Definition of Streptococcus, group B

Streptococcus, group B: A major cause of infections, including infections involving the pregnant woman and her newborn infant. Strep B can infect the mother's uterus, placenta, and urinary tract; in fact, they are present in the vagina of 10 to 25 percent of all pregnant women. Group B strep can be transferred between heterosexual couples by oral sex.

Infections in the infant can be localized, or may involve the entire body. In babies, strep infections are divided into early-onset and late-onset disease. Early-onset disease presents within the first six days of life with breathing difficulty, shock, pneumonia, and occasionally infection of the spinal fluid and brain (meningitis). Late-onset disease presents between the seventh day and the third month of age with a bloodstream infection (bacteremia) or meningitis. The bacteria can also infect an area of bone; a joint, like the knee or hip; or the skin.

Group B strep infection in the newborn is a serious and potentially life-threatening event, particularly because fever and warning signs are often minimal or absent, and because the newborn's immune system is not mature. Early signs of infection can be as subtle as poor feeding, lethargy, or poor temperature control. Women with vaginal group B strep can transmit it to their infant before birth, after the membranes are ruptured, or during the delivery. These babies have a .5 to 1 percent chance of contracting the early-onset type of infection. The risk rises with premature infants; infants born more than 18 hours after the amniotic membranes have ruptured; and infants whose mothers had fever, evidence of infection of the uterus lining, or infection of the urinary tract during labor and delivery. With many infants discharged less than 24 hours after birth today, there is growing pressure to culture all women during pregnancy for group B step.

Antibiotic treatment can be considered for culture-positive women before delivery. A positive culture permits the infant's doctor to be especially alert to early signs of problems. Group B strep infection of the newborn is treated aggressively with antibiotics, usually in a neonatal intensive care unit, but the disease still carries a significant mortality rate. Prevention and early detection are critically important.