Medical Microbiology Test Bank

Correct Answer: B

Rationale: The correct answer is B: Salmonellosis. The description of microorganisms resembling a tennis racket indicates the presence of Salmonella typhi, which causes salmonellosis. Salmonella bacteria can appear like tennis rackets under a microscope due to their flagella. Botulism (A) is caused by Clostridium botulinum, which does not resemble a tennis racket. Cholera (C) is caused by Vibrio cholerae, which appears as curved rods under the microscope. Dysentery (D) is usually caused by bacteria like Shigella or Entamoeba histolytica, which do not resemble tennis rackets.

Correct Answer: D

Rationale: The correct answer is D: Index of fecal coli-forms. Fecal coli-forms are bacteria found in the intestines of warm-blooded animals, including humans. Their presence in water indicates fecal contamination, which is a common source of hepatitis A transmission. Monitoring the index of fecal coli-forms can help identify potential sources of contamination and assess the risk of disease transmission. A: Number of coli-phages - Coli-phages are viruses that infect coliform bacteria and are not directly related to fecal contamination. B: Escherichia coli index - While E. coli is a type of coliform bacteria found in the intestines of warm-blooded animals, it alone may not be a reliable indicator of fecal contamination in water sources. C: Oxidability - Oxidability is a measure of the water's ability to react with oxygen and does not provide direct information about fecal contamination or the presence of pathogens like hepatitis A. In summary,

Correct Answer: A

Rationale: The correct answer is A: Icosahedral structures. Icosahedral symmetry is commonly found in viruses due to its efficient way of packing genetic material. The icosahedron has 20 equilateral triangular faces, making it ideal for viral capsids. The other choices, B: Hexahedral, C: Tetrahedral, and D: Dodecahedral structures, do not accurately describe the cubic type of symmetry seen in viruses. Hexahedral refers to a six-faced polyhedron, tetrahedral to a four-faced polyhedron, and dodecahedral to a twelve-faced polyhedron, none of which align with the structure commonly observed in viruses.

Correct Answer: A

Rationale: The correct answer is A: Tetanus. Tetanus is caused by the bacterium Clostridium tetani, which produces a neurotoxin leading to muscle stiffness, including trismus (restricted mouth opening). The patient's history of a stab wound increases the likelihood of tetanus infection due to the spores entering the body through the wound. Incorrect Choices: B: Brucellosis does not typically present with trismus and is more commonly associated with fever, joint pain, and fatigue. C: Whooping cough presents with severe coughing fits but does not cause trismus. D: Wound anaerobic infection may cause localized symptoms at the wound site but is less likely to cause trismus compared to tetanus.

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.