Dominantly inherited familial amyloidosis, Finnish type (FAF) is caused by the accumulation of a 71-amino acid amyloidogenic fragment of mutant gelsolin (GSN). FAF is common in Finland but is very rare elsewhere. In Finland and in two American families, the mutation is a G654A transition leading to an Asp to Asn substitution at residue 187. We found the same mutation in a Dutch family but a Danish FAF family had a G654T mutation, predicting Asp to Tyr at residue 187. We also found the G654T transversion in a Czech family. Using GSN polymorphisms, different haplotypes were found in the Danish and Czech families. We conclude that substitution of the uncharged Asn or Tyr for the acidic Asp at residue 187 creates a conformation that may be preferentially amyloidogenic for GSN.

Dairy products have been associated with approximately half of the reported listeriosis outbreaks in Europe. The listeriosis outbreaks have mostly been linked to consumption of raw milk or products made of unpasteurized milk. Outbreaks, such as in Switzerland in 1983 to 1987 caused by unpasteurized soft cheese, in Austria in 1986 by unpasteurized milk, and in France in 1995 by a Brie-type cheese made of unpasteurized milk demonstrate the risks involved in the consumption of raw milk or soft cheeses made of unpasteurized milk. The pasteurization of raw milk, which destroys Listeria monocytogenes, does not eliminate later risk of L. monocytogenes contamination in dairy products. The outbreak in Finland from 1998 to 1999, with butter as the source, shows that dairy products made of pasteurized milk may become contaminated in subsequent stages of production with L. monocytogenes. Extensive work has been ongoing in several European countries during the last decade to prevent outbreaks and decrease the incidence of listeriosis. This work has included preventive measures in food processing plants, consumer education, and early detection of outbreaks. A marked reduction has occurred in the incidence of listeriosis in some of these countries during the 1990s, suggesting a relationship between preventive measures and reduction in listeriosis.

The amyloid protein in Finnish hereditary amyloidosis is a fragment of the actin-filament binding region of a variant gelsolin molecule. Here we demonstrate, using polymerase chain reaction and allele-specific oligonucleotide hybridization analyses of genomic DNA, a single base mutation @Y4+Ads4) in the gelsolin gene segment encoding the amyloid protein. The mutation is responsible for the expression of the variant (Asn1a7) gelsolin molecule in Finnish hereditary amyloidosis. The nucleotide substitution was found in all five unrelated patients with Finnish amyloidosis studied, but not in 45 unrelated control subjects. The mutation co-segregated with the disease phenotype in a family with Finnish amyloidosis. The results show that a single substitution in the gelsolin gene causes Finnish hereditary amyloidosis. The allele-specific oligonucleotide hybridization method provides a simple and accurate means of detecting this mutation.

Contamination routes of Listeria monocytogenes were examined in a chilled food processing plant that produced readyto-eat and ready-to-reheat meals during an 8-year period by amplified fragment length polymorphism (AFLP) analysis. A total of 319 L. monocytogenes isolates were recovered from raw materials (n ϭ 18), the environment (n ϭ 77), equipment (n ϭ 193), and products (n ϭ 31), and 18 different AFLP types were identified, five of which were repeatedly found to be persistent types. The three compartments (I to III) of the plant showed markedly different contamination statuses. Compartment I, which produced cooked meals, was heavily contaminated with three persistent AFLP types. AFLP type A1 dominated, and it comprised 93% of the isolates of the compartment. Compartment II, which produced uncooked chilled food, was contaminated with four persistent and five nonpersistent AFLP types. The equipment of compartment III, which produced cooked ready-toreheat meals, was free of contamination. In compartments that produced cooked meals, the cleaning routines, product types, and lack of compartmentalization seemed to predispose production lines to persistent contamination. The most contaminated lines harbored L. monocytogenes in coolers, conveyors, and packing machines. Good compartmentalization limited the flow of L. monocytogenes into the postheat-treatment area and prevented the undesired movement of equipment and personnel, thus protecting the production lines from contamination. In compartment II, grated cheese was shown to cause product contamination. Therefore, special attention should be paid to continuous quality control of raw ingredients when uncooked ready-toeat foods are produced. In compartment II, reconstruction of the production line resulted in reduced prevalence rates of L. monocytogenes and elimination of two persistent AFLP types.During the past decade, consumer demand for foods requiring minimal preparation time has increased the readyto-eat and ready-to-reheat chilled food markets. For the chilled food processing industry, contamination of products with Listeria monocytogenes is a major safety concern because the bacterium is widely spread in the environment, can grow at refrigerated temperatures, and may cause persistent plant contamination (10,12,19,29). In addition, some chilled food products are consumed without further heating or without adequate reheating to destroy L. monocytogenes, and therefore, these products can serve as sources of human listeriosis in outbreaks and sporadic cases.A number of studies have shown that L. monocytogenes contamination of food products primarily results from postprocessing contamination from the equipment and the processing environment (3,5,19,24,26), although the initial contamination may be introduced to the production plant via raw materials (17). The contamination routes of L. monocytogenes in the processing environment have been examined in several studies targeting meat, poultry, and fish processing plants (3,7,29,31). However, despite the incr...

Aims:  Acid and heat tolerance of 17 persistent and 23 nonpersistent Listeria monocytogenes strains, recovered from three meat‐processing plants, were investigated. Methods and Results:  The isolates were genotyped by pulsed‐field gel electrophoresis and categorized into persistent strains according to the frequency of the strain and duration of the contamination. The persistent and nonpersistent strains were challenged to acidic conditions (pH 2·4 for 2 h, 1 mol l−1 HCl were used to acidify the suspension) and to heat (55°C for 40 min) to receive a reduction in cell count. Listeria monocytogenes strains showed large variation in acid tolerance (over 6 log units) and in heat tolerance (3 log units). The persistent strains showed higher tolerance to acidic conditions than the nonpersistent strains (Student’s t‐test, P = 0·02), but significant differences in heat tolerance between persistent and nonpersistent strains were not observed. Conclusions:  The results indicate that acid tolerance may have an effect on the persistence of L. monocytogenes contamination. Significance and Impact of the Study:  This study highlights the fact that there are great differences in acid and heat tolerances between L. monocytogenes strains, and the preventive measures should be designed to be effective against the most tolerant strains.

Choroideremia (CHM) is an X-linked progressive degeneration of the choroid and retina. 12% of unrelated male patients carry deletions of the partially cloned CHM gene. In Finland, there are more than 120 living CHM patients belonging to eight apparently unrelated pedigrees. Molecular deletions involving the CHM gene have been detected in three families. We have screened the remaining five families for point mutations. In one large family a single nucleotide (T) insertion into the donor splice site of exon C leads to two aberrantly spliced mRNAs both producing a premature stop codon. The mutation can be assayed easily by amplification and digestion with Msel. Our findings provide additional evidence for the pathogenetic role of CHM mutations and provide a diagnostic tool for one fifth of the world's known CHM patients.

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