Answer:
The correct answer is a. Group B Streptococcus.
Group B Streptococcus (GBS) is the most common cause of serious neonatal infections, including sepsis, pneumonia, and meningitis. GBS can be vertically transmitted from a colonized mother to her baby during pregnancy, labor, or delivery.
The other options are not associated with vertical transmission leading to these serious neonatal infections:
- Mobiluncus curtisii is an anaerobic bacterium associated with bacterial vaginosis, but not with vertical transmission of infections.
- Lactobacillus species are normal vaginal flora and not associated with vertical transmission of infections.
- Gardnerella vaginalis is also associated with bacterial vaginosis, but not with vertical transmission of infections.