Disinfection with chemicals acting on cell surface:

Correct Answer: B

Rationale: The correct answer is B: Phenols. Phenols act on the cell surface by disrupting cell membranes and denaturing proteins, leading to cell death. Soaps (A) work by lifting dirt and microbes off surfaces, not directly acting on cell surfaces. Amines (C) are typically used as disinfectants targeting specific enzymes in microbes, not cell surfaces. Polymyxin (D) is an antibiotic that works by disrupting cell membranes internally, not on the cell surface.

Correct Answer: B

Rationale: The correct answer is B: Ascomycota. Penicillin is produced by the mold Penicillium, which belongs to the phylum Ascomycota. Ascomycota is known for its sac-like structures called asci that contain ascospores. Penicillium produces penicillin as a defense mechanism against bacteria. Basidiomycota (A) are known for producing mushrooms, Zygomycota (C) includes bread molds like Rhizopus, and Deuteromycota (D) is a classification for fungi with no known sexual reproductive stage.

Correct Answer: D

Rationale: The correct answer is D: amensalism. Penicillin mold produces a substance that inhibits the growth of bacteria, but it does not benefit nor harm the bacteria directly. This relationship is characterized by one organism (the mold) negatively affecting another (the bacteria) without any benefit or harm to itself. In parasitism (A), one organism benefits at the expense of another. In mutualism (B), both organisms benefit from the relationship. In commensalism (C), one organism benefits while the other is unaffected. Therefore, the mold producing penicillin fits the definition of amensalism.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This is because the bacterium is Gram-positive cocci in pairs, catalase-negative, and alpha-hemolytic, which are characteristic features of S. pneumoniae. The other choices can be ruled out based on specific characteristics: B) Staphylococcus aureus is catalase-positive, C) Enterococcus faecalis is gamma-hemolytic, and D) Neisseria gonorrhoeae is a Gram-negative diplococcus. Therefore, based on the given information, S. pneumoniae is the most likely causative agent of the sepsis.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus aureus. Staphylococcus aureus is a Gram-positive cocci bacterium that forms clusters and commonly causes pneumonia with a productive cough and fever. It is frequently found in sputum smears in such cases. Streptococcus pneumoniae (B) is another common cause of pneumonia but typically appears in pairs or chains, not clusters. Neisseria meningitidis (C) is a Gram-negative diplococcus that causes meningitis, not pneumonia. Klebsiella pneumoniae (D) is a Gram-negative bacterium that can cause pneumonia but appears as Gram-negative rods, not Gram-positive cocci in clusters.

Correct Answer: B

Rationale: The correct answer is B: Jenner. Edward Jenner is credited with performing the first successful vaccination against smallpox in 1796. He used cowpox virus to inoculate individuals, leading to immunity against smallpox. Jenner's experiment laid the foundation for modern vaccination. Pasteur (A) is known for developing the germ theory of disease. Semmelweis (C) advocated for handwashing to prevent infections. Koch (D) identified the causative agents of several diseases but did not develop the smallpox vaccine.

Correct Answer: C

Rationale: Step 1: Togaviridae is a family of viruses known to have non-segmented (+)ssRNA as their genetic material. Step 2: The positive sense RNA means that the viral RNA can be directly translated into proteins by host machinery. Step 3: This RNA genome acts as mRNA, allowing for immediate translation of viral proteins. Step 4: Therefore, choice C is correct as it accurately describes the genetic nature of Togaviridae. Summary: - Choice A is incorrect because Togaviridae viruses do not have helical symmetry. - Choice B is incorrect because Togaviridae viruses do not have non-segmented (-)dsRNA. - Choice D is incorrect because Togaviridae viruses are enveloped viruses.

Correct Answer: C

Rationale: The correct answer is C: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis as it specifically infects the lungs and can spread to other parts of the body. Mycobacterium leprae (A) causes leprosy, Streptococcus pneumoniae (B) causes pneumonia, and Clostridium botulinum (D) causes botulism, making them incorrect choices for tuberculosis. Mycobacterium tuberculosis has unique characteristics and mechanisms that enable it to cause tuberculosis, such as its ability to evade the immune system and form granulomas in the lungs.

Correct Answer: D

Rationale: The correct answer is D: All are correct. Patients planned for treatment with monoclonal antibodies should be tested for HBV, HCV, and M. tuberculosis due to the risk of reactivation of these infections during treatment. HBV and HCV reactivation can lead to severe liver damage, while M. tuberculosis reactivation can cause serious respiratory complications. Testing for all three infections helps in identifying and managing any pre-existing infections to ensure patient safety during monoclonal antibody treatment. Choices A, B, and C are incorrect because each of these infections presents specific risks that need to be assessed before initiating monoclonal antibody therapy.