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What is the most appropriate method for diagnosis of listeriosis
- A. cultivating on artificial media and biochemical identification
- B. serological diagnosis with ELISA
- C. serological diagnosis with agglutination hype Widal
- D. cultivating in cell cultures
Correct Answer: A
Rationale: The correct answer is A: cultivating on artificial media and biochemical identification. This method is appropriate for diagnosing listeriosis because it allows for the isolation and growth of Listeria species on selective media, followed by biochemical tests to confirm the identity. Serological diagnosis with ELISA (choice B) is not as specific for Listeria and may yield false positives. Choice C, serological diagnosis with agglutination hype Widal, is not typically used for listeriosis diagnosis. Cultivating in cell cultures (choice D) is not the primary method for diagnosing listeriosis as it is less specific compared to cultivating on artificial media and biochemical identification.
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Most reliable test for detection of acute hepatitis A infection is
- A. Western blot assay for IgG anti-HAV in serum
- B. ELISA test for IgM anti-HAV in serum and HAV-Ag in stools
- C. ELISA test for IgG anti-HAV in serum
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: ELISA test for IgM anti-HAV in serum and HAV-Ag in stools. This test is the most reliable for detecting acute hepatitis A infection because IgM antibodies are produced early in the infection, indicating an active infection. Detection of HAV antigen in stools also confirms active viral shedding.
A: Western blot assay for IgG anti-HAV in serum is not the most reliable for acute infection detection as IgG antibodies are produced later in the infection and indicate past exposure or immunity.
C: ELISA test for IgG anti-HAV in serum is not the most reliable for acute infection detection as IgG antibodies are produced later in the infection and indicate past exposure or immunity.
D: None of the above is incorrect as option B is the most appropriate choice for detecting acute hepatitis A infection.
All of the following are methods for food preservation except
- A. Pasteurization
- B. Disinfection
- C. Irradiation
- D. Ultrahigh-temperature pasteurization
Correct Answer: B
Rationale: The correct answer is B: Disinfection. Disinfection is not a method for food preservation but rather a process of destroying harmful microorganisms on surfaces.
A: Pasteurization involves heating food to kill pathogens, preserving the food.
C: Irradiation uses radiation to kill bacteria and parasites, extending shelf life.
D: Ultrahigh-temperature pasteurization involves heating food at very high temperatures to extend shelf life.
In summary, disinfection is not a method used to preserve food but rather to clean surfaces.
Infections of Legionella pneumophila are treated with:
- A. Penicillins and cephalosporins
- B. Ethambutol and isoniazid
- C. Macrolides or fluoroquinolones
- D. Second and third generation cephalosporins
Correct Answer: C
Rationale: The correct answer is C: Macrolides or fluoroquinolones. Legionella pneumophila is a bacterium that causes Legionnaires' disease, a severe form of pneumonia. Macrolides (like azithromycin) and fluoroquinolones (like levofloxacin) are the recommended first-line treatments due to their ability to penetrate into lung tissues where Legionella infects. Penicillins and cephalosporins (choice A) are not effective against Legionella as it is intracellular and resistant to these antibiotics. Ethambutol and isoniazid (choice B) are used to treat tuberculosis, not Legionella infections. Second and third generation cephalosporins (choice D) are also not effective against Legionella. Therefore, the best choice for treating Legionella pneumophila infections is macrolides or fluoroquinolones.
Which one of all the clostridia that are associated with the disease myonecrosis/gas-gangrene can produce enterotoxin and could be responsible for the development of food intoxications:
- A. Clostridium septicum
- B. Clostridium perfringens
- C. Clostridium histolyticum
- D. Clostridium novyi (oedemmateins)
Correct Answer: B
Rationale: The correct answer is B: Clostridium perfringens. This bacterium is associated with myonecrosis/gas gangrene and can produce enterotoxin causing food intoxication. Clostridium septicum (A) is associated with wound infections but not known for food intoxications. Clostridium histolyticum (C) is not typically associated with myonecrosis or food intoxications. Clostridium novyi (D) is known for causing black disease in sheep and cattle, not food intoxications.
In an agar slant, bacterial colonies that appear separate or semiconfluent are referred to as:
- A. filiform
- B. echinulate
- C. beaded
- D. effuse
Correct Answer: C
Rationale: The correct answer is C: beaded. In an agar slant, beaded colonies appear as separate or semiconfluent, forming small, round colonies with gaps between them. This term accurately describes the appearance of the colonies in this context.
A: Filiform colonies are dense and opaque with smooth edges, not separate or semiconfluent.
B: Echinulate colonies have spiny projections, not the characteristic of separate or semiconfluent growth.
D: Effuse colonies spread out extensively and lack defined borders, unlike the distinct appearance of separate or semiconfluent colonies.