Type E botulism associated with vacuum-packaged hot-smoked whitefish.

On January 16, 1997 two Germans got botulism after eating hot-smoked Canadian whitefish produced in Finland. The serum sample of one of the patients contained 6 MLD/ml of botulinum toxin. The type of toxin was identified as E by the toxin neutralization test and the botulinum neurotoxin type E (BoNT/E) gene was also amplified from the serum by polymerase chain reaction (PCR), but C. botulinum could not be isolated from the positive serum sample. The remains of the hot-smoked whitefish eaten by the patients contained botulinum toxin detected by the mouse bioassay and the BoNT/E gene as determined by PCR. C. botulinum was isolated from the fish sample and it was confirmed to be type E by the mouse bioassay and by PCR. Eleven other fish samples from the same lot did not contain botulinum toxin nor any BoNT gene. The incriminated food was processed on the 9th and 10th of January, 1997 from frozen whitefish imported to Finland from Canada. The pulsed-field gel electrophoretic pattern of the isolated C. botulinum strain resembled a reference strain of North American origin. It did not match any C. botulinum strains isolated from the Baltic sea-bottom or from the fish caught in the area indicating that the fish was contaminated by C. botulinum in Canada. The conditions resulting in toxin production could not be identified. The safety problems associated with vacuum-packaged hot-smoked fish seem to be of utmost concern and the product is one of the most important botulism food vehicles processed on an industrial scale. Temperature monitoring and the use of time-temperature indicators are to be recommended in order to ensure adequate storage temperature from processing through to consumption. Allowing the use of nitrate and nitrite together with sufficiently high NaC1 concentration in this particular product should also be considered.

Effect of various gas atmospheres on the growth and survival of Campylobacter jejuni on beef.

Pieces of fresh beef were inoculated with three strains of Campylobacter jejuni. The meat was then allocated to three treatments: (a) vacuum packaged, (b) packaged in an atmosphere of 20% CO2 + 80% N2, and (c) packaged into sterile Petri dishes in anaerobic cultivation boxes, which were filled with a gas mixture of 5% O2 + 10% CO2 + 85% N2. The packaging material in the first two treatments was PA 80/PE 100-PE 100/PA 80/PE 100. The survival of Campylobacter cells was followed at 37 degrees C, 20 degrees C and 4 degrees C for 48 h, 4 days and 25 days, respectively. At 37 degrees C the counts of two Campylobacter strains increased in each package treatment for 48 h. At 20 degrees C and at 4 degrees C the counts of the same two strains decreased by 1 to 2 log units and 0.5 to 1 log unit, respectively, during storage. The survival of the two strains was about the same in all package treatments. The third strain was the most sensitive of the strains studied. At 37 degrees C its numbers increased only in the optimal gas atmosphere; at 20 degrees C the strain was not detectable after 24 to 48 h storage and at 4 degrees C after 4 days storage. The aerobic plate counts were determined for all samples at the same time as Campylobacter counts. The high indigenous bacterial numbers of the meat samples did not appear to have a great effect on the survival or growth of campylobacters.

Growth and survival characteristics of Campylobacter jejuni in liquid egg.

Growth and survival of four Campylobacter jejuni strains in yolk, in liquid whole egg and in white during aerobic storage at 37, 20 and 4 degrees C was followed. In 48 h at 37 degrees C the cell counts of C. jejuni increased by about 3 log10 units in yolk and 1.60-3.35(10) log units in liquid whole egg. The growth of C. jejuni was slightly better in yolk than in liquid whole egg. At 20 degrees C during 48 h the cell counts decreased by about 0.5-1.5 log10 units in yolk and in liquid whole egg. At 4 degrees C the decrease in cell counts after 21 days ranged from 1 to 2 log10 units, except for one strain, KH3, which could not be detected after 14 days storage in yolk. In liquid whole egg the cell counts of this strain also decreased considerably during storage. In white the number of inoculated C. jejuni cells decreased rapidly. The killing effect of white was shown to be temperature-dependent; at 37 and 20 degrees C no positive samples were detected after 24 h and at 4 degrees C no positive samples were found after 48 h.

Oxytetracycline residues in meat and kidney tissue after intramuscular or intramammary treatment as determined by a chemical-physical method and compared to a microbiological method.

Two adult cows and three calves were treated intramuscularly with an oxytetracycline (OTC) preparation. The dose was about 5 mg/kg. The animals were slaughtered eight days after the treatment and their kidneys and muscle samples were taken for analysis. Twelve cows were treated intramammarily with an OTC preparation 12 hours before slaughter. Six of the cows were treated in two udder quarters with a preparation containing 200 mg OTC chloride per dose; the other six were similarly treated in four quarters with four doses. When the kidneys of all the animals were studied for the presence of inhibitory substances using the official Finnish microbiological meat inspection method, all were found negative. The OTC concentration of the different tissue samples was determined by a chemical-physical method, based on thin-layer chromatography and on the UV-fluorescence of OTC. The muscle samples of the cows given OTC i.m. were negative except near the site of injection, where the concentrations were 4 mg and less than 0.5 mg (traces) per kg. The corresponding kidney concentrations of OTC were less than 0.5 and about 0.5 mg per kg respectively. All except one kidney sample of the calves given OTC i.m. were found to be negative. Traces of OTC (less than 0.5 mg/kg) were found in all but one kidney sample of the cows treated intramammarily with OTC. Traces of OTC were found in two muscle samples of the cows treated intramammarily with 2 X 200 mg OTC and in two muscle samples of the cows similarly treated with 4 X 200 mg OTC. All the other samples were negative. The authors stress the need for a change in the present Finnish directives on the use of antibiotics in food animals.