This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
A 30 years old patient with CSF leak is presenting with neck rigidity, fever and seizures. What could be the probable infective agent - 
Select and explain. 
A. Streptococcus pneumoniae, B. N. meningitidis, C. Listeria monocytogenes, D. Ecoli
A: Streptococcus pneumoniae
Answer: A: Streptococcus pneumoniae 
Explanation: Ans. is 'a' i.e., Streptococcus pneumoniae * Streptococcus pneumoniae is the most common cause of meningitis in adults older than 20 years of age.* A number of predisposing conditions increase the risk of pneumococcal meningitis, the most common of which is pneumonia.* Additional risk factors include alcoholism, acute and chronic otitis media, diabetes, splenectomy, hypogamaglobulinemia and head trauma with basilar skull fracture and CSF leak.