How soon after a potentially infectious bite should a person be treated for rabies?

Correct Answer: B

Rationale: The correct answer is B: Within 24 hours. Rabies post-exposure prophylaxis should ideally be initiated as soon as possible after a potentially infectious bite to prevent the virus from spreading and causing symptoms. Immediate treatment is crucial to prevent the virus from reaching the central nervous system. Waiting beyond 24 hours increases the risk of the virus reaching the brain and becoming fatal. Choices A, C, and D are incorrect because waiting for 6 months, a week, or 2 weeks respectively would significantly delay treatment, allowing the virus to progress and potentially become untreatable.

Correct Answer: A

Rationale: The correct answer is A: Bacteria. Urinary tract infections (UTIs) are primarily caused by the invasion of bacteria into the urinary tract. Bacteria, especially Escherichia coli (E. coli), are the most common culprits. They enter the urinary tract through the urethra and can multiply in the bladder, leading to infection. Viruses (choice B) and fungi (choice C) are not typical causes of UTIs. "None of the above" (choice D) is incorrect as bacteria are indeed the main cause of UTIs.

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: 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: A

Rationale: Rationale: 1. Epstein-Barr virus causes infectious mononucleosis due to primary infection. 2. Certain types of cancer, such as Burkitt lymphoma and nasopharyngeal carcinoma, are associated with Epstein-Barr virus through oncogenic mechanisms. 3. Chickenpox and shingles are caused by varicella-zoster virus (HHV3). 4. Roseola infantum is caused by human herpesvirus 6 (HHV6). Summary: Choice A is correct as Epstein-Barr virus is linked to infectious mononucleosis and specific cancers. Choices B, C, and D are incorrect as they are caused by different herpesviruses.

Correct Answer: D

Rationale: The correct answer is D: Binary fission. Binary fission is a method of bacterial cell division, not a method of acquiring genetic material. Transformation, conjugation, and transduction are mechanisms through which bacteria can acquire genetic material from other sources. Transformation involves the uptake of naked DNA from the environment, conjugation is the transfer of genetic material through direct cell-to-cell contact, and transduction is the transfer of genetic material via bacteriophages. Therefore, binary fission is the only option that does not involve the acquisition of new genetic material.

Correct Answer: D

Rationale: The correct answer is D (All of the above) as all three bacteria (Escherichia coli, Salmonella enterica, Neisseria meningitidis) produce endotoxins causing fever and shock. Endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria and can trigger an immune response leading to fever and shock. Escherichia coli and Salmonella enterica are common causes of food poisoning and sepsis, while Neisseria meningitidis is responsible for meningococcal meningitis and septicemia. Therefore, all three choices are correct in producing endotoxins that can cause fever and shock.

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: 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.