A bacteriological laboratory has been investigating a sample of homemade dried fish that was the cause of severe food poisoning. Microscopy of the culture inoculated in Kitt-Tarozzi medium revealed microorganisms resembling a tennis racket. What diagnosis can be made?

Correct Answer: A

Rationale: The correct answer is A: Botulism. The tennis racket appearance seen under the microscope is characteristic of Clostridium botulinum, the bacterium responsible for botulism. This bacterium produces spores that resemble a tennis racket shape. Botulism is a type of food poisoning caused by the ingestion of the toxin produced by Clostridium botulinum. Summary: B: Salmonellosis is caused by Salmonella bacteria, which do not exhibit a tennis racket appearance. C: Cholera is caused by Vibrio cholerae, which also does not resemble a tennis racket under the microscope. D: Dysentery is typically caused by bacteria such as Shigella or Entamoeba histolytica, neither of which exhibit the characteristic tennis racket appearance.

Correct Answer: D

Rationale: The correct answer is D: Adenovirus. Adenovirus commonly causes acute febrile pharyngitis and pharyngoconjunctival fever. Adenovirus is known to cause respiratory infections and can present with symptoms such as sore throat, fever, and conjunctivitis. VZV (Varicella-Zoster Virus) causes chickenpox and shingles, not these specific symptoms. Measles virus causes a systemic illness with characteristic rash, not typically pharyngitis. Rubella virus causes a mild febrile illness with rash, but not pharyngitis. Therefore, based on the clinical presentation described, adenovirus is the most likely cause.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is known for producing a capsule that helps it evade the immune system. The capsule acts as a protective barrier, making it difficult for the immune system to recognize and attack the bacteria. Streptococcus pneumoniae is a common cause of pneumonia and meningitis. Explanation for why other choices are incorrect: B: Escherichia coli does not typically produce a capsule for immune evasion. It is more commonly associated with gastrointestinal infections. C: Salmonella enterica also does not produce a capsule for immune evasion. It is known for causing foodborne illness. D: Bacillus subtilis is a soil bacterium that is not known for producing a capsule to avoid the immune system.

Correct Answer: A

Rationale: Step 1: Treponema pallidum is a spirochete bacterium known to cause syphilis. Step 2: It is sexually transmitted and can cause various stages of disease. Step 3: Neisseria gonorrhoeae causes gonorrhea, not syphilis. Step 4: Chlamydia trachomatis causes chlamydia, not syphilis. Step 5: Escherichia coli is a common gut bacterium and not responsible for syphilis. Treponema pallidum is the correct answer as it is the specific bacterium known to cause syphilis.

Correct Answer: A

Rationale: The correct answer is A: Mycobacterium tuberculosis. 1. Bright-red acid-resistant bacilli indicate the presence of mycolic acids in the cell wall, characteristic of Mycobacterium species. 2. Found in groups or singularly suggests the clumping nature of acid-fast bacilli. 3. Growth appearing after 10-15 days on nutrient media is consistent with the slow growth rate of Mycobacterium tuberculosis. 4. Yersinia pseudotuberculosis (B) and Klebsiella rhinoscleromatis (D) are not acid-fast bacilli and do not match the growth characteristics described. 5. Histoplasma dubrosii (C) is a fungus, not a bacterium, and does not exhibit acid-fast staining or the described growth pattern.

Correct Answer: A

Rationale: Step 1: Clostridia of tetanus, botulism, anaerobic gas infection are spore-forming bacteria. Step 2: Spores are resistant structures that allow bacteria to survive in harsh conditions. Step 3: Feces contain these spore-forming bacteria due to contamination. Step 4: When feces are deposited on soil, the spores of these bacteria enter the soil. Step 5: Spores can remain dormant in soil for long periods. Summary: Choice A is correct as spore-forming bacteria enter soil through feces, which act as a source of contamination. Choices B, C, and D are incorrect as they do not involve the direct introduction of spores into soil like feces do.

Correct Answer: B

Rationale: The correct answer is B: pharmacokinetics. Pharmacokinetics is the study of drug movement in the body, including absorption, distribution, metabolism, and excretion. It focuses on how the body processes a drug over time. Pharmacodynamics (A) is the study of the effects drugs have on the body. Pharmacotherapeutics (C) involves using drugs to treat diseases. Pharmacy (D) is the practice of preparing and dispensing medications. Pharmacokinetics specifically deals with drug concentrations at different body sites after administration, making it the most appropriate choice for this question.

Correct Answer: A

Rationale: Rationale: 1. Salmonella typhi causes typhoid fever, which can lead to intestinal infections. 2. Shigella flexneri causes dysentery, primarily affecting the colon. 3. Helicobacter pylori causes stomach ulcers, not intestine infections. Summary: A is correct as Salmonella typhi causes intestine infection. B and C are incorrect as they cause different gastrointestinal issues. D is incorrect as A is a valid choice.

Correct Answer: B

Rationale: The correct answer is B because retroviruses, including those in the Family Retroviridae, have a capsid consisting of two copies of single-stranded RNA (ssRNA). This is a defining characteristic of retroviruses, which use reverse transcriptase to convert their ssRNA into DNA. This DNA is then integrated into the host cell's genome. Choices A, C, and D are incorrect because Family Retroviridae viruses are not helical non-enveloped viruses (C), they are not helical enveloped viruses (A), and they do not have a complex type of symmetry (D).