What organism likely causes meningitis in a neonate presenting with gram-negative straight rods and a yellow pigment on culture?

The presence of gram-negative straight rods along with the indication of yellow pigmentation on culture strongly points to Chryseobacterium meningosepticum as the likely causative organism of meningitis in a neonate. Chryseobacterium meningosepticum, formerly known as CDC group II, is known for its characteristic yellow-pigmented colonies when cultured on certain media. This organism is commonly associated with infections in neonates, particularly in premature infants or those with underlying conditions, making it a frequent cause of meningitis in this vulnerable population.

The combination of its morphological characteristics and its clinical associations in neonates helps to solidify its identity as the likely pathogen in this scenario. Other organisms may share certain traits but do not typically present with yellow pigmentation or have the same clinical relevance in neonatal meningitis.