Which of the following are examples of psychotropic bacteria?

B is the correct answer because Yersinia, particularly Yersinia pestis which causes plague, and Listeria monocytogenes, which is known for its serious health implications during pregnancy and for immunocompromised individuals, are both significant pathogens in the context of foodborne illnesses and can affect mental health due to physical health stressors. Clostridium, particularly species such as Clostridium botulinum, produces potent neurotoxins that can impact neurological function and promote serious psychological stress due to the severity of the illnesses they cause.

In contrast, the other choices feature bacteria that are notable for their roles in food safety and foodborne illness, but they do not specifically relate to psychotropic effects. For example, while Salmonella and E. coli are well-known for causing gastrointestinal disturbances, they are less associated with psychotropic effects directly, focusing instead on physical health consequences. Each of the other options includes a mix of common foodborne pathogens that primarily affect physical health rather than having a direct impact on psychological conditions.