Final answer:
The most common bacteria associated with bacteremia and pneumonia in IV drug users include Staphylococcus aureus (particularly MRSA) and Streptococcus pneumoniae.
Step-by-step explanation:
Most common Bug in IV drug user bacteremia / pneumonia
Intravenous (IV) drug users are at an increased risk of developing bacteremia and pneumonia due to their higher susceptibility to infections. The most common bacteria associated with these infections in IV drug users include Staphylococcus aureus, particularly methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus pneumoniae.
These bacteria can enter the bloodstream through contaminated needles or unclean injection sites and cause bacteremia. From there, they can spread to the lungs and cause pneumonia. IV drug users are also at risk of developing other infections, such as endocarditis, which is an infection of the heart valves.