microbiology chapter 14 test bank

Correct Answer: A

Rationale: The correct answer is A: Neisseria meningitidis. This bacterium is a Gram-negative diplococcus commonly associated with meningitis. Neisseria meningitidis is a leading cause of bacterial meningitis in young adults and adolescents. It is known for causing fever, headache, and neck stiffness. The other choices, Streptococcus pneumoniae, Haemophilus influenzae, and Klebsiella pneumoniae, are not typically Gram-negative diplococci and are not commonly associated with the symptoms described. Streptococcus pneumoniae is a Gram-positive coccus, Haemophilus influenzae is a Gram-negative coccobacillus, and Klebsiella pneumoniae is a Gram-negative rod. Therefore, Neisseria meningitidis is the most likely causative agent in this scenario.

Correct Answer: A

Rationale: The correct answer is A because Staphylococcus aureus can develop resistance to penicillin over time due to the production of beta-lactamase enzymes. This resistance mechanism makes it no longer susceptible to penicillin. The other choices are correct: B) S. aureus can produce beta hemolysis, C) it produces various toxins like hemolysins, leucocidins, and enterotoxins, and D) it shows a positive catalase reaction due to the presence of catalase enzyme that converts hydrogen peroxide to water and oxygen.

Correct Answer: C

Rationale: The correct answer is C because Endo, Gassner, and Levin are all examples of differential media used in microbiology. These media contain specific components that allow for the differentiation of different types of microorganisms based on their metabolic characteristics or biochemical reactions. Lowenstein-Jensen and Petraniani (choice A) are selective media for mycobacteria, not differential. Apoholate-citrate agar and Brilliant-green phenol-red Lactose agar (choice B) are selective media for Salmonella and E. coli, respectively, not differential. Therefore, the correct choice is C as it includes examples of differential media commonly used for microbial identification.

Correct Answer: C

Rationale: The correct answer is C. Bacterial spores are NOT used for cell division. Bacterial spores are dormant, resistant forms of bacteria that are formed in response to harsh environmental conditions. They are not involved in cell division but rather serve as a survival mechanism for the bacteria. A: They can deform the cell or not - This is true. Bacterial spores can deform the cell or not depending on the conditions. B: They can be terminal, subterminal, and central - This is true. Bacterial spores can be located at different positions within the bacterial cell. D: They are formed for 6-8h - This is incorrect. The formation of bacterial spores can take variable time periods depending on the species and environmental conditions.

Correct Answer: A

Rationale: The correct answer is A: Clostridia. Fusiform spore-forming microorganisms that stain violet-blue with Gram's stain are characteristic of Clostridia. Clostridia are anaerobic, rod-shaped bacteria known for their ability to form spores and cause diseases such as tetanus and botulism. Summary of other choices: B: Streptococci are spherical, not fusiform, and typically do not form spores. C: Spirochaete are spiral-shaped bacteria and do not typically form spores. D: Actinomycete are filamentous bacteria that do not typically form spores and do not stain violet-blue with Gram's stain.