Infections of CNS can be caused by:

Correct Answer: D

Rationale: The correct answer is D because all three choices, Clostridium botulinum, Morbillivirus morbillorum, and Clostridium tetani, can cause infections of the central nervous system (CNS). Clostridium botulinum can lead to botulism, which affects the nervous system. Morbillivirus morbillorum can cause measles, which can lead to viral encephalitis. Clostridium tetani can cause tetanus, which affects the CNS by producing neurotoxins. Therefore, all three choices are pathogens that can cause infections of the CNS.

Correct Answer: A

Rationale: Rationale: Bacillus cereus is associated with food intoxication due to its ability to produce toxins that cause gastrointestinal symptoms. B. subtilis is not known to cause food intoxication. B. anthracis causes anthrax, not food intoxication. Option D is incorrect as not all Bacillus species cause food intoxication.

Correct Answer: D

Rationale: The correct answer is D because antigenic shift is a major change in the influenza virus where genetic material from different influenza viruses mix to create a new subtype. This is a large-scale change that results in a novel virus with a different antigenic composition. Option A and B are incorrect because antigenic shift does involve the exchange of genetic information between animal and human influenza A viruses, and it does occur when animal or avian influenza viruses of type A directly pass into the human population. Option C is incorrect because antigenic shift is not related to the recirculation of a previously circulating influenza strain.

Correct Answer: D

Rationale: The correct answer is D: Gram-negative coccobacillus. Francisella tularensis is a Gram-negative coccobacillus because it has a unique shape that is between a coccus (spherical) and a bacillus (rod-shaped) and it stains pink/red in the Gram staining process. It is important to note that it is not a coccus (choice B) or a Gram-positive bacterium (choice A). Choice C is too general and does not specify the coccobacillus shape of F. tularensis. So, the correct answer is D due to its specific characteristics as a Gram-negative coccobacillus.

Correct Answer: D

Rationale: The correct answer is D: Protoplast. Lipopolysaccharides of Gram-negative bacteria consist of three main components: O-specific polysaccharide chain, R-specific polysaccharide chain, and Lipid A. Protoplast is not a component of lipopolysaccharides. O-specific polysaccharide chain is responsible for serotype specificity, R-specific polysaccharide chain varies among strains, and Lipid A is the endotoxin component. Protoplast refers to a bacterial cell devoid of a cell wall, which is not a component of lipopolysaccharides.