free microbiology test bank questions pdf

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.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium is associated with food poisoning from improperly canned foods due to its ability to produce botulinum toxin, a potent neurotoxin that causes botulism. Improper canning allows spores of Clostridium botulinum to survive and germinate, producing the toxin in anaerobic conditions. The other choices are incorrect because Escherichia coli, Salmonella enterica, and Vibrio cholerae are not typically associated with food poisoning from improperly canned foods. Escherichia coli and Salmonella are more commonly linked to contaminated water or undercooked food, while Vibrio cholerae causes cholera primarily through contaminated water sources.

Correct Answer: B

Rationale: The correct answer is B: Orthomyxovirus type 1. Family Reoviridae includes Orthoreovirus types 1, 2, and 3. Orthomyxovirus belongs to a different family, Orthomyxoviridae. Therefore, B is the correct answer. Orthoreovirus types 1, 2, and 3 are part of the Reoviridae family. Choice A, C, and D are incorrect because they are all part of the Reoviridae family which includes Orthoreoviruses.

Correct Answer: A

Rationale: Rationale: 1. Unicellular organisms with two layers in cytoplasm = Entamoeba gingivalis. 2. Wide pseudopodia = characteristic of Entamoeba genus. 3. Entamoeba histolytica causes amoebic dysentery, not dental plaque. 4. Trichomonas tenax causes periodontal disease, not dental plaque. 5. Lamblia intestinalis causes giardiasis, not related to dental plaque.

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Clostridium botulinum produces botulinum toxin causing botulism. Salmonella enterica can produce enterotoxins causing food poisoning. Staphylococcus aureus also produces enterotoxins leading to food poisoning. Therefore, all three options can cause food poisoning due to their production of enterotoxins.