microbiology chapter 12 test bank

Correct Answer: B

Rationale: The correct answer is B: biofilms. Biofilms are structured communities of microorganisms that adhere to a surface and are embedded in a matrix. This is the most appropriate term as it specifically describes the organization of various species into complex communities on a surface. Colonies (A) refer to groups of cells of the same species, not necessarily multiple species. Ecosystems (C) are broader systems involving interactions between living organisms and their environment. Plagues (D) are outbreaks of disease, not a term used to describe organized microbial communities.

Correct Answer: C

Rationale: The correct answer is C: It is non-motile and non-spore forming. Pseudomonas aeruginosa is motile due to its flagella and is non-spore forming. A is correct because it is a Gram-negative bacterium, and B is correct as it is oxidase-positive. D is incorrect because C is not true.

Correct Answer: C

Rationale: The correct answer is C. Negri bodies are not associated with measles but with rabies. Step 1: Measles is a childhood infection with a rash (A). Step 2: Koplik spots are small white spots on a red base found inside the mouth and are characteristic of measles (B). Step 3: Negri bodies are eosinophilic cytoplasmic inclusions found in neurons infected with rabies virus, not measles (C). Step 4: Prophylaxis for measles is through the MMR vaccine, which is a live attenuated vaccine (D). Therefore, choice C is incorrect as it does not pertain to measles.

Correct Answer: A

Rationale: Step 1: Trichomonal gingivostomatitis is caused by the parasite Trichomonas tenax. Step 2: Metronidazole is the drug of choice for treating infections caused by anaerobic organisms like Trichomonas. Step 3: Metronidazole effectively targets and eliminates Trichomonas parasites in the oral cavity. Step 4: Therefore, the correct drug choice for treating trichomonal gingivostomatitis is Metronidazole. Summary: - Ampicillin (B) is an antibiotic effective against Gram-positive bacteria, not parasites. - Gentamicin sulfate (C) is an antibiotic used for bacterial infections, not parasitic infections. - Nystatin (D) is an antifungal medication used for treating fungal infections, not parasitic infections like trichomonal gingivostomatitis.

Correct Answer: A

Rationale: The correct answer is A (20 min) because Escherichia coli typically has a generation time of around 20 minutes, meaning the time it takes for a bacterial population to double. This rapid reproduction rate is a key characteristic of E. coli. Option B (60 min) is incorrect as it is longer than the usual generation time. Option C (20 hours) is too long for E. coli's generation time. Option D (24 hours) is also incorrect as it is much longer than the typical generation time of E. coli.