The primary mode of action of aminoglycosides is to:

Correct Answer: A

Rationale: Aminoglycosides primarily inhibit protein synthesis by binding to the 30S ribosomal subunit in bacteria. This action leads to misreading of mRNA and ultimately disrupts the translation process, resulting in faulty protein production and bacterial cell death. Incorrect choices: B: Aminoglycosides do not inhibit DNA replication. C: Aminoglycosides do not disrupt cell membrane integrity. D: Aminoglycosides do not inhibit folic acid synthesis. In summary, the correct choice (A) aligns with the known mechanism of action of aminoglycosides, making it the most appropriate answer.

Correct Answer: C

Rationale: The correct answer is C because diphtheria exotoxin is absorbed into the underlying healthy tissues and spreads throughout the body. This is due to the toxin's ability to enter the bloodstream and target various organs, causing systemic effects. Choice A is incorrect as the toxin does not stay localized at the site of infection. Choice B is incorrect as diphtheria exotoxin does not directly affect neuro-muscular transmission. Choice D is also incorrect as the toxin does spread throughout the body.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Anopheles mosquitoes are the primary vectors for transmitting malaria. 2. They prefer stagnant water for breeding, common in tropical regions. 3. Culex mosquitoes primarily spread diseases like West Nile virus. 4. Aedes mosquitoes transmit diseases like Zika and dengue fever. 5. Mansonia mosquitoes are known for transmitting filarial diseases. Therefore, the correct answer is A (Anopheles), as they are specifically associated with spreading malaria.

Correct Answer: C

Rationale: The correct answer is C: All microorganisms. Sterilization aims to eliminate all microorganisms, including pathogenic and non-pathogenic ones, to ensure complete absence of viable organisms. This is crucial in medical, laboratory, and food preparation settings to prevent contamination and spread of infections. Choices A and B are incorrect because sterilization does not differentiate between pathogenic and non-pathogenic microorganisms, aiming to eradicate all. Choice D is incorrect as sterilization does involve releasing subjects (microorganisms) using physical methods.

Correct Answer: C

Rationale: The correct answer is C (25°C) because dimorphic fungi typically grow as molds at lower temperatures. At 25°C, the fungus is likely in its mold phase, which is the preferred temperature range for mold growth. Choices A, B, and D are incorrect because 15°C and 20°C are too low for optimal mold growth, and 37°C is too high as it typically favors the yeast phase of dimorphic fungi. Therefore, the preferred temperature for mold growth of a dimorphic fungus is 25°C.

Correct Answer: C

Rationale: Rationale: 1. Both Clostridium botulinum and Bacillus anthracis are known to form spores. 2. Spore formation is a mechanism for survival in harsh conditions. 3. Both bacteria are capable of causing severe diseases in humans. Summary: - Choice A and B are incorrect because each bacteria listed is capable of spore formation. - Choice D is incorrect as both bacteria mentioned can form spores to survive extreme conditions.

Correct Answer: D

Rationale: The correct answer is D: BSL4. Ebola viruses are highly infectious and pose a high risk to laboratory workers. BSL4 facilities are designed to handle agents that pose a severe threat to human health and have no available vaccines or treatments. These facilities have strict guidelines for handling infectious agents, including full-body suits, negative air pressure, and decontamination processes to prevent any possible exposure. BSL1, BSL2, and BSL3 are not adequate for handling Ebola viruses due to their lower levels of containment and safety measures.

Correct Answer: B

Rationale: The correct answer is B: Escherichia coli. E. coli is a common bacterium found in the gastrointestinal tract and is a leading cause of UTIs. It has specific virulence factors that enable it to adhere to and infect the urinary tract. Salmonella enterica causes food poisoning, Vibrio cholerae causes cholera, and Streptococcus pyogenes causes strep throat and skin infections, not UTIs. Therefore, B is the correct answer as it is the only bacterium known for causing UTIs.

Correct Answer: D

Rationale: The correct answer is D: Gram-negative bacteria without peptidoglycan. Chlamydia is an intracellular, gram-negative bacteria that lacks peptidoglycan in its cell wall. Peptidoglycan is a key component of the cell wall in most bacteria, but Chlamydia has a unique structure without it. This makes it different from choices A, B, and C, which describe characteristics not applicable to Chlamydia. Choice A is incorrect because Chlamydia is not a gram-positive coccobacteria. Choice B is incorrect because Chlamydia does have a cell wall, albeit lacking peptidoglycan. Choice C is incorrect because Chlamydia is not a gram-negative bacteria with little peptidoglycan, but rather without it.