Mastering Microbiology Test Bank

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A 34-year-old male visited Tajikistan. After return, he complains of fever up to 40oC which occurs every second day and is accompanied by chills, sweating. Hepatosplenomegaly is present. Blood test results: RBC- 3x1012/l, b- 80 g/l, WBC- 4x109/l, eosinophils - 1%, stab neutrophils - 5%, segmented neutrophils - 60%, lymphocytes - 24%, monocytes - 10%, ESR - 25 mm/h. What is the provisional diagnosis?

  • A. Malaria
  • B. Infectious mononucleosis
  • C. Sepsis
  • D. Typhoid fever
Correct Answer: A

Rationale: The correct answer is A: Malaria. The patient's travel history to an endemic area like Tajikistan, along with symptoms of fever with chills, sweating, and hepatosplenomegaly, are classic for malaria. The blood test results show anemia (low RBC and hemoglobin levels), which can occur in malaria due to hemolysis. The presence of eosinophils and lymphocytes are not typical for malaria, but the overall clinical picture fits. Infectious mononucleosis (choice B) typically presents with sore throat, lymphadenopathy, and atypical lymphocytosis, which are not seen in this case. Sepsis (choice C) is characterized by systemic inflammatory response syndrome and organ dysfunction due to infection, which does not align with the symptoms and findings in the case. Typhoid fever (choice D) usually presents with gradual onset of sustained fever, abdominal pain, headache, and constipation, which are not present in this patient

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Which of the following is not a bacterial antibiotic resistance mechanism

  • A. Reduced permeability
  • B. Cell-wall regrowth
  • C. Over-expression of target
  • D. c) Efflux pump
Correct Answer: B

Rationale: The correct answer is B: Cell-wall regrowth. This is not a bacterial antibiotic resistance mechanism because antibiotics target specific components in bacteria, such as cell wall synthesis, making regrowth impossible in the presence of antibiotics. Reduced permeability (A) decreases antibiotic entry, Over-expression of target (C) reduces antibiotic effectiveness, and Efflux pump (D) actively removes antibiotics from the cell, all contributing to antibiotic resistance. In summary, cell-wall regrowth is not a mechanism of antibiotic resistance, unlike the other choices that actively promote bacterial survival against antibiotics.

The main function of bacterial ribosomes is:

  • A. DNA replication
  • B. protein synthesis
  • C. cell wall synthesis
  • D. RNA splicing
Correct Answer: B

Rationale: The correct answer is B: protein synthesis. Bacterial ribosomes are responsible for translating messenger RNA into proteins through a process called translation. Ribosomes are composed of both protein and RNA molecules and facilitate the binding of transfer RNA to the messenger RNA to assemble the amino acids in the correct order to form a protein. DNA replication (A) is carried out by enzymes such as DNA polymerase, not ribosomes. Cell wall synthesis (C) is a process involving enzymes that build the structure of the cell wall in bacteria. RNA splicing (D) is a eukaryotic process that involves removing introns from pre-mRNA molecules, which is not a function of bacterial ribosomes.

While examining the feces of a patient with diarrhea, cysts with four nuclei were found. What protozoan is most likely causing the condition?

  • A. Entamoeba histolytica
  • B. Lamblia
  • C. Trichomonas
  • D. Balantidium
Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoan causes amoebiasis, which presents with symptoms like diarrhea. The cysts with four nuclei found in the feces are characteristic of Entamoeba histolytica. This protozoan is known to cause invasive infection, leading to tissue destruction and ulcers in the intestines. Lamblia (choice B) typically presents with cysts containing two nuclei. Trichomonas (choice C) is a sexually transmitted parasite and does not form cysts. Balantidium (choice D) is a ciliated protozoan that does not have four nuclei in its cyst form.

Rod-shaped bacteria, some of which are endospore forming, are referred to as:

  • A. cocci
  • B. bacilli
  • C. spirals
  • D. vibrios
Correct Answer: B

Rationale: The correct answer is B. Bacilli are rod-shaped bacteria, some of which are endospore forming. Cocci are spherical, spirals are spiral-shaped, and vibrios are curved rod-shaped bacteria. Bacilli specifically refer to rod-shaped bacteria, making it the correct answer in this context.

Which bacterial structure helps in the movement towards or away from chemical stimuli?

  • A. Flagella
  • B. Pili
  • C. Capsule
  • D. Fimbriae
Correct Answer: A

Rationale: Flagella are the correct answer because they are long, whip-like structures that aid in bacterial movement towards or away from chemical stimuli. They rotate like propellers, allowing the bacterium to navigate its environment. Pili are used for attachment, not movement. Capsules are involved in protection and adherence, not chemotaxis. Fimbriae help in attachment to surfaces, not in movement towards stimuli.

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