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Which bacteria are most commonly associated with hospital-acquired infections?
- A. Staphylococcus aureus
- B. Escherichia coli
- C. Klebsiella pneumoniae
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. Hospital-acquired infections can be caused by a variety of bacteria commonly found in healthcare settings. Staphylococcus aureus is a common cause of surgical site infections. Escherichia coli can cause urinary tract infections. Klebsiella pneumoniae is associated with pneumonia and bloodstream infections. Therefore, all three bacteria are frequently implicated in hospital-acquired infections due to their prevalence and ability to cause different types of infections in healthcare settings. Thus, the correct answer is D, as all of the listed bacteria are commonly associated with hospital-acquired infections.
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A veterenary attendant working at a cattle farm complains of joint pain, fever, indisposition and sweating at nighttime that he has been experiencing for a month. Giving the regard to such presentations and occupational history the doctor suspected brucellosis. What material taken from this patient is to be analyzed in a common microbiological laboratory?
- A. Blood serum
- B. Spinal fluid
- C. Vomit mass
- D. Urine
Correct Answer: A
Rationale: The correct answer is A: Blood serum. In suspected cases of brucellosis, blood serum is typically analyzed in a common microbiological laboratory. This is because the bacteria causing brucellosis, Brucella species, can be detected through serological tests in the blood serum. The presence of specific antibodies against Brucella in the serum confirms the diagnosis. Spinal fluid (choice B) would be analyzed in cases of suspected central nervous system infections, which are not typical for brucellosis. Vomit mass (choice C) is not a common sample for microbiological analysis in cases of brucellosis. Urine (choice D) is not the preferred sample for detecting Brucella antibodies; blood serum is the primary choice for serological testing.
Which of the following media is often used to grow Mycobacterium tuberculosis?
- A. Middlebrook’s medium
- B. Heart infusion broth
- C. MacConkey agar
- D. Middlebrook’s medium
Correct Answer: D
Rationale: The correct answer is D: Middlebrook's medium. This medium is specifically designed for the growth of Mycobacterium tuberculosis due to its low concentration of malachite green, which inhibits the growth of other bacteria but not Mycobacterium species. Middlebrook's medium also contains various nutrients that support the growth of Mycobacterium tuberculosis.
A: Middlebrook's medium is the correct answer, not incorrect.
B: Heart infusion broth is a general-purpose medium, not specific for Mycobacterium tuberculosis.
C: MacConkey agar is selective for gram-negative bacteria and would not support the growth of Mycobacterium tuberculosis.
In summary, Middlebrook's medium is the ideal choice for cultivating Mycobacterium tuberculosis due to its specific formulation that promotes the growth of this pathogen while inhibiting other bacteria.
The growth phase in which bacteria adapt to the conditions of cultivation is called:
- A. Stationary phase
- B. Log phase
- C. Lag phase
- D. Death phase
Correct Answer: C
Rationale: The correct answer is C: Lag phase. During the lag phase, bacteria adapt to the new environment before starting to grow and divide. This phase is characterized by a period of low growth as bacteria adjust their metabolism to the available nutrients. The stationary phase (A) is when growth rate equals death rate, the log phase (B) is rapid exponential growth, and the death phase (D) is when cells start to die due to nutrient depletion or accumulation of waste products. Thus, the lag phase is the initial phase where bacteria prepare for growth, making it the correct answer.
A fecal smear from a patient with severe diarrhea revealed motile Gram-negative rods with a comma shape. What is the likely causative agent?
- A. Vibrio cholerae
- B. Shigella dysenteriae
- C. Salmonella typhi
- D. Escherichia coli
Correct Answer: A
Rationale: The correct answer is A: Vibrio cholerae. This bacterium is the likely causative agent because it is known to cause severe diarrhea, and it is characterized by its motile, comma-shaped Gram-negative rods. Vibrio cholerae produces cholera toxin, leading to profuse watery diarrhea. Shigella dysenteriae causes dysentery with bloody diarrhea, Salmonella typhi causes typhoid fever, and Escherichia coli can cause various types of diarrhea but typically does not have a comma shape.
What type of immune reaction is most common in identification of vibrio cholerae
- A. Agglutination
- B. Precipitation
- C. Western blot
- D. ELISA
Correct Answer: A
Rationale: The correct answer is A: Agglutination. Agglutination is commonly used to identify Vibrio cholerae by clumping together the bacteria with specific antibodies. This reaction occurs when antibodies bind to antigens on the bacterial surface, leading to visible clumps. In contrast, Precipitation, Western blot, and ELISA are not typically used to identify Vibrio cholerae. Precipitation involves antigen-antibody complexes becoming insoluble, Western blot is used for protein detection, and ELISA is commonly used for detecting specific antigens or antibodies in a sample. Agglutination is the most appropriate choice for identifying Vibrio cholerae due to its specific interaction with the bacteria's surface antigens.