What type of bacteria is responsible for the formation of acid in the stomach?

Correct Answer: B

Rationale: The correct answer is B: Helicobacter pylori. This bacterium is responsible for stomach acid formation by producing an enzyme called urease, which converts urea into ammonia and carbon dioxide, leading to an increase in stomach pH. Staphylococcus aureus (A) does not cause stomach acid formation. Bacillus cereus (C) and Clostridium botulinum (D) are not involved in stomach acid processes.

Correct Answer: B

Rationale: The correct answer is B: Jenner. Edward Jenner is credited with performing the first successful vaccination against smallpox in 1796. He used cowpox virus to inoculate individuals, leading to immunity against smallpox. Jenner's experiment laid the foundation for modern vaccination. Pasteur (A) is known for developing the germ theory of disease. Semmelweis (C) advocated for handwashing to prevent infections. Koch (D) identified the causative agents of several diseases but did not develop the smallpox vaccine.

Correct Answer: B

Rationale: The correct answer is B: Mycobacterium leprae. This bacterium is responsible for causing leprosy, also known as Hansen's disease. Mycobacterium leprae specifically targets the skin, peripheral nerves, and mucosa of the upper respiratory tract. It is an acid-fast bacterium with a slow growth rate, making it difficult to culture in the laboratory. Streptococcus pyogenes (choice A) is responsible for various infections such as strep throat, Neisseria gonorrhoeae (choice C) causes gonorrhea, and Escherichia coli (choice D) is commonly found in the gut and can lead to various infections but not leprosy.

Correct Answer: B

Rationale: The correct answer is B: Outer membrane containing lipopolysaccharides. Gram-negative bacteria have an outer membrane that contains lipopolysaccharides, which are important for protection and pathogenicity. This outer membrane is a unique feature of Gram-negative bacteria and is not present in Gram-positive bacteria, making it a key characteristic. A: Incorrect because Gram-negative bacteria have a thin peptidoglycan layer compared to Gram-positive bacteria. C: Incorrect because teichoic acids are a characteristic of Gram-positive bacteria, not Gram-negative bacteria. D: Incorrect because all bacteria, including Gram-negative bacteria, have a cell wall.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. This is because Pseudomonas aeruginosa is a common Gram-negative rod that is a non-lactose fermenter and a common cause of severe pneumonia, especially in immunocompromised individuals. It is also known for its resistance to many antibiotics, making it difficult to treat. Summary of other choices: B: Escherichia coli is a lactose fermenter and is not commonly associated with severe pneumonia. C: Klebsiella pneumoniae is a lactose fermenter and is more commonly associated with pneumonia in alcoholics or debilitated patients. D: Enterobacter cloacae is a lactose fermenter and is not a common cause of severe pneumonia.