In February 1999, an outbreak of listeriosis caused by Listeria monocytogenes serotype 3a occurred in Finland. All isolates were identical. The outbreak strain was first isolated in 1997 in dairy butter. This dairy began delivery to a tertiary care hospital (TCH) in June 1998. From June 1998 to April 1999, 25 case patients were identified (20 with sepsis, 4 with meningitis, and 1 with abscess; 6 patients died). Patients with the outbreak strain were more likely to have been admitted to the TCH than were patients with other strains of L. monocytogenes (60% vs. 8%; odds ratio, 17.3; 95% confidence interval, 2.8-136.8). Case patients admitted to the TCH had been hospitalized longer before cultures tested positive than had matched controls (median, 31 vs. 10 days; P=.008). An investigation found the outbreak strain in packaged butter served at the TCH and at the source dairy. Recall of the product ended the outbreak.

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Aim:  To screen and characterize toxic, heat‐stable substances produced by food borne strains from Bacillus subtilis group. Methods and Results:  Using the boar sperm motility inhibition assay, six isolates from two outbreaks, out of the 94 isolates from 26 foods, were found to produce ethanol‐soluble heat‐stable substances that were toxic to sperm cells by depleting the mitochondrial membrane potentials. The toxic isolates were identified as Bacillus subtilis and B mojavensis. Colon carcinoma cells (Caco‐2) were used to model the contact with the human digestive tract. The extract of B. subtilis F 2564/96 depolarized the mitochondria in intact Caco‐2 cells similarly as in sperm cells. The substance responsible for these effects was purified using HPLC and identified by electron spray ionization ion trap mass spectrometry analysis as amylosin. The temperature requirement for amylosin production was 21–37°C for B. subtilis and 11–21°C for B. mojavensis. Both species produced amylosin in air as well as in 7–8% CO2 with 8–9% O2. Conclusions:  Food borne illness related strains of B. subtilis and B. mojavensis, produced the heat‐stable toxin amylosin. Significance and Impact of the Study:  This is the first report that suggests a role for the heat‐stable, ion‐channel forming toxin amylosin, as a virulence factor in food borne Bacillus.

The prevalences of various genotypes of enterotoxin gene-carrying (cpe-positive) Clostridium perfringens type A in 24 different food poisoning outbreaks were 75% (chromosomal IS1470-cpe), 21% (plasmid-borne IS1470-like-cpe), and 4% (plasmid-borne IS1151-cpe). These results show that C. perfringens type A carrying the plasmid-borne cpe is a common cause of food poisoning.