Dengue virus is member of a family called

Correct Answer: C

Rationale: The correct answer is C: Flaviviridae. Dengue virus belongs to the Flaviviridae family because it is a flavivirus. Flaviviruses are a group of RNA viruses known to cause diseases in humans, such as dengue fever, Zika virus, and yellow fever. This family is characterized by its single-stranded, positive-sense RNA genome and enveloped virion structure. Hepadnaviridae (choice A), Parvoviridae (choice B), and Picornaviridae (choice D) are all different families of viruses that do not include the dengue virus. Hepadnaviridae includes hepatitis B virus, Parvoviridae includes parvoviruses, and Picornaviridae includes enteroviruses like poliovirus.

Correct Answer: B

Rationale: The growth of bacteria is a result of water adsorption because water is essential for various metabolic processes within the bacterial cells, such as nutrient uptake, energy production, and waste removal. Water serves as a medium for chemical reactions to occur and provides structural support to the bacteria. Without sufficient water, bacteria cannot thrive and reproduce. A: Air consumption is incorrect because while bacteria may require oxygen for respiration, it is not the primary factor for their growth. C: Enzyme production is incorrect because enzymes are important for various cellular functions but do not directly influence bacterial growth. D: Radio isotopes are incorrect as they are not essential for bacterial growth and can even be harmful to bacterial cells.

Correct Answer: B

Rationale: The capsule of Bacillus anthracis is made of polypeptide. This is because the capsule is composed of a protein-based material that surrounds the bacterium, providing protection and aiding in its virulence. Polysaccharides, lipids, and the absence of capsules are not characteristic of Bacillus anthracis' capsule structure, making choices A, C, and D incorrect, respectively.

Correct Answer: B

Rationale: The correct answer is B: non-spore forming encapsulated gram-negative bacterium. Francisella tularensis is a non-spore forming bacterium, which rules out choices A and D. It is encapsulated, which eliminates choice C. The encapsulation of the bacterium helps it evade the host immune system, leading to its pathogenicity. This encapsulated bacterium is responsible for causing the zoonotic disease tularemia in humans.

Correct Answer: B

Rationale: The correct answer is B: Yersinia pestis. Yersinia pestis is the bacterium responsible for causing the plague, specifically the bubonic plague. It is transmitted through fleas and rodents. Escherichia coli (A) is a common gut bacterium, Clostridium difficile (C) causes antibiotic-associated diarrhea, and Staphylococcus aureus (D) is associated with skin infections, but they are not responsible for causing the plague.

Correct Answer: A

Rationale: The correct answer is A because Gram-negative bacteria have a unique cell envelope structure consisting of a cytoplasmic membrane, a peptidoglycan layer, and an outer membrane. The cytoplasmic membrane is the innermost layer that separates the cytoplasm from the external environment. The peptidoglycan layer provides structural support to the cell. The outer membrane acts as an additional protective barrier and contains lipopolysaccharides. Choice B is incorrect because Gram-negative bacteria have an outer membrane in addition to the cytoplasmic membrane and peptidoglycan layer. Choice C is incorrect because Gram-negative bacteria have more than just a peptidoglycan layer in their cell envelope. Choice D is incorrect as the cell envelope of Gram-negative bacteria does have specific components.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. The description of Gram-positive cocci in pairs with pointed ends and capsules matches the morphology of S. pneumoniae. This bacterium is known to cause pneumonia, especially in individuals with underlying conditions like COPD. Staphylococcus aureus (B) typically appears in clusters, not pairs. Klebsiella pneumoniae (C) is a Gram-negative rod, not a cocci. Neisseria meningitidis (D) is a Gram-negative diplococcus, not a cocci. Hence, based on the morphology and clinical context, Streptococcus pneumoniae is the likely microorganism causing pneumonia in this patient.

Correct Answer: A

Rationale: The correct answer is A: Neisseria meningitidis. This is because Neisseria meningitidis is a Gram-negative diplococcus known to cause bacterial meningitis, presenting with fever, headache, and neck stiffness. It is a common cause of meningitis in young adults and teenagers. Streptococcus pneumoniae (B) is a Gram-positive bacteria and a common cause of bacterial pneumonia, not meningitis. Haemophilus influenzae (C) is a Gram-negative coccobacillus that can cause meningitis, but it is less common in adults. Klebsiella pneumoniae (D) is a Gram-negative bacillus known to cause pneumonia and urinary tract infections, not meningitis.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. 1. Gram-positive cocci in chains: characteristic of Streptococcus species. 2. Catalase-negative: Streptococcus species are catalase-negative. 3. Beta-hemolytic: S. pyogenes is beta-hemolytic on blood agar. Therefore, S. pyogenes fits all these criteria. B: Streptococcus pneumoniae is catalase-negative but alpha-hemolytic, not beta-hemolytic. C: Enterococcus faecalis is catalase-negative, but not typically beta-hemolytic or in chains. D: Staphylococcus aureus is catalase-positive and not in chains.