ATI RN
Mastering Microbiology Test Bank Questions
Question 1 of 5
Tuberculosis can be treated by means of combined chemotherapy that includes substances with different mechanisms of action. What antituberculous medication inhibits transcription of RNA into DNA in mycobacteria?
Correct Answer: A
Rationale: Rifampicin is the correct answer because it inhibits RNA transcription in mycobacteria by binding to the bacterial RNA polymerase. This prevents the synthesis of RNA, leading to the inhibition of protein production essential for bacterial growth. Isoniazid inhibits mycolic acid synthesis, Streptomycin inhibits protein synthesis, and Ethionamide disrupts mycolic acid synthesis. These mechanisms are different from inhibiting RNA transcription, making them incorrect choices.
Question 2 of 5
A 34 year old male patient consulted a doctor about face carbuncle. Objectively: a loose, painless edema of hypodermic tissue; black crust in the center of carbuncle, vesicular rash around it. Microbiological examination revealed static streptobacilli capable of capsule building. What microorganisms are the causative agents of this disease?
Correct Answer: B
Rationale: The correct answer is B: Staphylococcus aureus. This bacterium is a common causative agent of skin infections like carbuncles. Staphylococcus aureus is known for its ability to produce pus-filled abscesses, which aligns with the symptoms described in the question. The presence of a vesicular rash around the carbuncle further supports this diagnosis, as Staphylococcus aureus can cause skin lesions. The other choices are not correct because: A: Bacillus anthracis causes anthrax, which presents with different symptoms such as fever, malaise, and respiratory symptoms. C: Bacillus subtilis is a harmless soil bacterium commonly used in research and not known to cause skin infections. D: Bacillus anthracoides is not a known pathogen and is not associated with human infections.
Question 3 of 5
A patient has a necrotizing phlegmon of his lower extremity. A doctor suspects a gas gangrene. Microscopy reveals grampositive bacilli. In order to confirm the diagnosis further bacteriological tests should include inoculation of the material into the following nutrient medium:
Correct Answer: A
Rationale: The correct answer is A: Kitt-Tarozzi medium. This medium is specifically designed to culture Clostridium species, the causative agents of gas gangrene. Clostridium species are gram-positive bacilli that produce gas during their metabolism. Inoculating the material into Kitt-Tarozzi medium allows for the selective growth of Clostridium species, aiding in the confirmation of a gas gangrene diagnosis. Other choices are incorrect: B: Endo agar is used for the isolation of gram-negative enteric bacteria. C: Meat-peptone agar is a general-purpose medium and not specific for Clostridium species. D: Levine agar is used for the isolation of Salmonella and Shigella species, not Clostridium.
Question 4 of 5
When examining a patient presumptively diagnosed with food toxicoinfection, a doctor on duty has detected symptoms characteristic of botulism. The patient named the meals he ate the day before. What is the most probable cause of infection?
Correct Answer: A
Rationale: The correct answer is A: Homemade canned meat. Botulism is caused by the Clostridium botulinum bacteria, which thrives in low-oxygen environments like improperly canned food. Homemade canned meat poses a higher risk of contamination as it may not have been processed correctly, allowing the bacteria to grow and produce toxins. Custard pastry, sour cream, and strawberries are less likely to cause botulism as they are not typically associated with the bacteria unless improperly handled or stored. Homemade canned meat is the most probable cause based on the characteristic symptoms of botulism and the conditions that favor the growth of Clostridium botulinum in canned food.
Question 5 of 5
On the 5th day after a surgery for colon injury a patient complains of bursting pain in the postoperative wound, weakness, drowsiness, headache, fever up to 40oC. Objectively: the skin around the wound is swollen, there is gas crepitation. The wound discharges are scarce foul-smelling, of dark-gray color. What is the most likely diagnosis?
Correct Answer: A
Rationale: The correct answer is A: Anaerobic clostridial wound infection. The symptoms and signs described (bursting pain, weakness, drowsiness, fever, swollen skin, gas crepitation, foul-smelling dark-gray discharge) are classic for gas gangrene, caused by Clostridium perfringens. Gas gangrene is an anaerobic infection that thrives in devitalized tissue, such as postoperative wounds. The gas crepitation is due to gas production by the bacteria. Abscess (B) typically presents with localized swelling and fluctuance, not gas crepitation. Postoperative wound infection (C) may present with redness, warmth, and increased wound discharge but not the specific features mentioned. Erysipelas (D) is a superficial bacterial skin infection, typically caused by Streptococcus pyogenes, presenting with well-defined raised borders and redness.