Temperature optima in both laboratory media and commercial meat mixtures were generally too high to allow these cultures to be of substantial advantage in this application. In addition, media used currently for the enumeration of streptococci and related organisms from fermented meat products were found to be inadequately specific and often required confirmatory inspection of colonies by conventional phase contrast microscopy. Streptococci were isolated from Italian dry sausage manufactured commercially with and without added starter cultures. Streptococci persisted in sausages produced by both techniques with slightly higher numbers present in starter-acidulated sausages. About 55.5% of the 312 streptococci studied were enterococci (Lancefield's Group D). Streptococci were found in several samples of commercial starter cultures but it was felt that elevated ripening temperatures used for sausage manufactured by the starter-mediated process and meat handling practices were more important factors influencing streptococci recovery from sausage material.

Survey of chloramphenicol residues in diseased swine.

Tissue samples from 279 hogs suspected of having received antibiotic treatment were collected at federally-inspected abattoirs and submitted for chloramphenicol residue analysis during August and September 1984. Injection sites (when present), kidneys or muscle samples were tested by one of two gas chromatographic methods. Kidney samples were also tested at the abattoirs by the Swab Test On Premises. Thirty-one animals (11%) were found with detectable levels ranging from 1 part per billion to 5727 ppb. Highest levels were found at the injection sites, while levels in muscle tissue did not exceed 500 ppb. None of the kidneys from animals found to contain chloramphenicol residues produced a positive Swab Test On Premises result attributable to the presence of chloramphenicol. Twelve kidneys from animals free of chloramphenicol residues produced positive Swab Test On Premises results. Of these, five contained penicillin or streptomycin, but antibiotic residues were not detected in the remaining seven. In addition to the samples collected for this survey, samples from eight hogs representing a herd which had been treated for pneumonia were submitted by an abattoir in Manitoba in November 1984. Chloramphenicol levels in these animals ranged from 0.1 to 73 parts per million in the injection sites, and from 0.04 to 21 ppm in the muscle tissues. The survey data indicated that there were a significant number of animals reaching the abattoirs with detectable chloramphenicol residues, and that the Swab Test On Premises procedure was ineffective in detecting these animals.

Prevalence of Salmonella and Thermophilic Campylobacter in Fresh Pork, Beef, Veal and Poultry in Canada 1.

A national surveillance program was undertaken in Canada to establish the prevalence and distribution of Salmonella and thermophilic Campylobacter biotypes in slaughter animals and poultry. During the years 1983 to 1986, samples were collected from federally inspected abbatoirs across Canada and tested at regional laboratories. The laboratory isolation procedure for thermophilic Campylobacter included selective enrichment and isolates were characterized according to Lior's biotyping scheme. Salmonella were isolated from 17.5% pork, 2.6% beef and 4.1% veal carcasses. Thermophilic Campylobacter were isolated from 16.9% pork, 22.6% beef and 43.1% veal carcasses. Salmonella were isolated from 69.1 % turkey and 60.9% chicken carcasses, and thermophilic Campylobacter were isolated from 73.7% and 38.2% turkey and chicken carcasses, respectively. Salmonella typhimurium was the most frequently isolated serotype, and predominant in broiler chickens from 1983 to 1985. Salmonella brandenburg was predominant in pork, and Salmonella schwarzengrund was the primary serotype from turkey carcasses. Campylobacter jejuni biotypes I and II were the most frequently isolated biotypes from beef, veal and poultry. Although Campylobacter coli biotype I was the predominant thermophilic Campylobacter in pork, 41.1% of the biotyped isolates from pork were C. jejuni biotypes I and II.

Thin layer chromatographic/bioautographic method for identification of antibiotic residues in animal tissues.

An analytical method for the identification of the residues from 14 commonly used antibiotics is presented. The technique is based on selective tissue extraction followed by thin layer chromatography (TLC)/bioautography. Antibiotic residues are extracted from the tissues with methanol and methanol-HCl (98 + 2). The methanol extract is further extracted with chloroform to isolate groups of antibiotics. The extracts are spotted onto TLC plates and developed in suitable solvent systems. Developed plates are placed on set medium seeded with Bacillus subtilis and a bioautograph is produced. The locations of zones of inhibition are used to identify antibiotic residues. Recoveries of antibiotics were quantitative, while the effect of naturally inhibiting components of the matrix was minimized. The sensitivity of the method can be adjusted through minor modifications, which allows its use in routine regulatory analysis.

Trace element levels in liver and kidney from cattle, swine and poultry slaughtered in Canada.

