What is the most common cause of congenital pneumonia in a 2-day-old infant?

The most common cause of congenital pneumonia in a 2-day-old infant is Group B Streptococcus. This bacterium is frequently found in the gastrointestinal flora of pregnant women and can be transmitted to the infant during delivery, particularly if the mother is colonized with the bacteria. In neonates, especially those less than a week old, Group B Streptococcus is a leading cause of early-onset sepsis and pneumonia, making it a significant concern in newborn care.

Staphylococcus epidermidis, while a possible pathogen in various infections, including catheter-related and skin infections, is not typically linked to congenital pneumonia as its primary cause. E. coli can also cause neonatal infections and sepsis, but it is more commonly associated with urinal tract infections and other hospital-acquired infections in neonates rather than with congenital pneumonia at such an early age. Ureaplasma urealyticum is associated with respiratory complications and other infections, but it is much less common as a direct causative agent of pneumonia in newborns compared to Group B Streptococcus.