A relationship in which two organisms benefit is referred to as __________.

Correct Answer: B

Rationale: The correct answer is B: mutualism. In mutualism, both organisms benefit from the relationship. This is because they provide each other with resources or services that help both parties. In contrast, commensalism (A) is a relationship where one organism benefits while the other is neither helped nor harmed. Parasitism (C) is a relationship where one organism benefits at the expense of the other. Competition (D) is a relationship where both organisms are negatively affected as they compete for limited resources. Therefore, mutualism is the correct answer as it describes a mutually beneficial relationship between two organisms.

Correct Answer: B

Rationale: The correct answer is B: mutualism. In mutualism, both organisms benefit from the relationship. This is because they provide each other with resources or services that help both parties. In contrast, commensalism (A) is a relationship where one organism benefits while the other is neither helped nor harmed. Parasitism (C) is a relationship where one organism benefits at the expense of the other. Competition (D) is a relationship where both organisms are negatively affected as they compete for limited resources. Therefore, mutualism is the correct answer as it describes a mutually beneficial relationship between two organisms.

Correct Answer: C

Rationale: Step 1: S. aureus is known to produce hemolysins, leucocidins, and enterotoxin. Step 2: S. aureus colonies usually exhibit golden-yellow pigmentation with beta-hemolytic zones. Step 3: S. aureus has developed resistance to penicillin due to the production of beta-lactamase. Step 4: Therefore, statement C is not true as S. aureus is not always sensitive to penicillin. Summary: Choices A and B are correct statements about S. aureus, while choice C is incorrect due to the increasing penicillin resistance seen in S. aureus.

Correct Answer: D

Rationale: The correct answer is D because all measures mentioned are important in preventing hospital-acquired infections. Isolating the source helps prevent the spread of infections. Isolating at-risk patients reduces their exposure. Increasing patient resistance to infections through proper hygiene and immunizations minimizes susceptibility. Each measure plays a crucial role in infection prevention, making all options correct.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria listed are capable of producing exotoxins that can cause severe diarrhea. Escherichia coli can produce toxins that lead to diarrhea. Clostridium botulinum produces a neurotoxin causing botulism, which can also result in diarrhea. Vibrio cholerae is known for producing cholera toxin, a potent exotoxin that causes severe watery diarrhea. The other choices are incorrect because each bacterium listed is capable of producing a toxin that can cause diarrhea.

Correct Answer: A

Rationale: Step 1: Mycobacterium leprae is the bacterium responsible for causing leprosy, a chronic infectious disease affecting the skin and nerves. Step 2: Neisseria gonorrhoeae causes gonorrhea, a sexually transmitted infection. Step 3: Streptococcus pneumoniae causes pneumonia and other respiratory infections. Step 4: Clostridium perfringens causes gas gangrene and food poisoning. Summary: A is correct as Mycobacterium leprae specifically causes leprosy, while B, C, and D cause different diseases unrelated to leprosy.

Correct Answer: C

Rationale: The correct answer is C: Inhibits protein synthesis. Exotoxin of C. Diphtheriae acts by inhibiting protein synthesis in host cells. This disrupts cellular functions and leads to tissue damage. Choice A is incorrect because acetylcholine release is not affected. Choice B is incorrect as it does not involve neurotransmitters. Choice D is incorrect as the exotoxin does have a specific mechanism.

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: Klebsiella pneumoniae. This bacterium is commonly associated with pneumonia in elderly patients. Klebsiella pneumoniae is a Gram-negative, non-motile, rod-shaped bacterium that frequently causes pneumonia in individuals with underlying health conditions. It is known for its ability to produce a distinctive mucoid capsule. Pseudomonas aeruginosa (B) is more commonly associated with hospital-acquired infections, particularly in immunocompromised individuals. Escherichia coli (C) is a common cause of urinary tract infections but is less likely in this case due to the symptoms and sputum sample results. Haemophilus influenzae (D) is another common respiratory pathogen, but in this scenario, Klebsiella pneumoniae is the most likely causative agent based on the patient's age, symptoms, and the characteristics of the bacteria described in the sputum sample.