Hepatitis B infection may present with:

Correct Answer: D

Rationale: The correct answer is D: All of the above. Hepatitis B infection can present with jaundice due to liver inflammation, elevated serum aminotransferase levels due to liver damage, and sometimes no symptoms in the acute phase. This comprehensive presentation covers the spectrum of possible clinical manifestations of hepatitis B infection. Choices A and B are correct as they are common manifestations of hepatitis B infection. Choice C is incorrect as hepatitis B infection can indeed present with symptoms, making option D the most appropriate choice.

Correct Answer: A

Rationale: The correct answer is A, proportion 4:1. Gram (+) bacteria have a higher ratio of MG-ribonucleate to Mg. deoxyribonucleate because ribosomal RNA is more abundant in actively growing bacterial cells. This higher proportion of MG-ribonucleate to Mg. deoxyribonucleate is essential for protein synthesis and growth. The other choices are incorrect because they do not reflect the higher ratio of ribosomal RNA to DNA in Gram (+) bacteria, which is crucial for their metabolic activities and cellular functions.

Correct Answer: A

Rationale: The presence of flagella in a bacterial cell represents the H-antigen. Flagella are protein structures on the cell surface that play a role in bacterial motility. The H-antigen refers to the flagellar antigen, which is involved in immune responses and bacterial identification. Option A is correct because flagella are specifically associated with the H-antigen. Summarily, choices B and C are incorrect because the O-antigen and K-antigen are associated with lipopolysaccharide and capsule antigens, respectively, not flagella. Option D is incorrect as well because the correct association is with the H-antigen.

Correct Answer: B

Rationale: The term bacilli refers to rod-shaped bacteria, typically found in the Gram-positive group. Spore-forming bacteria, such as Bacillus and Clostridium, are characterized by their rod shape. Choice A is incorrect as the color in Gram staining does not define bacilli. Choice C is incorrect as peptidoglycan content does not determine the classification of bacilli. Choice D is incorrect as bacilli do have a specific characteristic. Therefore, the correct answer is B due to the shape and characteristic of spore-forming bacteria.

Correct Answer: C

Rationale: Step 1: S. aureus is known to produce hemolysins, leucocidins, and enterotoxin. Step 2: S. aureus colonies usually exhibit golden-yellow pigmentation with beta-hemolytic zones. Step 3: S. aureus has developed resistance to penicillin due to the production of beta-lactamase. Step 4: Therefore, statement C is not true as S. aureus is not always sensitive to penicillin. Summary: Choices A and B are correct statements about S. aureus, while choice C is incorrect due to the increasing penicillin resistance seen in S. aureus.