Levels of arsenic, cadmium, copper, mercury and lead were determined in approximately 650 samples of liver and kidney from cattle, swine and poultry slaughtered in Canada during 1979-81. In addition zinc levels were determined in livers and kidneys from swine, and selenium and zinc levels were determined in the livers and kidneys from cattle. Depending on the element several methods of atomic absorption spectroscopy were used to analyze samples including flame, hydride generation, cold vapour generation and graphite furnace atomization. Analyses were also done by plasma emission spectroscopy. Levels of arsenic over 2.0 micrograms/g were detected in 0.9% of swine livers and 0.3% of swine kidneys. Cadmium levels higher than 1.0 micrograms/g were detected in 0.3% of cattle livers, 10.8% of cattle kidneys, 1.8% of swine kidneys, 0.4% of poultry livers and 0.3% of poultry kidneys. Levels of copper over 150 micrograms/g were detected in 0.4% of cattle and swine livers. Levels of lead over 2.0 micrograms/g were detected in 1.4% of poultry livers and 1.6% of poultry kidneys. The highest level of mercury detected in all species was 0.25 micrograms/g and the highest level of selenium was 1.9 micrograms/g. Zinc levels of over 100 micrograms/g were detected in 1.7% of cattle livers, 0.2% of cattle kidneys and 5.0% of swine livers.

Survey of antibiotic residues in Canadian slaughter animals.

Kidneys and urine of cattle, swine, sheep and chickens were tested for bacterial growth inhibitors using Bacillus subtilis and Sarcina lutea as test organisms. Results were as follows: 211 beef kidneys four positive, 611 swine kidneys five positive, 27 sheep and 120 chicken kidneys all negative, 2108 beef urine 76 positive, 2409 swine urine 186 positive, 176 sheep urine 17 positive. Strongest reactions were obtained with B. subtilis on phosphate buffered pH 6.0 plates. Larger zones were produced by urine from injected animals than by tissue samples.

Studies on the wholesomeness of ready-to-eat meat products. II. Chemical evaluation of comminuted heated products.

Chemical parameters obtained for 280 samples randomly selected from a variety of ready-to-eat meat products were used to assess nutritional value and wholesomeness. The products investigated in this study include wieners, bologna, meat loaves, sausages, liver products and mortadella. Evaluations of gross composition (moisture, fat, protein,) were found to be insufficient to fully characterize these products. Fat/protein and water/protein quotients reflected well on the nutritional quality. Limitations in the application of these and other parameters are shown. Correlations of physico-chemical parameters such as redox-potential and available water to susceptibility to bacterial spoilage within this closely defined group were statistically insignificant.

Studies on the wholesomeness of ready-to-eat meat products. I. Bacteriological evaluation of comminuted heated products.

Bacteriological studies were conducted on comminuted heated types of ready-to-eat meat products. Seventy-five per cent of the samples showed total counts in the range of 100-10,000 organisms per gm. Of potential food poisoning organisms, coagulase positive staphylococci were present in 4% and Clostridium perfringens in 1.7% of all samples in low numbers. Of indicator organisms for fecal and sewage contamination, Escherichia coli were found in 3.2% and Streptococcus fecalis in 5.4% of the samples. The heat treatment applied during processing is not sufficient to destroy these organisms.

Studies on the bacterial floral of condemmed portions from arthritic hogs.

Studies were conducted on the bacterial floral of 122 excised joints and related iliac and inguinal lymph nodes, 118 whole hams and 42 shoulders from condemned arthritic hog carcasses. Erysipelothrix insidiosa was isolated from 15% of the joints and lymph nodes, 20% of the hams, and 33% of the shoulders. Beta-hemolytic streptococci were recovered from 12% of the joints and lymph nodes, 49% of the hams, and 54% of the shoulders. Staphylococcus aureus was found in 3% of the joints and lymph nodes, 16% of the hams and 14% of the shoulders. Gross tissue changes were not pathognomonic for any causative organism.

Studies on the contamination of products produced by rendering plants.

Studies on the bacterial contamination in rendered product and the environment of five rendering plants were carried out. From a total of 180 samples examined, total bacterial and anaerobic spore counts were conducted on 135. Plants with melter systems produced a sterile product which was recontaminated before reaching the finished stage. Two plants with continuous rendering systems did not achieve sterilization of the product during the heating process. Spore forming organisms regularly survived heating in the continuous rendering system. Salmonellae were isolated from samples collected in four of the five plants under study. Pathogenic Clostridia, especially Cl. novyi, Cl. septicum and Cl. perfringens were present in samples from all plants. Other pathogens found were Staphylococci, Streptococci, Corynebacteria and Pasteurella.

Bacteriological studies on meat pies and frozen prepared dinners.

A bacteriological survey of meat pies, frozen prepared dinners and entrees indicated that their bacterial populations were related to the components, the environment and handling in manufacture. Results were correlated with microbiological examinations of ingredients, line samples and plant environmental samples. Total bacterial counts, coliform counts and Staphylococcus counts of the finished product were low. Coliform organisms found were primarily Aerobacter spp. originating with the frozen vegetables. Enterococci were also found in the frozen vegetables and finished product. Both enterococci and Aerobacter organisms were recovered from the plant environment where they appeared to multiply. Many of the plant personnel carried coagulase-positive staphylococci in the throat or nasal cavity, and this was indicated as a possible source for these organisms found in low numbers in the finished product. Cooking of the products produced sterility except for the survival of some spore forming Bacillus spp. The presence of a poultry slaughtering operation adjacent to the manufacturing area was considered to contribute to microbial contamination of the air in the plant.