A patient with severe abdominal pain and diarrhea had a stool sample cultured. The bacteria were Gram-negative rods that did not ferment lactose. What is the most likely causative agent?

Correct Answer: A

Rationale: The correct answer is A: Salmonella enterica. This is because Salmonella are Gram-negative rods that do not ferment lactose, which fits the description in the question. Additionally, Salmonella is a common cause of severe abdominal pain and diarrhea. Shigella dysenteriae is a Gram-negative rod that also causes severe diarrhea but it does not share the characteristic of not fermenting lactose. Escherichia coli is a Gram-negative rod that does ferment lactose. Proteus vulgaris is also a Gram-negative rod but it is not commonly associated with severe abdominal pain and diarrhea, making it an unlikely causative agent in this scenario.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Mycobacterium leprae is the correct answer as it is the bacteria known to cause leprosy. 2. Clostridium perfringens is incorrect as it is associated with gas gangrene. 3. Streptococcus pneumoniae is incorrect as it is commonly linked to pneumonia and meningitis. 4. Neisseria gonorrhoeae is incorrect as it causes gonorrhea, a sexually transmitted infection. In summary, Mycobacterium leprae is the only bacteria among the choices specifically known to cause leprosy, making it the correct answer.

Correct Answer: D

Rationale: Rationale: - A: The mycelium is indeed made up of intertwined hyphae, which are the branching filaments of fungi. - B: Part of the mycelium does grow into the medium to acquire nutrients, forming the substrate mycelium. - C: Some parts of the mycelium remain above the medium to aid in reproduction and spore dispersal, forming the aerial mycelium. Therefore, all statements (A, B, and C) are correct, making choice D the correct answer. The mycelium exhibits both intertwined hyphae, substrate mycelium, and aerial mycelium to facilitate different functions.

Correct Answer: D

Rationale: The correct answer is D: eubiosis. Eubiosis refers to a state of balance and harmony among the species in the normal microflora. This term signifies a healthy and stable microbial community. Dysbiosis (A) is the opposite, indicating an imbalance or disruption in the microflora. Eukaryota (B) refers to organisms with cells containing a nucleus, not specifically related to the balance of microflora. Dispersion (C) refers to the spreading or distribution of microorganisms, not specifically related to their balance. In summary, eubiosis best describes the dynamic balance of species in the normal microflora, making it the correct choice.

Correct Answer: A

Rationale: Rationale: 1. Salmonella typhi causes typhoid fever, which can lead to intestinal infections. 2. Shigella flexneri causes dysentery, primarily affecting the colon. 3. Helicobacter pylori causes stomach ulcers, not intestine infections. Summary: A is correct as Salmonella typhi causes intestine infection. B and C are incorrect as they cause different gastrointestinal issues. D is incorrect as A is a valid choice.

Correct Answer: A

Rationale: The correct answer is A: Rifampicin. Rifampicin is known to cause red discoloration of bodily fluids, including tears and urine, due to its side effect of harmless color changes. Benzylpenicillins (B and C) and Biseptol-480 do not typically cause such discoloration. Rifampicin's mechanism of action involves binding to bacterial RNA polymerase, leading to inhibition of RNA synthesis, which is unrelated to the mechanism of the other drugs. Thus, based on the unique side effect profile of Rifampicin and its mechanism of action, it is the most likely drug causing red tears and urine in this scenario.

Correct Answer: D

Rationale: The correct answer is D: Imipenem. Imipenem is a carbapenem antibiotic effective against multiple-resistant microorganisms due to its broad spectrum and resistance to beta-lactamases. It is often used as a last resort for severe infections. Ampicillin (A) and Penicillin (B) are both beta-lactam antibiotics that are less effective against multiple-resistant microorganisms due to widespread resistance mechanisms. Augmentin (C) is a combination of amoxicillin and clavulanic acid, which may have limited efficacy against certain resistant strains but is not as effective as imipenem for treating infections caused by multiple-resistant microorganisms.

Correct Answer: A

Rationale: The correct answer is A: TRUE. B-lymphocyte antigen receptors are made by proteins called immunoglobulins. These proteins are essential for recognizing and binding to specific antigens. They play a crucial role in the immune response. Choice B is incorrect because B-lymphocyte antigen receptors are indeed made by proteins. Choice C is incorrect as well because in this case, the correct answer is that the receptors are made by proteins. Choice D is also incorrect as the receptors are made by proteins.

Correct Answer: D

Rationale: The correct answer is D because all three choices, Clostridium botulinum, Morbillivirus morbillorum, and Clostridium tetani, can cause infections of the CNS. Clostridium botulinum can lead to botulism, affecting the nervous system. Morbillivirus morbillorum can cause measles, which can lead to encephalitis. Clostridium tetani can cause tetanus, affecting the central nervous system. Therefore, all three choices can cause infections of the CNS. Choices A, B, and C are incorrect individually because each pathogen can cause CNS infections.