Gram-Positive vs Gram-Negative Cell Wall

A 42-year-old man with diabetes presents to the emergency department with fever (39.8°C), hypotension (BP 88/52 mmHg), and altered mental status. Blood cultures grow Gram-negative rods. The structure marked **B** in the diagram contains the endotoxin responsible for his clinical deterioration. Which of the following best explains why initiating antibiotic therapy in this patient may paradoxically worsen his septic shock in the first few hours?

A 45-year-old Indian male with prosthetic heart valve develops fever and new cardiac murmur. Blood cultures grow Enterococcus faecalis. The structure marked **A** in the diagram (thick peptidoglycan layer of Gram-positive bacteria) is the target site for vancomycin therapy. Which of the following best explains why vancomycin is effective against this organism but would be ineffective if the same pathogen were Gram-negative?