The five people are currently on respirators - the toxin impairs nerve signals to the lungs.
Pesto is an oil based mixture of basil, garlic, parmesan cheese, pine nuts and olive oil. It is generally prepared fresh and kept refrigerated. The pH would tend towards neutral because there are no acidulants. Oil mixtures provide an anaerobic environment. So the combination of a more neutral pH and an low oxygen environment are conditions that allow C. botulinum to grow if the temperature is right and other organisms don't outcompete it. So where one would have problems is when this is temperature abused.
Pesto is an oil based mixture of basil, garlic, parmesan cheese, pine nuts and olive oil. It is generally prepared fresh and kept refrigerated. The pH would tend towards neutral because there are no acidulants. Oil mixtures provide an anaerobic environment. So the combination of a more neutral pH and an low oxygen environment are conditions that allow C. botulinum to grow if the temperature is right and other organisms don't outcompete it. So where one would have problems is when this is temperature abused.
In the US Food Code, oil-based mixtures such as garlic in oil are considered TCS foods (Temperature Control for Safety). For operations wanting to sell such products, there would need to something called a secondary barrier to prevent growth. The first barrier is refrigeration. But as with this case, there needs to be something there to prevent growth if the product is temperature abused. This could be an antimicrobial compound or an acidulent to lower the pH.
BBC
https://www.bbc.com/news/articles/c1epwqln5e3o
Pesto linked to botulism cases in France
Michelle Roberts
Digital health editor, BBC News
Sept 11, 2024