Bacteriological inspection of disinfection quality at a pharmacy revealed a microorganism in an utility room (in the sink). The microorganism has the following properties: mobile nonspore-forming gram- negative bacteria that form capsular substance, grow well on ordinary nutrient media, secrete the blue-green pigment. This microorganism is most likely to be of the following genus:

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas. Rationale: 1. Mobile nonspore-forming gram-negative bacteria with a capsule substance indicate Pseudomonas. 2. Pseudomonas grow well on ordinary nutrient media, matching the description. 3. The secretion of a blue-green pigment is a characteristic feature of Pseudomonas. 4. Proteus is a gram-negative bacterium but does not match all the given properties. 5. Clostridium is a gram-positive bacterium that forms spores. 6. Shigella is a gram-negative bacterium but does not have the other characteristics mentioned. Therefore, based on the properties described, the most likely genus of the microorganism is Pseudomonas.

Correct Answer: A

Rationale: The correct answer is A because a soft chancre is a type of sexually transmitted infection caused by the bacterium Haemophilus ducreyi. It presents as a painless ulcer on the genitals. The other choices are incorrect. B is incorrect because STIs can enter the body through various routes, not only the urogenital tract mucosa. C is incorrect because immunity to syphilis is not lifelong; reinfection is possible. D is incorrect because STIs can occur in any country regardless of social status or hygiene levels.

Correct Answer: D

Rationale: The correct answer is D: chemoheterotrophs. Chemoheterotrophs use organic compounds as both their carbon source and energy source. They obtain energy by breaking down organic molecules through cellular respiration. Photoautotrophs (A) use light energy to produce organic compounds, chemoautotrophs (B) use inorganic compounds for energy, and photoheterotrophs (C) use light energy but require organic compounds as a carbon source. Therefore, chemoheterotrophs best describe bacteria that obtain both carbon and energy from organic compounds.

Correct Answer: A

Rationale: The correct answer is A: McConkey agar. Selective media selectively inhibit the growth of certain organisms while allowing others to grow. McConkey agar contains crystal violet and bile salts that inhibit the growth of Gram-positive bacteria, making it selective for Gram-negative bacteria. Choices B and C are not selective media, as they do not specifically inhibit the growth of certain types of bacteria. Choice D is incorrect as McConkey agar is indeed an example of selective media.

Correct Answer: A

Rationale: The correct answer is A: 96% ethanol. In Gram's staining method, after applying gentian violet, Lugol's solution, and aqueous fuchsin, the next step is to use a decolorizing agent like 96% ethanol to wash away the excess stain from the Gram-negative bacteria. This step is crucial as it helps differentiate between Gram-positive and Gram-negative bacteria based on their cell wall properties. The other choices are incorrect because sulfuric acid is not used in Gram's staining method, methylene blue is typically used in other staining techniques like the simple stain, and carbolic fuchsin is not a standard reagent in the Gram's staining process.

Correct Answer: C

Rationale: The correct answer is C: Salmonella typhi. Typhoid fever is caused by the bacterium Salmonella typhi, specifically transmitted through contaminated food and water. Shigella dysenteriae causes bacillary dysentery, Vibrio cholerae causes cholera, and Escherichia coli can cause various gastrointestinal illnesses, but not typhoid fever. Identifying the causative agent is crucial for effective treatment and prevention strategies.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba gingivalis. Firstly, it is important to note that Entamoeba gingivalis is commonly found in the oral cavity, specifically in carious cavities. Secondly, Entamoeba gingivalis belongs to the Sarcodina class, which is characterized by their amoeboid movement using pseudopods. This protozoa is associated with oral health issues, particularly in individuals with poor oral hygiene. Now, let's analyze why the other choices are incorrect: B: Entamoeba histolutica is known for causing amoebic dysentery, not commonly associated with oral cavities. C: Entamoeba coli is typically found in the human large intestine, not in oral cavities. D: Amoeba proteus is a free-living amoeba commonly used in laboratory studies and not typically associated with oral cavity infections.

Correct Answer: B

Rationale: The correct answer is B: Thick gram-positive non-sporeforming bacilli. In botulism, the causative agent, Clostridium botulinum, is a thick gram-positive bacilli that does not form spores. This is a key characteristic morphologic feature. A: Gram-positive spore-forming bacilli with subterminal spore - This is incorrect as Clostridium botulinum does not have subterminal spores. C: Gram-positive spore-forming bacilli with terminal spore - Incorrect because Clostridium botulinum does not form spores. D: Thin mobile spore-forming bacilli with central spore - Incorrect because Clostridium botulinum is not thin, mobile, or spore-forming. In summary, the most characteristic morphologic feature of the botulism agent is being thick, gram-positive, and non-sporeforming, making choice B the correct answer.

Correct Answer: B

Rationale: The correct answer is B: prophage. In the repressed stage, a phage integrates its DNA into the host cell's chromosome, becoming a prophage. This integration allows the phage to replicate along with the host cell without causing immediate lysis. A: Antiphage is not a term used to describe a phage in a repressed stage. C: Virulent phage refers to a phage that immediately causes lysis of the host cell. D: Latent phage is not a commonly used term in this context.