Which of the following stains is the most widely used differential stain in hematology laboratories?

Correct Answer: D

Rationale: The correct answer is D: Kinyoun stain. This stain is the most widely used differential stain in hematology labs because it is specifically designed for acid-fast bacteria like Mycobacterium tuberculosis. It differentiates these bacteria from others based on their cell wall composition. Carbolfuchsin stain (A) is used for acid-fast bacteria in microbiology. Wright's stain (B) is used for blood cell morphology. Ziehl-Neelsen stain (C) is also used for acid-fast bacteria but is less commonly used compared to Kinyoun stain in hematology labs.

Correct Answer: B

Rationale: The function of bacterial pili is to aid in adhesion. Pili are hair-like structures on the bacterial surface that help the bacteria attach to surfaces or other cells. This adhesion is crucial for colonization and infection. Pili do not provide motility, as that is typically done by flagella. Bacteria form spores for survival under harsh conditions, and protein synthesis is carried out by ribosomes, not pili. Thus, the correct answer is B, aiding in adhesion.

Correct Answer: C

Rationale: The correct answer is C: Streptococcus pyogenes. This bacterium is commonly known as "flesh-eating bacteria" due to its ability to cause severe tissue destruction and necrotizing fasciitis. Streptococcus pyogenes produces toxins that break down skin and muscle tissues. Staphylococcus aureus (A) can cause skin infections but is not typically associated with necrotizing fasciitis. Staphylococcus epidermidis (B) is a normal skin flora and rarely causes infections. Propionibacterium acnes (D) is associated with acne and not known for causing tissue destruction. Therefore, the correct choice is Streptococcus pyogenes due to its unique ability to cause severe tissue damage and necrotizing fasciitis.

Correct Answer: C

Rationale: Step 1: Togaviridae is a family of viruses known to have non-segmented (+)ssRNA as their genetic material. Step 2: The positive sense RNA means that the viral RNA can be directly translated into proteins by host machinery. Step 3: This RNA genome acts as mRNA, allowing for immediate translation of viral proteins. Step 4: Therefore, choice C is correct as it accurately describes the genetic nature of Togaviridae. Summary: - Choice A is incorrect because Togaviridae viruses do not have helical symmetry. - Choice B is incorrect because Togaviridae viruses do not have non-segmented (-)dsRNA. - Choice D is incorrect because Togaviridae viruses are enveloped viruses.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This is because the bacterium is Gram-positive cocci in pairs, catalase-negative, and alpha-hemolytic, which are characteristic features of S. pneumoniae. The other choices can be ruled out based on specific characteristics: B) Staphylococcus aureus is catalase-positive, C) Enterococcus faecalis is gamma-hemolytic, and D) Neisseria gonorrhoeae is a Gram-negative diplococcus. Therefore, based on the given information, S. pneumoniae is the most likely causative agent of the sepsis.

Correct Answer: B

Rationale: The correct answer is B: All are correct. Candida albicans can cause skin infections such as candidiasis. Staphylococcus aureus and Streptococcus pyogenes are common bacteria that can also cause skin infections. Therefore, choice B is correct as all three microorganisms listed can cause skin infections. Choices A, C, and D are incorrect because individually, each of the microorganisms listed can cause skin infections.

Correct Answer: A

Rationale: The correct answer is A: Tuberculin. In this clinical scenario, the patient presents with symptoms suggestive of tuberculosis, including chronic cough, night sweats, weight loss, and hemoptysis. The Mantoux test, also known as the tuberculin skin test, is used to screen for tuberculosis. Tuberculin, a purified protein derivative (PPD) derived from Mycobacterium tuberculosis, is injected intradermally. The test elicits a delayed-type hypersensitivity reaction in individuals who have been exposed to the organism in the past. A positive Mantoux test indicates exposure to tuberculosis and does not differentiate between active infection and prior exposure. Explanation for other choices: B: Measles - Measles is a viral infection that presents with a characteristic rash and fever, not consistent with the symptoms described in the case. C: Tetanus and diphtheria toxoids vaccine (Td) - Td vaccine is not used for tuberculosis screening and does not elicit

Correct Answer: D

Rationale: After the transfer of the F plasmid from the donor to the recipient cell, the correct answer is D. This is because the F plasmid carries genes for conjugation, allowing the recipient cell to become F+ (containing the F plasmid). The donor cell remains F. Choice A is incorrect as the outcome can be predicted based on the transfer of the F plasmid. Choice B is incorrect because the donor cell does not become F after transferring the F plasmid. Choice C is incorrect as only the recipient cell becomes F+, not both cells.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium is known for producing botulinum toxin, which causes botulism. It is an anaerobic, spore-forming bacterium commonly found in soil. Clostridium tetani causes tetanus, not botulism. Staphylococcus aureus can cause food poisoning but not botulism. Neisseria gonorrhoeae is responsible for gonorrhea, not botulism. Therefore, A is the correct answer due to the specific association of Clostridium botulinum with botulism toxin production.