A 1-day-old newborn is evaluated for possible sepsis. Blood cultures grow gram-positive cocci in pairs and chains that agglutinate with group B antiserum. The most likely epidemiologic risk factor for this infection involves bacterial colonization of which of the following?
(A) Mother’s vagina
(B) Newborn’s gastrointestinal tract
(C) Newborn’s nasopharynx
(E) Umbilical cord remnant
Correct answer : (A) Mother’s vagina
Explanation: This is a case of early onset sepsis in a newborn. The organism involved is Group B streptococci (gram-positive cocci in pairs and chains that agglutinate with group B antiserum). The source of infection is probably the mother’s vagina.