Final answer:
The most common pathogens in brain abscess include Streptococcus viridans and Staphylococcus aureus, with MRI with contrast being the preferred imaging technique due to its sensitivity in detecting brain abscesses.
Step-by-step explanation:
The most common pathogens in brain abscess are Streptococcus viridans, Staphylococcus aureus, Fusobacterium nucleatum, and Streptococcus pneumoniae. The optimal imaging technique for a brain abscess is MRI with contrast, as it provides better differentiation of the abscess from surrounding brain tissue and can better delineate the extent of the infection. Although CT scan with contrast can also be used and is more readily available, MRI with contrast is more sensitive and specific for detecting a brain abscess. We know that, apart from the above mentioned, organisms like Haemophilus influenzae, Neisseria meningitidis, and the ones that cause bacterial meningitis, such as Neisseria meningitidis and Listeria monocytogenes, can invade the blood-brain barrier and potentially lead to abscess formation.