Which organism is a gram-positive aerobic cocci that causes rheumatic fever?

Streptococcus pyogenes is the organism responsible for rheumatic fever, making it the correct answer. This bacterium is a gram-positive aerobic cocci that is part of the group A streptococci. It is known for causing various infections, including strep throat, which can lead to complications such as rheumatic fever. This condition arises as a post-streptococcal complication, where the immune response to the infection mistakenly attacks the body's own tissues, particularly the heart, joints, skin, and central nervous system.

The other organisms listed do not cause rheumatic fever. Staphylococcus aureus, while also a gram-positive cocci, is typically associated with different infectious conditions, including skin infections and sepsis. Escherichia coli is a gram-negative bacillus predominantly associated with urinary tract infections and gastrointestinal issues, and Pseudomonas aeruginosa is a gram-negative bacillus known for its role in opportunistic infections, particularly in immunocompromised patients. Thus, the distinctive link between Streptococcus pyogenes and rheumatic fever highlights its role in this specific disease process.