Nokea
A laboratory received a food product that had been taken from the focus of food poisoning and presumably contained botulinum toxin. To identify the type of toxin, the neutralization reaction must be performed on white mice. What biological product is used in this reaction?
- A. Antitoxic serum
- B. Normal serum
- C. Antibacterial serum
- D. Diagnosticum
Correct Answer: A
Rationale: The correct answer is A: Antitoxic serum. In the neutralization reaction to identify botulinum toxin, antitoxic serum is used to neutralize the toxin in white mice. Antitoxic serum contains antibodies that specifically target and neutralize the botulinum toxin. Normal serum (B) does not contain the necessary antibodies to neutralize the toxin. Antibacterial serum (C) is not effective against toxins like botulinum. Diagnosticum (D) is a general term and does not specifically refer to the biological product required for this reaction.
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Which of the following lack nucleic acids?
- A. Archaea
- B. Viruses
- C. Prions
- D. Bacteria
Correct Answer: C
Rationale: The correct answer is C: Prions. Prions are infectious proteins that lack nucleic acids, such as DNA or RNA, which are essential components of all other living organisms, including Archaea, Bacteria, and Viruses. Prions are unique in their ability to cause protein misfolding and aggregation in the brain, leading to various neurodegenerative diseases. The other choices (A: Archaea, B: Viruses, D: Bacteria) all contain nucleic acids in the form of DNA or RNA, making them distinct from prions. Therefore, C is the correct answer in this case.
Gram (+) bacteria ... MG-ribonucleate and Mg. deoxyribonucleate in:
- A. Proportion 4:1
- B. Proportion 2:1
- C. Proportion 8:1
- D. Proportion 1:1
Correct Answer: A
Rationale: The correct answer is A, proportion 4:1. Gram (+) bacteria have a higher ratio of MG-ribonucleate to Mg. deoxyribonucleate because ribosomal RNA is more abundant in actively growing bacterial cells. This higher proportion of MG-ribonucleate to Mg. deoxyribonucleate is essential for protein synthesis and growth. The other choices are incorrect because they do not reflect the higher ratio of ribosomal RNA to DNA in Gram (+) bacteria, which is crucial for their metabolic activities and cellular functions.
A patient with abdominal pain had a stool culture revealing non-lactose-fermenting, Gram-negative rods that produced gas in a nutrient broth. What is the most likely causative agent?
- A. Salmonella typhi
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: D
Rationale: The correct answer is D: Proteus vulgaris. This is because Proteus species are non-lactose-fermenting Gram-negative rods that are known to produce gas in nutrient broths. Proteus vulgaris is commonly associated with urinary tract infections and can also cause abdominal infections.
A: Salmonella typhi typically causes typhoid fever and is not known to produce gas in nutrient broths.
B: Shigella dysenteriae is a causative agent of dysentery and does not typically produce gas in nutrient broths.
C: Escherichia coli is a lactose-fermenting bacterium and does not fit the description of the organism in the stool culture.
Which toxin is specific for ETEC:
- A. TSST-1
- B. Shiga-like toxin
- C. Erythrogenic toxin
- D. LT enterotoxin
Correct Answer: D
Rationale: The correct answer is D: LT enterotoxin. This toxin is specific for Enterotoxigenic E. coli (ETEC) and is responsible for causing diarrhea by increasing cyclic AMP levels in intestinal cells. TSST-1 (choice A) is produced by Staphylococcus aureus, not ETEC. Shiga-like toxin (choice B) is produced by Shigella and EHEC, not ETEC. Erythrogenic toxin (choice C) is produced by Streptococcus pyogenes, not ETEC. Therefore, the LT enterotoxin is the specific toxin associated with ETEC.
The drug most often used in fighting protozoan infections of the reproductive system is:
- A. ampicillin
- B. tetracycline
- C. ciprofloxacin
- D. metronidazole
Correct Answer: D
Rationale: The correct answer is D: metronidazole. Metronidazole is specifically effective against protozoan infections due to its ability to target and disrupt the DNA of the parasites. It is commonly used to treat infections such as trichomoniasis and giardiasis that affect the reproductive system. Ampicillin (A) and tetracycline (B) are antibiotics that target bacteria, not protozoa. Ciprofloxacin (C) is also an antibiotic that is effective against certain bacterial infections but not protozoan infections. Therefore, metronidazole is the most appropriate choice for fighting protozoan infections of the reproductive system.