free microbiology test bank questions pdf

Correct Answer: C

Rationale: The correct answer is C: Thermophiles. Thermophiles are bacteria that thrive in high temperatures, typically between 45-80 degrees Celsius. They have adapted to extreme heat environments and have enzymes that function optimally at high temperatures. Mesophiles (A) grow best at moderate temperatures, Psychrophiles (B) thrive in cold temperatures, and Halophiles (D) thrive in high salt concentrations. Therefore, only Thermophiles are specifically adapted to high temperatures, making it the correct choice.

Correct Answer: A

Rationale: The correct answer is A: Leptospira. Leptospira is a spiral-shaped bacterium that causes a disease known as leptospirosis, characterized by fever, jajsondice, hemorrhagic rash, and renal insufficiency. The characteristic spiral shape of the bacteria, resembling 'C' and 'S' letters, is a key identifying feature. Leptospira is commonly associated with contaminated water sources and can be transmitted to humans through contact with infected animals or water. Summary of other choices: B: Treponema - Treponema pallidum is the causative agent of syphilis, which does not typically present with the combination of symptoms described in the question. C: Borrelia - Borrelia species are associated with Lyme disease and relapsing fever, but do not match the specific symptoms and histological appearance described in the question. D: Spirochaeta - Spirochaeta is a genus of bacteria, but specific species within

Correct Answer: A

Rationale: The correct answer is A: Homemade canned meat. Botulism is often caused by consuming improperly canned or preserved foods, particularly meats. The spores of the Clostridium botulinum bacteria can grow in anaerobic conditions, such as those found in improperly canned foods, leading to the production of the botulinum toxin. The symptoms of botulism align with those characteristic of the patient's condition. Explanation of why the other choices are incorrect: B: Custard pastry from private bakery - Unlikely to be the cause of botulism as this type of food is not typically associated with the growth of Clostridium botulinum. C: Sour cream from local dairy factory - While dairy products can sometimes be sources of foodborne illness, botulism is not commonly associated with sour cream. D: Strawberries from suburban vegetable garden - Botulism is not typically transmitted through fresh fruits or vegetables, making this an unlikely source of infection.

Correct Answer: B

Rationale: The correct answer is B: Mycobacterium tuberculosis. Mycobacterium tuberculosis is the causative agent of tuberculosis, as it specifically infects the lungs and can spread to other parts of the body. Mycobacterium leprae (Choice A) causes leprosy, not tuberculosis. Bacillus anthracis (Choice C) causes anthrax, not tuberculosis. Staphylococcus aureus (Choice D) is a common bacterium known for causing skin infections, not tuberculosis. Therefore, Mycobacterium tuberculosis is the correct answer for the causative agent of tuberculosis.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. 1. Gram-positive cocci in chains suggest streptococci. 2. Catalase-negative indicates it's not staphylococci. 3. Beta-hemolytic points towards Group A Streptococcus (S. pyogenes). Summary: B. Streptococcus pneumoniae is not beta-hemolytic. C. Enterococcus faecalis is not typically chains. D. Staphylococcus aureus is catalase-positive.