The territory of an old burial ground for animal refuse that hasn't been used for over 50 years is meant for house building. But soil investigation showed the presence of viable spores of a causative agent causing a very dangerous disease. What microorganism might have been preserved in soil for such a long period of time?

Correct Answer: A

Rationale: The correct answer is A: Bacillus anthracis. This bacterium is known to form highly resistant spores that can survive for long periods in soil. Bacillus anthracis causes anthrax, a dangerous disease that can be transmitted to humans and animals. The other choices, Francisella tularensis, Brucella abortus, and Yersinia pestis, do not form spores as resistant as Bacillus anthracis. Therefore, only Bacillus anthracis is likely to have survived in the soil of the old burial ground for animal refuse for over 50 years.

Correct Answer: A

Rationale: The correct answer is A: Air. In transmissive infections, the vector refers to the means by which the infectious agent is transmitted from one host to another. Air can carry pathogens such as viruses and bacteria, leading to respiratory infections like the flu or tuberculosis. Airborne transmission occurs when droplets containing the pathogens are inhaled. Objects (B), medical devices (C), and water (D) can also transmit infections, but they are not specifically related to transmissive infections. Objects and medical devices can harbor pathogens, while waterborne infections are transmitted through contaminated water sources. However, in the context of transmissive infections, the primary vector is the air due to its ability to carry infectious agents over distances.

Correct Answer: C

Rationale: The correct answer is C: Helicobacter pylori. Group I organisms are classified based on their low infectious doses and potential for bioterrorism. H. pylori is known to cause gastric ulcers and is categorized as a Group I organism due to its ability to cause disease at low doses. A: Francisella tularensis is a Group A bioterrorism agent, not Group I. B: Clostridium difficile is not typically classified as a Group I organism. D: Bacillus anthracis is a Group A bioterrorism agent, not Group I.

Correct Answer: B

Rationale: The correct answer is B: Protection against phagocytosis. The bacterial capsule is a protective layer outside the cell wall that helps bacteria evade phagocytosis by the host immune system. It acts as a physical barrier against immune cells like macrophages and neutrophils, allowing the bacteria to survive and multiply in the host. Energy production (A), DNA replication (C), and protein synthesis (D) are essential cellular functions but are not directly associated with the major function of the bacterial capsule, which is protection against phagocytosis.

Correct Answer: A

Rationale: The correct answer is A: 4 and 250. Coli index is calculated by dividing the number of red colonies by the volume of water analyzed, which gives 2 red colonies / 500 ml = 4. Coli titer is the reciprocal of the coli index, so it is 1 / 4 = 250. This indicates the concentration of coliform bacteria in the water sample. Choices B, C, and D are incorrect as they do not follow the correct calculation steps for determining the coli index and coli titer. B has the correct coli index but incorrect coli titer. C and D have the values reversed, leading to incorrect results.

Correct Answer: A

Rationale: Rationale: A: Incorrect - The complement system is not directly involved in the viral neutralization reaction. B: Correct - Specific antibodies neutralize viruses by blocking their ability to infect cells. C: Incorrect - Antibodies are titrated, but only one serum sample is required for neutralization testing. D: Incorrect - Viral neutralization is primarily used to measure antibody response, not to identify newly isolated viruses.

Correct Answer: D

Rationale: Correct Answer: D (Clostridium difficile) Rationale: 1. Clostridium difficile is primarily associated with gastrointestinal infections, particularly antibiotic-associated colitis. 2. Staphylococcus aureus, Clostridium perfringens, and Pseudomonas aeruginosa are commonly associated with skin infections. 3. Staphylococcus aureus can cause impetigo, boils, and cellulitis. 4. Clostridium perfringens can cause gas gangrene. 5. Pseudomonas aeruginosa can cause hot tub folliculitis and swimmer's ear.

Correct Answer: B

Rationale: The correct answer is B: caliciviruses. Caliciviruses are known to be (+) ssRNA viruses that cause gastroenteritis in a wide range of animals, including birds, cats, dogs, pigs, sheep, cows, and humans. These viruses are highly contagious and can spread through contaminated food or water. Rotaviruses (A) are also a common cause of gastroenteritis, but they are not exclusively isolated from the mentioned animals. Adenoviruses (C) typically cause respiratory or eye infections, not gastroenteritis. Noroviruses (D) are also a major cause of gastroenteritis in humans, but they are not commonly found in animals other than humans.

Correct Answer: A

Rationale: The correct method of laboratory diagnostics for suspected malaria is blood examination. Malaria is diagnosed by detecting the presence of the Plasmodium parasite in the patient's blood. This can be done through microscopy to identify the parasite in a blood smear or through rapid diagnostic tests (RDTs) that detect specific antigens produced by the parasite. Blood examination allows for the direct visualization of the parasite, making it the most accurate method for diagnosing malaria. Immunological tests, stool examination, and urine examination are not suitable for diagnosing malaria as the parasite primarily resides in the red blood cells. Stool and urine examinations are more commonly used for diagnosing gastrointestinal or urinary tract infections, respectively.