After continuous treatment with antibiotics a patient got symptoms of stomatitis. Examination of specimens of oral mucous membrane revealed some oval polymorphous Gram-positive microorganisms arranged in clusters. What microorganism may be the cause of such manifestations?

Correct Answer: C

Rationale: The correct answer is C: S.aureus. Stomatitis is commonly caused by S.aureus due to its ability to form clusters of oval polymorphous Gram-positive microorganisms. S.aureus is known to colonize the oral mucous membrane and can cause infections, especially after prolonged antibiotic use. Explanation for other choices: A: С.albicans - Candida albicans is a fungus commonly associated with oral thrush, not typically causing stomatitis. B: C.perfringens - Clostridium perfringens is a bacterium associated with food poisoning and gas gangrene, not commonly causing stomatitis. D: S.pyogenes - Streptococcus pyogenes is known to cause strep throat and skin infections, but not typically associated with stomatitis.

Correct Answer: D

Rationale: The correct answer is D: rRNA. Bacterial ribosomes consist mainly of ribosomal RNA (rRNA), which plays a crucial role in protein synthesis. Ribosomes are composed of rRNA and proteins, with rRNA being the major component. rRNA serves as the structural and catalytic component of the ribosome, aiding in the binding of mRNA and tRNA during translation. Carbohydrates (A) and lipids (B) are not primary components of ribosomes, and DNA (C) is not found in ribosomes as they are involved in storing genetic information, not in protein synthesis.

Correct Answer: A

Rationale: The correct answer is A: Nucleoid. The bacterial genome is located in the nucleoid, a region within the bacterial cell where the genetic material is condensed and organized. This structure is not the same as a nucleus found in eukaryotic cells. The other choices (B: Nucleotide and C: ATP) are incorrect because nucleotide refers to a building block of DNA or RNA, and ATP is a molecule used for energy transfer in cells, neither of which specifically houses the bacterial genome. Choice D: None of the above is incorrect as well, as the correct term for the compact structure containing the bacterial genome is the nucleoid.

Correct Answer: D

Rationale: The correct answer is D: Rifampicin. Rifampicin is a first-line antibiotic for treating pulmonary tuberculosis due to its high efficacy against Mycobacterium tuberculosis. It works by inhibiting bacterial RNA synthesis. Furasolidone (A) is not commonly used for tuberculosis, Bactrim (B) is not a first-line drug for tuberculosis, and Streptocide (C) is not as effective as Rifampicin.

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: C

Rationale: The correct answer is C because chills, fever, and loss of consciousness are not typical symptoms of botulism. Botulism is characterized by descending, flaccid paralysis (choice A), dry mouth, difficulty swallowing, and speaking (choice B), and blurred vision, diplopia (choice D). These symptoms result from the neurotoxin produced by Clostridium botulinum, leading to muscle weakness and paralysis. Chills, fever, and loss of consciousness are more commonly associated with infections or other conditions, not botulism.

Correct Answer: B

Rationale: The correct answer is B: dermis. The papillary layer is located in the dermis, specifically at the junction with the epidermis. It contains capillaries, lymphatics, and sensory receptors, contributing to the skin's strength and elasticity. The epidermis (choice A) is the outermost layer of the skin, while the hypodermis (choice C) and subcutaneous layer (choice D) are deeper layers beneath the dermis, primarily composed of fat cells and connective tissue. Therefore, the papillary layer is part of the dermis, making choice B the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Neisseria meningitidis. This bacterium is a Gram-negative diplococcus commonly associated with meningitis. Neisseria meningitidis is a leading cause of bacterial meningitis in young adults and adolescents. It is known for causing fever, headache, and neck stiffness. The other choices, Streptococcus pneumoniae, Haemophilus influenzae, and Klebsiella pneumoniae, are not typically Gram-negative diplococci and are not commonly associated with the symptoms described. Streptococcus pneumoniae is a Gram-positive coccus, Haemophilus influenzae is a Gram-negative coccobacillus, and Klebsiella pneumoniae is a Gram-negative rod. Therefore, Neisseria meningitidis is the most likely causative agent in this scenario.

Correct Answer: D

Rationale: The correct answer is D: Genus Aspergillus. Aflatoxins are toxic compounds produced by certain species of fungi, particularly Aspergillus species. Aspergillus flavus and Aspergillus parasiticus are well-known producers of aflatoxins. These fungi can contaminate crops such as peanuts, corn, and tree nuts, leading to potential health risks. Cryptococcus (A), Actinomyces (B), and Streptococcus (C) are not known to produce aflatoxins. It is important to be aware of the sources and implications of aflatoxin contamination to ensure food safety and public health.