Scientists focus on Clostridium at FAO meeting

Experts have met to discuss the risks and knowledge gaps around Clostridium botulinum and Clostridium perfringens.

At a Food and Agriculture Organization (FAO) meeting in Rome in February, experts reviewed recent scientific developments, data, and evidence, including a review of the disease burden, attribution to food commodities of high public health concern, analytical methods in food commodities, and control measures.

Foodborne botulism, caused by botulinum neurotoxin-producing clostridia, is a severe and potentially fatal disease resulting from the ingestion of pre-formed toxin in foods that are improperly preserved or time-temperature abused and in which clostridia have grown.

Clostridium perfringens typically causes relatively mild, self-limiting, gastroenteritis. Recent data support a role for food in the epidemiology of Clostridiodes difficile infections.

It is hoped work will contribute to the development of improved food safety guidelines, helping to reduce the risks posed by different Clostridium species.

Importance of temperature
Clostridia produce spores that persist for a long time in the farm and processing environments and then contaminate foods. Spores are resistant to common control measures such as cooking, pasteurization, and antimicrobial treatments including sanitizers.

With foodborne botulism and Clostridium perfringens, the spores must germinate and vegetative bacteria multiply in the food which, when eaten, results in foodborne illness. However, botulism is caused by pre-formed neurotoxin in the food whereas Clostridium perfringens causes gastrointestinal illness when the high numbers of vegetative cells consumed in the food sporulate in the large intestine and enterotoxin is released.

Scientists reviewed the scientific literature and information submitted in response to a call for data.

They said because of the stability of clostridial spores, it is impossible to eliminate them from foods without sterilization. Strict temperature control is necessary to prevent growth.

Growth of foodborne clostridia may be controlled by additional hurdles such as salt, reduced pH or water activity, nitrite, and/or the inclusion of other food ingredients with inhibitory properties. In cases of botulism, specialist skills and equipment are required for toxin detection and the provision of antitoxin.

Available control measures
Established control measures to reduce or eliminate botulinum spores through thermal treatments are 121 degrees C (249.8 degrees F) for 3 minutes for Group 1 spores or 90 degrees C (194 degrees F) for 10 minutes for Group II spores.

The mouse bioassay remains the gold standard assay for detection and quantitation of BoNT but requires costly and specialized facilities, a high level of technical competency, and has safety and ethical concerns.

Predominant foods associated with outbreaks of Clostridium perfringens are meat and poultry products that support multiplication during temperature abuse. Control measures to reduce the multiplication of Clostridium perfringens in foods are related to maintaining temperature control during cooling and hot-holding, reheating, or inhibitory product formulations.

Clostridioides difficile is emerging as a food-associated pathogen although outbreaks or sporadic cases have yet to be reported. It is common in animals and foods of plant and animal origin. Strains found in both foods and patients are indistinguishable, implicating food as a vehicle of transmission.

Foods may be contaminated directly and indirectly with Clostridioides difficile spores at all stages of the food chain. Handling of food, especially washing, in domestic and catering kitchens may also lead to contamination of the food preparation environment and cross-contamination. Methods for detection and enumeration in various foods are available but are not standardized and vary in effectiveness.

Experts said illnesses are likely underreported and improved surveillance is needed to determine the true global burden. Improved investigation of foodborne illness and outbreaks will enhance understanding of contributing causes and inform the development of intervention strategies to prevent further illness.

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