Bacteria that require oxygen for survival are called:

Correct Answer: C

Rationale: The correct answer is C: Obligate aerobes. These bacteria require oxygen for their survival and growth. They utilize oxygen in their metabolic processes and cannot survive in the absence of oxygen. Choice A, obligate anaerobes, cannot survive in the presence of oxygen. Choice B, facultative anaerobes, can switch between aerobic and anaerobic metabolism based on oxygen availability. Choice D, aerotolerant anaerobes, can tolerate the presence of oxygen but do not require it for their growth. Therefore, the most appropriate term for bacteria that require oxygen for survival is obligate aerobes.

Correct Answer: B

Rationale: The correct answer is B: abiogenesis. Spontaneous generation refers to the idea that living organisms can arise from non-living matter, which was disproven by Louis Pasteur. Abiogenesis specifically refers to the origin of life from non-living matter, making it synonymous with spontaneous generation. Biogenesis (A) is the principle that living organisms only come from other living organisms. Evolution (C) is the process of gradual change in species over time. Spontaneity (D) refers to happening without external cause and is not directly related to the concept of spontaneous generation.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is the most likely causative agent for pneumonia in this case due to the presence of Gram-positive cocci in pairs with a capsule, which is a typical characteristic of S. pneumoniae. This pathogen is a common cause of community-acquired pneumonia and is known for its encapsulated morphology. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically present in pairs with a capsule in pneumonia cases. Klebsiella pneumoniae (C) is a Gram-negative bacterium and does not match the description provided. Pseudomonas aeruginosa (D) is a Gram-negative bacterium that is not typically associated with Gram-positive cocci in pneumonia samples.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. The presence of cysts with four nuclei is characteristic of Entamoeba histolytica, a protozoan parasite causing amoebic dysentery. It forms cysts with four nuclei before maturing into trophozoites. Balantidium coli (B) is a ciliated protozoan causing balantidiasis, not known for four-nuclei cysts. Giardia lamblia (C) forms cysts with two nuclei, causing giardiasis. Trichomonas hominis (D) is a non-pathogenic flagellate found in the human colon, not associated with four-nuclei cysts.

Correct Answer: A

Rationale: The likely diagnosis is Meningococcal meningitis (Choice A) due to the presence of Gram-negative diplococci in the cerebrospinal fluid. Neisseria meningitidis is a Gram-negative diplococcus commonly associated with meningococcal meningitis. Fever, chills, and neck stiffness are classic symptoms of bacterial meningitis, and Neisseria meningitidis often presents with these symptoms. Pneumococcal meningitis (Choice B) is caused by Streptococcus pneumoniae, a Gram-positive organism. Haemophilus influenzae (Choice C) is also a Gram-negative organism but typically presents with a different clinical picture. Listeria monocytogenes (Choice D) is a Gram-positive rod and is more commonly associated with meningitis in neonates, elderly, and immunocompromised individuals.