It's important to understand that there are no bacteria that cannot cause foodborne illness. Even bacteria that are generally considered beneficial, like those found in fermented foods, can cause illness under certain circumstances.

Here's why:

* Virulence factors: Bacteria possess genes that code for virulence factors. These factors determine their ability to cause disease, like toxins, adhesion factors, or invasion mechanisms. While some bacteria may have low virulence, they can still cause illness in susceptible individuals.

* Environmental factors: Factors like temperature, pH, oxygen availability, and the presence of other bacteria can influence a bacterium's ability to grow and become pathogenic.

* Individual susceptibility: Individuals have varying immune systems and sensitivities. A bacterium that may cause mild illness in one person could lead to severe illness in another.

Examples:

* Lactobacillus: These are commonly used in fermented foods, but some strains have been linked to infections in individuals with weakened immune systems.

* Bifidobacterium: Another genus commonly found in probiotics, but some species can be opportunistic pathogens.

* E. coli: While some strains are harmless, others are known for causing severe food poisoning.

In conclusion: It's crucial to practice safe food handling and preparation to minimize the risk of foodborne illness from any bacterial source. Don't rely on the idea of "safe bacteria" as a guarantee of safety.