Microscopy of a smear obtained from a patient with acute purulent periostitis revealed gram-positive bacteria arranged in clusters resembling bunch of grapes. What microorganisms is this morphology typical for?

Correct Answer: A

Rationale: Rationale: Staphylococci are gram-positive bacteria that typically arrange in clusters resembling a bunch of grapes. This characteristic morphology is specific to staphylococci due to their division pattern. Sarcina, Tetracocci, and Candida fungi do not exhibit this clustering pattern. Staphylococci are commonly associated with purulent infections, making them the most likely microorganisms in this scenario.

Correct Answer: D

Rationale: The correct answer is D: Dinoflagellates. Red tides are caused by the rapid growth of certain species of dinoflagellates, which are single-celled algae. These algae produce toxins that can harm marine life and humans. Lichens (A) are not associated with red tides. While some bacteria (B) can contribute to harmful algal blooms, they are not the primary cause of red tides. Pfiesteria (C) is a type of harmful algal species, but it is not the main organism responsible for red tides. Therefore, the correct answer is dinoflagellates (D) due to their ability to cause red tides through toxin production.

Correct Answer: B

Rationale: The correct answer is B: Thayer-Martin agar. This selective media contains antibiotics that inhibit the growth of other organisms while allowing Neisseria gonorrhoeae to grow. The antibiotics in Thayer-Martin agar include vancomycin, colistin, nystatin, and trimethoprim, which target different types of bacteria, ensuring the isolation of N. gonorrhoeae. Phenylethyl alcohol agar (A) is used to isolate gram-positive organisms, not N. gonorrhoeae. MacConkey agar (C) is selective for gram-negative enteric bacteria. Mannitol salt agar (D) is used for isolating Staphylococcus species based on their ability to ferment mannitol.

Correct Answer: C

Rationale: The correct answer is C: adhesion. Adhesion refers to the attachment of microbes to surfaces in or on the body without causing harm. Infections (choice A) occur when microbes invade and multiply in the body, leading to harmful effects. Contamination (choice B) refers to the presence of unwanted or potentially harmful substances, not necessarily microbes. Disease (choice D) is a state of poor health caused by a specific agent, such as microbes, resulting in identifiable symptoms. In this context, adhesion best describes the presence of microbes without causing harm or leading to an infection.

Correct Answer: D

Rationale: The correct answer is D: Propionibacterium acnes. This bacterium plays a key role in acne formation by colonizing hair follicles, leading to inflammation and acne lesions. It produces fatty acids that contribute to the development of acne. Staphylococcus aureus (A) and Staphylococcus epidermidis (B) are not directly linked to acne. Streptococcus pyogenes (C) is associated with skin infections but not acne. In summary, Propionibacterium acnes is the primary bacterium responsible for acne due to its ability to induce inflammation and follicular blockages.