Final answer:
Group B streptococcus (S. agalactiae) is the primary cause of neonatal meningitis and other serious infections in newborns. It is a gram-positive bacterium, distinct from Group A streptococcus, known for its capacity to colonize the human gastrointestinal and urogenital tracts and its arsenal of virulence factors that facilitate infection and evade the immune response.
Step-by-step explanation:
Streptococcus agalactiae, or Group B streptococcus (GBS), is a significant pathogen responsible for neonatal infections, including neonatal meningitis.
This pathogen is an encapsulated gram-positive bacterium found in the gastrointestinal and urogenital microbiota of about 10-30% of the human population. It can cause meningitis not only in neonates but in individuals of all ages.
Comparison to Group A Streptococcus:
Unlike Group A streptococcus (S. pyogenes), which is associated with diseases such as streptococcal pharyngitis (strep throat), rheumatic fever, and scarlet fever, Group B strep is most recognized for its impact on newborns. GBS can be particularly dangerous in this group due to the development of diseases such as meningitis, pneumonia, and sepsis.
Group A strep has more than 80 strains identified by their surface M proteins, which contribute to their virulence and diversity in causing infections.
Virulence Factors of S. agalactiae:
GBS is equipped with numerous virulence factors that contribute to its pathogenicity. It possesses FbsA that facilitates adhesion to host cells, PI-1 pili that enhances invasion of endothelial cells, a polysaccharide capsule that hinders phagocytosis, and CAMP factor, which disrupts host cell membranes and can bind to antibodies.
These factors underscore the importance of identifying and managing S. agalactiae infections in pregnant women and newborns to prevent serious illness and potential mortality.