Spanish Botulism outbreak prompts report on risks

Spanish scientists have produced a report on the growth of Clostridium botulinum and the risk of botulism following an outbreak that affected 12 people in 2023.

In June and July 2023, an increase in botulism was detected in Spain linked to consumption of prepared food packaged under vacuum or in a modified atmosphere. This association was not confirmed microbiologically as the presence of Clostridium botulinum, or botulinum toxin, was not detected in the analysis carried out on dishes prepared from batches linked to the outbreak.

A dozen cases were reported. Patients ranged in age from 23 to 77 and seven were men. Two cases each in Italy and Norway had been to Spain. Seven people were hospitalized and four were admitted to the Intensive Care Unit. Hospital stays ranged from 11 to 69 days. In July, Grupo Empresarial Palacios Alimentación recalled Spanish omelet (tortilla de patata) and suspended production. Operations resumed in August 2023.

AESAN assessment
Considering severity of the disease, as well as the fact that not following the instructions for storage and use on the labeling of certain foods or prepared products packed under vacuum or in a modified atmosphere may pose a serious risk, the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) was asked to prepare a report. It was published in the journal Food Risk Assess Europe.

Foodborne botulism is caused by the ingestion of a neurotoxin (BoNT) produced by Clostridium botulinum. Toxins are produced by Clostridium botulinum Group I (mesophilic, with toxin production temperatures between 30 and 37 degrees C (86 to 98.6 degrees F) and Group II (psychrotrophic, capable of producing toxins at temperatures as low as 3 to 4 degrees C (37.4 to 39.2 degrees F).

Group I strains are mainly associated with cases of botulism from canned foods, given the high heat resistance of their spores, requiring treatments of at least 121 degrees C (249.8 degrees F) for three minutes to make them inactive. Group II strains can grow and produce toxins at refrigeration temperatures, so they are of importance in foods that are refrigerated or have been subjected to a gentle heat treatment.  A heat treatment of 90 degrees C (194 degrees F) for 10 minutes is sufficient for these strains to achieve commercial sterilization.

Clostridium botulinum is an anaerobic bacterium, so in the absence of oxygen it can germinate and produce the botulinum toxin, for example in plant-based preserves. However, the presence of high levels of oxygen alone is not a sufficient barrier to prevent the growth or production of toxins.

Strains can grow with pH values of 4.6 or higher, so they pose a risk in low-acid foods. The minimum water activity (aw) for growth is 0.94 for proteolytic strains and 0.97 for non-proteolytic strains.

In some meat products, such as ham, the use of nitrates and nitrites is an effective strategy. However, they can react with secondary amines, resulting in the formation of N-nitrosamines, substances with potential carcinogenic activity.

Key points to consider
Scientists said adherence to good hygienic practices throughout the production process is essential. Formulation of the product should be designed to prevent pathogen growth through pH control, water activity (aw) reduction, sodium chloride concentration, or the use of antimicrobial agents.

Strict control of storage temperatures at below 4 degrees C (39. 2 degrees F), ideally below 3.3 degrees C (37.9 degrees F) is also crucial, as is ensuring that consumers follow the storage and consumption instructions provided by the manufacturer.

In the case of sterilized (canned) foods, the heat treatment applied is sufficient to inactivate Clostridium botulinum spores. For foods with milder heat treatments, which are refrigerated, vacuum-packed, ready for consumption or that require only a slight previous heating, the risk will largely depend on the monitoring of good hygienic practices throughout the production process.

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