No abstract

S U M M A R YHalobacterium strains produce a truly extracellular proteinase which degrades gelatine and casein. It has a pH optimum of about 8 and depends upon divalent cations and a high concentration of NaCl or KC1 for activity and stability. Proteolytic enzymes were also found in cell homogenates obtained by ultra sonic treatment. A caseinolytic enzyme, probably different from the extracellular one, is associated with particles which sediment upon ultracentrifugation. A soluble peptidase of lower molecular weight is also present in the extract. Both enzymes are dependent upon divalent cations and a high concentration of NaCl or KCI for activity. In contrast to other halophilic enzymes, the proteolytic enzymes of Halobacterium sdharium are more active in the presence of NaCl than KCl at equimolar concentrations. I N T R O D U C T I O NBacteria of the genus Halobacterium are widely distributed in brines of high salt concentration. They are thus conspicuous in solar evaporation ponds of salt works, where they often become the dominating type of organisms when the salt concentration rises above 25 %. The extremely halophilic bacteria are best cultivated in complex media containing peptones and yeast extract to which at least 15 % (wlv) NaCl has been added. Best growth is obtained in media containing about 25 % salt, and when bacteria are transferred to solutions with a salt concentration of less than about 10 % they lyse rapidly.The unusual properties of halophilic bacteria make them interesting objects of study for both microbiologists and biochemists, and Larsen (1967) summarized the result of a large number of investigations on them. Special methods are often necessary in studies of their metabolism and conventional procedures are unsuitable for the purification and assay of ' halophilic ' enzymes.The extreme halophiles do not generally grow well on carbohydrates but they have a well-developed enzyme apparatus for metabolizing amino acids. In order to utilize the proteins of dead organisms in salt brines the bacteria must form proteolytic enzymes. Gibbons (1957) found that 45 out of 49 tested strains were gelatinolytic, and most of these strains also degraded casein. However, a closer study of the properties of the proteolytic enzymes of such strains has apparently not been made. It is known that the bacteria have an intracellular concentration of NaCl + KCI, which is approximately the same as the NaCl concentration of the growth medium. The halophilic bacteria's enzymes are thus active at salt concentrations which inhibit or even denature many enzymes of non-halophilic organisms. This must be reflected in marked differences in the composition and properties of the protein molecules. Ingram (1947) has

Reports of foodborne disease incidents in Sweden from 1992 to 1997 are summarized. The results are based on reports from the municipal environmental and public health authorities to the National Food Administration and from medical authorities to the Swedish Institute for Infectious Diseases Control. A total of 555 incidents, of which 84% were outbreaks, were reported, involving 11,076 ill people. In 66% of the incidents, no disease agent was determined. Bacterial agents were implicated in 25% and viruses in 8% of the incidents. Calicivirus was the most reported agent both in terms of incidents and cases. Mixed dishes was the food category most often implicated in outbreaks, and smorgasbord and casserole or stews were the subcategories that caused the most cases. The place of consumption was unknown in 8% of the incidents. In about 60% of the incidents, the implicated food was consumed in commercial food establishments; in approximately 20% of incidents, it was consumed at home. The average annual incidence of reported foodborne disease in Sweden was estimated to be 21 cases per 100,000. The average annual incidence of reported foodborne salmonellosis and campylobacteriosis was estimated to be 2.0 and 0.6 cases per 100,000, respectively. The awareness and motivation to report foodborne diseases need to be improved, but additional sources of information are needed to counteract some of the limitations of reporting discussed in this work.

T h e aim of this study was to develop a polymerase chain reaction (PCR) method for the detection of pathogenic Yersinia enterocolitica and to compare it with an official culture method (NMKL-117). Primers were selected for nested PCR directed at the attachment invasion locus, ail, on the bacterial chromosome, as well as at a sequence on the pathogenic marker plasmid, termed virulence factor, virF. The final results obtained by the two methods were similar. However, while the conventional method yielded contradictory data for some steps the PCR method provided unambiguous results. Considerable advantages, i.e. higher sensitivity and specificity of the PCR method, compared with the conventional method for detecting pathogenic Y. enterocolitica, were demonstrated i n this study.

Eighty-two samples of frozen chicken from retail stores were examined for the presence of Campylobacter, Yersinia enterocolitica, and salmonellae. Aerobic plate counts and numbers of coliform bacteria at 370C were determined. Campylobacter fetus subsp. jejuni was found in 22% of the samples, Y. enterocolitica was found in 24.5%, and Salmonella typhimurium was found in one sample (1.2%). The isolated strains of Y. enterocolitica belonged to serotypes 4, 5b, 6, and 8. Aerobic plate counts and numbers of coliform bacteria at 37°C were not found to be noticeably higher in samples containing pathogens than in pathogenfree samples. This investigation showed that chicken does contain other pathogenic bacteria than salmonellae. Campylobacter and Y. enterocolitica were isolated in much higher frequencies than Salmonella.