medical microbiology test bank

Correct Answer: A

Rationale: Saddle nose is a condition where the bridge of the nose collapses, a characteristic feature of congenital syphilis. This occurs due to inflammation and destruction of cartilage. Syphilis is caused by the bacterium Treponema pallidum. CMV, Rubella, and Toxoplasmosis do not typically cause saddle nose. CMV can result in hearing loss, Rubella can lead to cataracts and heart defects, and Toxoplasmosis may cause hydrocephalus or chorioretinitis.

Correct Answer: B

Rationale: The correct answer is Staphylococcus saprophyticus (choice B). This bacterium is a common cause of urinary tract infections in young women. It typically grows on blood agar without hemolysis and appears as Gram-positive cocci under the microscope. Proteus mirabilis (choice A) is known for urease production, causing alkaline urine. Staphylococcus aureus (choice C) is a common cause of skin and soft tissue infections, not urinary tract infections. Pseudomonas aeruginosa (choice D) is an opportunistic pathogen often seen in nosocomial infections, not typically associated with urinary tract infections in healthy individuals.

Correct Answer: B

Rationale: The correct answer is B: Sporadic disease. When an infection occurs in several persons without any epidemiological link, it is considered sporadic. This term is used to describe isolated cases that do not form a specific pattern or cluster. It indicates random occurrences and lack of connection between the affected individuals. A: Epidemic refers to a sudden increase in the number of cases of a disease within a specific population or region, usually linked by a common source or exposure. C: Endemic signifies the constant presence of a disease within a specific population or region, with cases occurring at a relatively stable rate. D: Pandemic indicates a global outbreak of a disease affecting a large number of people across multiple countries or continents.

Correct Answer: A

Rationale: The correct answer is A: Neisseria meningitidis. This bacterium is a Gram-negative diplococcus commonly associated with meningitis. The patient's symptoms of fever, headache, and neck stiffness are classic signs of meningococcal meningitis. Neisseria meningitidis is known to cause outbreaks in crowded settings. Streptococcus pneumoniae (Choice B) is a common cause of bacterial meningitis but typically appears as Gram-positive cocci. Haemophilus influenzae (Choice C) can also cause meningitis but is more commonly seen in unvaccinated children. Klebsiella pneumoniae (Choice D) is a Gram-negative bacterium but is not a typical causative agent of meningitis.

Correct Answer: C

Rationale: The correct answer is C because bacterial enzymes like amylase and protease catalyze biochemical reactions like digestion. Amylase breaks down carbohydrates, while protease breaks down proteins. This process is essential for bacterial metabolism and nutrient acquisition. Choice A (Break down toxins) is incorrect because bacterial enzymes are primarily involved in nutrient breakdown, not toxin degradation. Choice B (Facilitate movement) is incorrect as enzymes are not directly involved in bacterial movement. Choice D (Promote spore formation) is incorrect because enzymes like amylase and protease are not directly involved in spore formation.