Routine investigation of microbiological sanitary condition of air in a hospital is performed once in 3 months. What microorganism is the sanitary indicator of air condition in an enclosed space?

Correct Answer: D

Rationale: The correct answer is D: P.aeruginosa. This bacterium is commonly found in water and soil, making its presence in indoor air an indicator of poor sanitation. Step 1: P.aeruginosa is an opportunistic pathogen known to cause infections in hospitals. Step 2: Its presence in the air indicates potential contamination and poor air quality. Step 3: Regular monitoring of P.aeruginosa levels can help assess the effectiveness of sanitation measures. Summary: A, B, and C are not suitable indicators of air sanitation in an enclosed space as they are not typically associated with environmental contamination or poor air quality.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria listed (Staphylococcus aureus, Escherichia coli, Clostridium botulinum) can produce toxins leading to food poisoning. Staphylococcus aureus produces heat-stable toxins causing rapid onset of symptoms. Escherichia coli can produce toxins like Shiga toxin leading to severe foodborne illness. Clostridium botulinum produces neurotoxins causing botulism. Choice A, B, and C are incorrect because each bacteria can produce toxins that are harmful if ingested.

Correct Answer: C

Rationale: The correct answer is C: rotaviruses. Rotaviruses are the most common cause of infectious diarrhea in infants and children due to their highly contagious nature and ability to spread easily in childcare settings. They are known to cause severe diarrhea, vomiting, and dehydration in young children. Noroviruses (A), adenoviruses (B), and caliciviruses (D) can also cause diarrhea, but rotaviruses are specifically known for their prevalence and severity in the pediatric population. This is why C is the correct answer.

Correct Answer: A

Rationale: The correct answer is A: TRUE. The structures and organs listed are indeed part of the immune system. The lymphatic system transports lymph, lymphoid tissue contains immune cells, lymph nodes filter lymph, thymus matures T-cells, and spleen filters blood and produces immune cells. This comprehensive network is crucial for defending the body against pathogens. Choice B is incorrect as all listed structures are components of the immune system. Choice C is also incorrect as the statement is universally true, not situational. Choice D is incorrect as the correct answer is A.

Correct Answer: B

Rationale: The correct answer is B because the structure of the cytoplasmic membrane in gram-positive and gram-negative bacteria is fundamentally different. Gram-positive bacteria have a single-layered cytoplasmic membrane, while gram-negative bacteria have a double-layered cytoplasmic membrane with an additional outer membrane. This key difference is crucial for various functions such as antibiotic resistance and nutrient transport. Rationale for the incorrect choices: A: Gram-positive bacteria have a single-layered cytoplasmic membrane, not a double-layered one. C: Prokaryotes do have a cytoplasmic membrane, which is essential for maintaining cell integrity and regulating the passage of molecules. D: Gram-negative bacteria have a double-layered cytoplasmic membrane, not a three-layered one.

Correct Answer: C

Rationale: The correct answer is C: Negative stain. Negative staining uses acidic dyes which are repelled by the bacterial cell wall components, highlighting bacteria with a large amount of peptidoglycan. Acid-fast stain (A) is used to identify Mycobacterium species with waxy cell walls. Gram stain (B) differentiates bacteria into Gram-positive and Gram-negative based on cell wall composition. Option D is a duplicate of option C and is incorrect.

Correct Answer: A

Rationale: Passive immunity is the transfer of pre-formed antibodies from one individual to another, providing immediate protection. This process does not involve the recipient's immune response, hence it is called passive. Active immunity, on the other hand, involves the individual's immune system producing its own antibodies after exposure to an antigen. Innate immunity refers to the body's natural defense mechanisms present from birth, not involving antibodies. Therefore, the correct answer is A: passive immunity.

Correct Answer: D

Rationale: The correct answer is D because enveloped viruses have a lipid bilayer envelope derived from the host cell membrane, which is a complex structure, not exhibiting any specific symmetry. Choice A (cubic symmetry) is incorrect as enveloped viruses do not have any specific geometric shape. Choice B (spiral symmetry) is incorrect as this type of symmetry is typically seen in non-enveloped viruses like helical viruses. Choice C (complex symmetry) is also incorrect as enveloped viruses do not exhibit a specific symmetrical pattern. Therefore, the correct answer is D because enveloped viruses do not have a defined symmetry and can vary in shape and structure.

Correct Answer: A

Rationale: The correct answer is A: Toxin production test. Rationale: 1. Diphtheria is caused by a toxin produced by Corynebacterium diphtheriae. 2. To confirm if the carrier is dangerous, we need to test if they are producing the toxin. 3. The toxin production test directly assesses if the bacteria are producing the harmful toxin. 4. Positive results indicate the carrier is dangerous and can transmit the disease to others. Summary of other choices: B: Mouse neutralization test - Used to detect diphtheria antitoxin levels in blood, not to confirm if the carrier is dangerous. C: Immunofluorescence test - Used to detect specific antigens or antibodies, not directly related to confirming the carrier's danger. D: Complement fixation test - Measures immune response, not specific to toxin production confirmation.