Which organism is the etiologic agent most commonly associated with septicemia and meningitis of newborns?

• A. Streptococcus agalactiae
• B. Streptococcus bovis group
• C. Streptococcus pneumoniae
• D. Streptococcus pyogenes

Answer: (A)

The main idea here is that neonatal septicemia and meningitis most often arise from maternal carriage of group B Streptococcus during birth. Group B Streptococcus (Streptococcus agalactiae) commonly colonizes the maternal genital tract and can be transmitted to the newborn during delivery, leading to early-onset sepsis and meningitis in the first days of life. Among the organisms listed, this one is the classic and most frequent cause of these neonatal infections because of its high rate of perinatal transmission and ability to invade the newborn’s bloodstream and meninges.

Helpful context: Group B Streptococcus is a gram-positive coccus in chains that shows beta-hemolysis on blood agar and is identified by the Lancefield group B carbohydrate; laboratory tests like the CAMP test and hippurate hydrolysis can aid confirmation. Prevention through maternal screening during late pregnancy and intrapartum antibiotic prophylaxis has substantially reduced the burden of neonatal GBS disease.

Streptococcus pneumoniae, while a common cause of meningitis in older infants and adults, is not the most frequent neonatal pathogen. Streptococcus pyogenes can cause severe neonatal infections but is far less common in this context. The Streptococcus bovis group is typically associated with gastrointestinal disease and endocarditis in adults rather than neonatal meningitis.