Microbiology An IV drug user is diagnosed to have infective endocarditis involving the tricuspid valve. Which of the following is the most likely causative agent? A Staphylococcus aureus B Streptococcus gallolyticus C Pseudomonas aeruginosa D Streptococcus pyogens 💡 Explanation An IV drug user is diagnosed to have infective endocarditis involving the tricuspid valve. Which of the following is the most likely causative agent? ✓ Correct Answer: A. Staphylococcus aureus