What condition is caused by the infection of cerebrospinal fluid by Streptococcus pneumoniae and Neisseria meningitides?

The condition caused by the infection of cerebrospinal fluid specifically by Streptococcus pneumoniae and Neisseria meningitidis is meningitis. Meningitis refers to the inflammation of the protective membranes covering the brain and spinal cord, known as the meninges. This inflammation is typically a result of an infection, which can be caused by bacteria, viruses, fungi, or parasites.

Streptococcus pneumoniae and Neisseria meningitidis are both bacterial pathogens that commonly lead to bacterial meningitis. When either of these bacteria invade the cerebrospinal fluid, they can cause severe symptoms including fever, headache, neck stiffness, and altered mental status. This condition often requires prompt medical treatment, typically with antibiotics, to prevent serious complications or death.

The other options do not encompass the specific conditions caused by these bacteria in relation to cerebrospinal fluid. Encephalitis refers to the inflammation of the brain itself, while myelitis is inflammation of the spinal cord. An aneurysm, on the other hand, involves a bulge in a blood vessel and is not related to the infection of cerebrospinal fluid. Thus, meningitis is the correct response in this context, highlighting the serious nature of infections involving the central nervous system.