microbiology an introduction test bank

Correct Answer: D

Rationale: The correct answer is D: Proteus vulgaris. This is because Proteus species are non-lactose-fermenting, Gram-negative rods that produce gas in nutrient broth. They are known to cause severe abdominal pain due to their ability to invade the intestinal mucosa. A: Salmonella enterica is a lactose-fermenting organism and typically does not produce gas in nutrient broth. B: Shigella dysenteriae is a lactose-negative organism but does not produce gas in nutrient broth. C: Escherichia coli is a lactose-fermenting organism and does not typically produce gas in nutrient broth. In summary, the presence of non-lactose-fermenting, gas-producing Gram-negative rods points towards Proteus vulgaris as the most likely causative agent of the severe abdominal pain.

Correct Answer: B

Rationale: The correct answer is B because live vaccines can potentially revert to a virulent form, although this is extremely rare. This is due to the live attenuated virus in the vaccine potentially mutating back to a more dangerous form. Live vaccines are designed to be weakened but there is a small risk of reversion. Therefore, statement B is not correct. A: This statement is correct as immunocompromised individuals may have adverse reactions to live vaccines due to their weakened immune system. C: This statement is correct as microbes with many serotypes can make it challenging to develop a vaccine that covers all variations. D: This statement is correct as side effects to vaccination, although usually mild and temporary, can occur in some individuals.

Correct Answer: C

Rationale: Rationale: Metronidazole is the drug of choice for systemic amebiasis due to its high efficacy against Entamoeba histolytica. It has good tissue penetration and can treat intestinal, liver, and lung involvement. Quiniofone (A) has limited use and is not recommended for amebiasis. Enteroseptol (B) is not effective against systemic amebiasis. Tetracycline (D) is not the first-line treatment for amebiasis and has limited efficacy against Entamoeba histolytica.

Correct Answer: B

Rationale: The correct answer is B because reinfection is indeed possible with rabies virus. Step 1: Reinfection occurs if a person is exposed to the virus again after initial infection. Step 2: Once infected, the virus can remain dormant in the body and become active upon re-exposure. Step 3: Therefore, it is essential to continue preventive measures even after initial immunization. Summary: Choices A, C, and D are incorrect because antibodies develop within 14-15 days post-immunization, HRIG is administered shortly after exposure, and a specific vaccination schedule is followed for rabies prophylaxis, respectively.

Correct Answer: D

Rationale: The correct answer is D. Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa all produce endotoxins that can lead to septic shock. Endotoxins are part of the outer membrane of Gram-negative bacteria and can trigger a systemic inflammatory response if released into the bloodstream. E. coli and Salmonella are common causes of bacterial infections that can lead to septic shock, while P. aeruginosa is a known opportunistic pathogen that can produce endotoxins. Therefore, all three bacteria can cause septic shock by releasing endotoxins. Choices A, B, and C are incorrect because each of these bacteria individually can produce endotoxins that contribute to the development of septic shock.