Free Microbiology Test Bank Questions PDF

Free Microbiology Test Bank Questions PDF Related

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A patient complains of frequent bowel movements and stool with blood admixtures ("raspberry jelly" stool). Microscopic examination revealed large mononuclear cells with absorbed red blood cells. What protozoon is this morphological structure typical for?

  • A. Entamoeba histolytica
  • B. Giardia lamblia
  • C. Campylobacter jejuni
  • D. Toxoplasma gondii
Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoon is responsible for causing amoebic dysentery, which presents with bloody diarrhea. The "raspberry jelly" appearance of stool is due to the presence of mucosal lining and blood. The large mononuclear cells with absorbed red blood cells are characteristic of the histopathology of Entamoeba histolytica infection. Giardia lamblia (B) causes watery diarrhea, not bloody stools. Campylobacter jejuni (C) is a bacterial pathogen associated with gastroenteritis, but does not typically cause bloody diarrhea. Toxoplasma gondii (D) causes toxoplasmosis, a systemic infection with symptoms such as fever and lymphadenopathy, but not bloody diarrhea.

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A 14-year-old patient was diagnosed with Hutchinson's triad: barrel-shaped incisors, parenchymatous keratitis and deafness. The revealed presentations are consistent with the following disease:

  • A. Syphilis
  • B. Toxoplasmosis
  • C. Lepra
  • D. Tuberculosis
Correct Answer: A

Rationale: The correct answer is A: Syphilis. Hutchinson's triad is a classic presentation of congenital syphilis in children. Barrel-shaped incisors, parenchymatous keratitis, and deafness are key manifestations. Barrel-shaped incisors result from mulberry molars, a type of abnormal tooth. Parenchymatous keratitis is an inflammation of the cornea, a common ocular sign in congenital syphilis. Deafness can occur due to damage to the auditory nerve caused by the infection. Choices B, C, and D are incorrect as they do not typically present with the specific triad of symptoms seen in congenital syphilis.

The term “zone of inhibition†is used in which of the following procedures?

  • A. Use-dilution test
  • B. Growth inhibition test
  • C. Disk-diffusion test
  • D. Multiple inhibition test
Correct Answer: C

Rationale: The correct answer is C: Disk-diffusion test. In the disk-diffusion test, the zone of inhibition refers to the area around an antimicrobial disk where bacterial growth is inhibited. This test is used to determine the susceptibility of bacteria to specific antibiotics. The other choices, such as A: Use-dilution test, B: Growth inhibition test, and D: Multiple inhibition test, do not specifically involve measuring the zone of inhibition and are not commonly used methods for testing antibiotic susceptibility.

Which of the following bacteria is responsible for causing gonorrhea?

  • A. Chlamydia trachomatis
  • B. Neisseria gonorrhoeae
  • C. Treponema pallidum
  • D. Escherichia coli
Correct Answer: B

Rationale: The correct answer is B: Neisseria gonorrhoeae. This bacterium is responsible for causing gonorrhea. Neisseria gonorrhoeae is a sexually transmitted bacterium that infects the mucous membranes of the reproductive tract. It is known for causing symptoms such as painful urination and discharge. Chlamydia trachomatis (choice A) is another sexually transmitted bacterium but is not responsible for gonorrhea. Treponema pallidum (choice C) causes syphilis, not gonorrhea. Escherichia coli (choice D) is a common bacterium found in the gut and is not associated with causing gonorrhea. Therefore, Neisseria gonorrhoeae is the correct answer for this question.

The class of immunoglobulins most abundant in body is:

  • A. IgG
  • B. IgE
  • C. IgD
  • D. IgM
Correct Answer: A

Rationale: The correct answer is A: IgG. IgG is the most abundant class of immunoglobulins in the body, constituting about 75% of total immunoglobulins. IgG plays a crucial role in long-term immunity, neutralizing toxins, and enhancing phagocytosis. IgE is involved in allergic reactions, IgD is mainly found on B cells and functions as a receptor, and IgM is the first antibody produced in response to an infection but is less abundant compared to IgG. Therefore, IgG is the correct choice based on its abundance and diverse functions in the immune system.

Which type of bacteria can survive in extreme salty environments?

  • A. Psychrophiles
  • B. Halophiles
  • C. Thermophiles
  • D. Mesophiles
Correct Answer: B

Rationale: The correct answer is B: Halophiles. Halophiles are bacteria that can survive in extreme salty environments. They have adapted to thrive in high salt concentrations. Psychrophiles (A) thrive in cold temperatures, Thermophiles (C) thrive in high temperatures, and Mesophiles (D) thrive in moderate temperatures. Therefore, they are not adapted to survive in extreme salty environments like Halophiles.

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