Which of the following is a characteristic of Gram-positive bacteria?

Correct Answer: C

Rationale: The correct answer is C: Thick peptidoglycan layer. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain in the Gram staining process, leading to a purple color. This thick layer is a defining characteristic of Gram-positive bacteria. Rationale: A: Thin peptidoglycan layer is incorrect because Gram-positive bacteria have a thick peptidoglycan layer. B: Presence of an outer membrane is incorrect because Gram-positive bacteria lack an outer membrane. D: Presence of lipopolysaccharides is incorrect because lipopolysaccharides are typically found in the outer membrane of Gram-negative bacteria, not Gram-positive bacteria.

Correct Answer: A

Rationale: The correct answer is A: Francisella tularensis. This bacterium is classified as a class A bioterrorism agent due to its high virulence and potential for mass casualties. It can cause tularemia, a severe and potentially fatal disease. The other choices, Hepatitis B, E. coli, and Bacillus subtilis, are not considered class A bioterrorism agents. Hepatitis B is a virus causing liver inflammation, E. coli is a common bacterium found in the gut, and Bacillus subtilis is a beneficial bacterium used in various industries. Therefore, Francisella tularensis is the correct choice based on its high pathogenicity and bioterrorism potential.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. The presence of Gram-positive rods with terminal spores resembling drumsticks indicates Clostridium tetani, the causative agent of tetanus. This bacterium forms spores at one end, giving it a drumstick appearance under the microscope. Clostridium perfringens (B) and Clostridium botulinum (D) do not have terminal spores. Bacillus anthracis (C) forms spores but typically appears as a square-ended or bamboo stick shape. Therefore, based on the microscopy findings, Clostridium tetani is the most likely microorganism responsible for the wound infection.

Correct Answer: C

Rationale: Step-by-step rationale for why choice C (Adenoviridae) is correct: 1. Adenoviruses commonly cause respiratory illnesses such as the common cold and bronchitis. 2. They are highly contagious and easily spread through respiratory secretions. 3. Adenoviruses are a common cause of viral conjunctivitis as well. 4. Other choices are incorrect because herpesviruses (choice A) typically cause different types of infections, papovaviruses (choice B) are not common respiratory pathogens, and poxviruses (choice D) are not typically associated with respiratory illnesses.

Correct Answer: A

Rationale: The correct answer is A: aspergillosis and candidiasis. Detection of galactomannan and free mannan is commonly used in diagnosing these fungal infections. Galactomannan is a component of the cell wall of Aspergillus species, while free mannan is associated with Candida species. This detection method helps in identifying these specific fungal infections accurately. B: Syphilis is caused by a bacterium, Treponema pallidum, and is not diagnosed using galactomannan or free mannan detection. C: Leptospirosis is a bacterial infection caused by the Leptospira species and is not diagnosed using galactomannan or free mannan detection. D: HIV infection is a viral infection caused by the human immunodeficiency virus and is not diagnosed using galactomannan or free mannan detection.

Correct Answer: C

Rationale: The correct answer is C. Prostatitis is inflammation of the prostate gland, leading to symptoms like painful urination, fever/chills, and weak urine flow. Painful urination is due to irritation of the urinary tract by the inflamed prostate. Fever/chills indicate an infection, common in prostatitis. Weak urine flow is due to obstruction caused by the inflamed prostate. Choice A is incorrect as muscle aches, sore throat, and swollen lymph nodes are not typical symptoms of prostatitis. Choice B is incorrect as painful joints and nausea are not characteristic symptoms. Choice D is almost identical to the correct answer but includes an extra symptom of painful joints, which is not associated with prostatitis.

Correct Answer: C

Rationale: Rationale: 1. Candida is a fungus commonly isolated from clinical specimens. 2. Sabouraud agar is the most suitable medium for Candida due to its low pH and high dextrose content. 3. Low pH inhibits bacterial growth, while dextrose promotes fungal growth. 4. Zeisler media, Chocolate agar, and Muller-Hinton agar are not specific for fungal isolation. Summary: - Zeisler media is used for anaerobic bacteria. - Chocolate agar is used for fastidious organisms like Haemophilus. - Muller-Hinton agar is for antibiotic susceptibility testing, not fungal isolation.

Correct Answer: B

Rationale: The correct answer is B: Cholera. Cholera is caused by Gram-negative curved rod-like bacteria called Vibrio cholerae, commonly found in contaminated water or food. The characteristic symptom of cholera is profuse watery diarrhea, which matches the patient's presentation. Typhoid fever (A) is caused by Salmonella typhi, which is not a curved rod-like bacteria. Diphtheria (C) is caused by Corynebacterium diphtheriae, a Gram-positive bacterium, and does not typically cause diarrhea. Intestinal form of plague (D) is caused by Yersinia pestis, which is not a curved rod-like bacteria and does not typically present with diarrhea.

Correct Answer: D

Rationale: The correct answer is D: commensalism. In commensalism, one organism benefits while the other is neither helped nor harmed. In this relationship, the waste product of one organism serves as a nutrient source for another without affecting the first organism. Mutualism (A) involves both organisms benefiting, competition (B) involves a struggle for resources, and synergism (C) involves cooperative interactions. Commensalism is the only choice where one organism benefits from the waste product of another without any impact on the producer.