Final answer:
The most common organism involved in carbuncle infections like the one Steve experienced is Staphylococcus aureus, which may be resistant to many antibiotics and can lead to MRSA.
Step-by-step explanation:
The most common organism involved in cases like Steve's, where a carbuncle on the neck was treated with an incision and drainage, followed by antibiotics, is Staphylococcus aureus. This bacterium is known for causing skin infections, including furuncles and carbuncles.
Staphylococcus aureus can be particularly problematic because it may be resistant to many common antibiotics, leading to the increasing occurrence of methicillin-resistant Staphylococcus aureus (MRSA) infections. Laboratory tests, such as Gram staining and culture, as well as additional tests such as passive agglutination, are used to confirm the presence of these organisms.