Most common organism causing meningitis in a 1 year old child is:
Streptococcus pneumoniae
H. influenza
Listeria
Neisseria meningitidis
The common organisms causing acute bacterial meningitis in the neonatal period are E.coli, Streptococcus pneumonia, Salmonella species, Pseudomonas aeruoginosa, Streptococcus fecalis and Staphylococcus aureus. Ref: Ghai Essential Pediatris - 6th Edition, Page 517; Nelson 17th Edition, Page 2308.