Medical Definition of Infection, group B strep

Reviewed on 3/29/2021

Infection, group B strep: Group B strep are a major cause of infections involving the pregnant woman and her newborn infant, causing maternal infections of the uterus, placenta, and urinary tract and infections in the infant that can be localized or involving the infant's entire body. (Group B strep are not to be confused with group A strep, the bacterial cause of strep throats).

Group B strep infections in babies fall into two categories:

  1. Early-onset disease, presenting within the first 24 hours of life (or up 6 days of life) with breathing difficulty, shock, pneumonia, and occasionally spinal fluid/brain infection ("meningitis");
  2. Late-onset disease, presenting at 3 to 4 weeks of age (range, 7 days to 3 months) with a blood-stream 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 (or any bacterial) 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 infection-fighting immune system is not mature. The early signs of newborn infection can be as subtle as poor feeding, lethargy, or poor temperature control.

Group B strep infections in women occur because these bacteria commonly live in the intestinal and genital tracts. They are present in the vagina of 10-25% of pregnant women.

Transmission from mother to baby: Women with vaginal group B strep can transmit it to their infant before birth, or after the membranes are ruptured, or during the delivery. These babies have a 1/2-1% chance of contracting the early-onset type of infection. The risk of infection rises with premature infants, infants born after the amniotic membranes have ruptured for more than 18 hours, and infants whose mothers had fever or evidence of infection of the uterus lining and or urinary tract during labor and delivery.

With infants being discharged home today in less than 24 hours, there is growing pressure to culture all women during pregnancy to determine who may be carrying group B step (without having symptoms themselves). Antibiotic treatment can be considered for the culture-positive women BEFORE DELIVERY. A positive culture permits the infant's doctor to be especially alert to early signs of problems and watch the infant for an extra day or two.

Group B strep infection of the newborn, once diagnosed, is treated aggressively with antibiotics and care of the infant in a Neonatal ICU, but the disease still carries a significant mortality rate. Prevention and early detection are critically important.



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