Correct Answer: C

Rationale: The correct answer is C: ECHO virus infection. ECHO virus is transmitted via the fecal-oral route, meaning the virus is passed from feces to the mouth. This transmission occurs through contaminated food, water, or surfaces. Relapsed fever and spotted fever are generally transmitted by arthropod vectors like ticks. Pertussis, also known as whooping cough, spreads through respiratory droplets. Therefore, the fecal-oral route is not applicable to these diseases.

Correct Answer:

Rationale: Correct Answer: C: opportunists Rationale: 1. Opportunistic microorganisms cause infections only when the host's immune system is compromised. 2. They are typically harmless in healthy individuals but can become pathogenic in weakened hosts. 3. Saprophytic microorganisms are environmental decomposers, not inherently pathogenic. 4. Facultative pathogens can cause disease in both healthy and compromised hosts. 5. Obligate pathogens always cause disease regardless of the host's condition. Summary: A: Facultative pathogens can cause disease in healthy hosts. B: Saprophytes are not inherently pathogenic. D: Obligate pathogens always cause disease.

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: 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 because virulent strains of Listeria monocytogenes exhibit multiple pathogenic factors. A: They do not have endotoxin-like substances, so this is incorrect. B: They are indeed facultative intracellular bacteria, aiding in their ability to survive and replicate inside host cells. C: They produce hemolysin, which helps them lyse red blood cells. Therefore, the correct answer is D, as all of the above statements are true for virulent strains of Listeria monocytogenes.