Which bacteria are capable of forming spores that help them survive in extreme conditions?

Correct Answer: C

Rationale: The correct answer is C, both A and B. Clostridium botulinum and Bacillus anthracis are both capable of forming spores, which are a protective mechanism that allows them to survive harsh conditions. Clostridium botulinum causes botulism and forms spores in anaerobic environments, while Bacillus anthracis causes anthrax and forms spores in aerobic environments. Therefore, both choices A and B are correct. Choice D is incorrect as it contradicts the fact that both bacteria are capable of forming spores.

Correct Answer: A

Rationale: The correct answer is A: Bordetella pertussis. This bacterium is known for causing whooping cough due to its ability to produce toxins that damage the respiratory tract, leading to severe coughing fits. Clostridium tetani causes tetanus, Haemophilus influenzae can cause respiratory infections but not whooping cough, and Staphylococcus aureus is more commonly associated with skin infections. Therefore, A is the correct choice based on its specific association with the disease in question.

Correct Answer: C

Rationale: The correct answer is C: IgA. IgA is the most prominent immunoglobulin class present in external secretions like saliva, tears, and mucus. It plays a crucial role in mucosal immunity by preventing pathogens from entering the body. IgG is mainly found in the blood and tissues, IgM is the first antibody produced in response to an infection, and IgE is involved in allergic reactions. IgA's presence in external secretions helps protect the body from infections at mucosal surfaces, making it the correct choice in this context.

Correct Answer: D

Rationale: The correct answer is D: 1-2 years. Rabies has a long incubation period before symptoms appear due to the slow progression of the virus within the body. The virus travels along nerve fibers to the brain, which can take months to years. During this time, the virus replicates and spreads, eventually leading to symptoms. Choices A, B, and C are incorrect as they underestimate the incubation period of rabies. Symptoms typically do not appear as early as 48 hours, 1 week, or 1 month after infection with the rabies virus.

Correct Answer: A

Rationale: The correct answer is A: Bubonic plague. Bubonic plague is characterized by high fever and large swollen lymph nodes (buboes). The case fatality rate in untreated cases can reach 60%. This form of plague is typically transmitted through the bite of an infected flea. B: Pneumonic plague presents with respiratory symptoms and is transmitted through respiratory droplets. C: Gastrointestinal plague is not a recognized form of plague. D: Septicemic plague is a severe form of plague where the bacteria multiply in the bloodstream. It may not always present with buboes.