Which statement related to the mumps vaccine is true:

Correct Answer: D

Rationale: The correct answer is D: it is a live attenuated vaccine. This is true because the mumps vaccine is indeed a live attenuated vaccine, meaning it contains a weakened form of the virus to stimulate an immune response without causing the disease. This type of vaccine provides long-lasting immunity. A, B, and C are incorrect: A: the vaccine is recommended, not obligatory - this is incorrect because the mumps vaccine is typically recommended for all individuals to prevent the spread of the disease. B: the vaccine is not given in combination with other vaccines - this is incorrect as the mumps vaccine is often given in combination with measles and rubella vaccines as the MMR vaccine. C: the vaccine is administered orally - this is incorrect because the mumps vaccine is usually administered via injection, not orally.

Correct Answer: A

Rationale: The correct answer is A: Ziehl-Neelsen staining method. This method is used to detect acid-fast bacteria like Mycobacterium tuberculosis. Step-by-step rationale: 1. Acid-fast bacteria resist decolorization with acid-alcohol. 2. The red bacilli seen in the smear indicate acid-fast bacteria. 3. Ziehl-Neelsen stain uses carbol fuchsin to stain acid-fast bacteria red. 4. The blue background is likely the counterstain methylene blue. Incorrect choices: B: Gram stain is for categorizing bacteria into Gram-positive or Gram-negative, not specific for acid-fast bacteria. C: Giemsa stain is used for blood films and detecting parasites, not acid-fast bacteria. D: Neisser stain is not a standard microbiological staining method.

Correct Answer: A

Rationale: Correct Answer: A Rationale: 1. Enteropathogenic E. coli (EPEC) attach to enterocytes via a type III secretion system. 2. Once attached, they form attaching and effacing lesions on the microvilli, leading to microvillus destruction. 3. This mechanism allows EPEC to cause diarrhea by disrupting the normal absorptive function of the intestines. Summary: - B (They are invasive and produce enterotoxin) is incorrect because EPEC are non-invasive and do not produce enterotoxins. - C (Cause disease clinically similar to bacterial) is vague and does not provide specific information about EPEC pathogenesis. - D (None of the above) is incorrect as A is the correct explanation for EPEC pathogenicity.

Correct Answer: A

Rationale: The correct answer is A: Clostridia. Fusiform spore-forming microorganisms that stain violet-blue with Gram's stain are characteristic of Clostridia. Clostridia are anaerobic, rod-shaped bacteria known for their ability to form spores and cause diseases such as tetanus and botulism. Summary of other choices: B: Streptococci are spherical, not fusiform, and typically do not form spores. C: Spirochaete are spiral-shaped bacteria and do not typically form spores. D: Actinomycete are filamentous bacteria that do not typically form spores and do not stain violet-blue with Gram's stain.

Correct Answer: A

Rationale: The correct answer is A: Protein synthesis. Bacterial ribosomes are responsible for translating mRNA into proteins through a process called translation. This is a crucial step in gene expression, where amino acids are assembled into polypeptide chains. Choice B (DNA replication) is incorrect because ribosomes are not involved in DNA replication. Choice C (Flagella formation) is incorrect as ribosomes do not play a direct role in flagella formation. Choice D (Toxin production) is incorrect as ribosomes are not directly involved in producing toxins.