GROUP B STREPTOCOCCUS


I. Group B Strep colonizes 15-40% of women; most women who are colonized at deliver can be identified by obtaining 3rd-trimester specimens for culture from lower vagina & rectum

II. Neonatal infection

  1. Attack rate = 1:100 in colonized moms, up to 1:25 with risk factors: prematurity, clinical GBS infection of a previous baby, prolonged ROM, maternal fever
  2. Early onset (<7d) consist of bacteremia, pneumonia, & meningitis
  1. 2/3 clinically evident in first 6h of life
  2. Mortality with early-onset neonatal infection = 15%
  3. Risk factors (other than maternal GBS colonization) include: prolonged ROM, intrapartum fever, < 37wks gestation, GBS bacteriuria during pregnancy, previous delivery of infant w/GBS disease
  1. HOWEVER< 25% of early-onset cases occur in infants of GBS carriers without risk factors!
  1. Can be prevented by administering prophylactic abx during labor
  1. Late-onset (>7d) usually results in meningitis
  1. 50% of these cases are postnatally acquired

III. Maternal infection (endometritis)

  1. Risk factors include heavy colonization, c/s, DM

IV. Management

  1. Antepartum abx for colonized moms not indicated b/c of low attack rate & high relapse rate
  2. In moms at high risk for preterm labor, however, may reduce risk by treating GBS colonization of urine
  3. Intrapartum ABX shown to be beneficial if PTL, PROM, ROM >18h, a previous child with symptomatic GBS infection, mult. gestations, or fever in labor. In the absence of these risk factors, benefits are unclear.
  4. One series out of Dallas compared cohorts of infants born under different management policies: 80,000 infants received PCN G IM at birth; 180,000 did not. No screening occurred. Sig. less early-onset GBS (without a secondary increase in late-onset GBS) in those treated with PCN (RR 0.25-0.5) (Obs. Gyn. 87:692, 1996-JW)
  5. CDC recommendations (MMWR 45:1, 1996)
  1. The following women will require intrapartum abx regardless of screen results so don't bother screening
  1. GBS bacteriuria (indicates high level of carriage)
  2. Women who gave birth in past to an infant w/GBS disease
  1. For all others, screen with distal vag-rectal cx at 35-37 weeks (screening late in pregnancy will help reduce false-negatives and false-positives)
  2. DON'T treat GBS carriage antenatally (except for GBS bacteriuria which increases risk of PTL)
  3. Offer intrapartum abx to:
  1. Women with h/o infant with GBS disease
  2. Women with GBS bacteriuria during present pregnancy
  3. Women with positive GBS screen
  4. Women whose GBS status is unknown at time of labor AND any of the following:
  1. Are at < 37 weeks' gestation
  2. ROM > 18h
  3. T > 100.4 (38.0)
  1. Meds: from admit till delivery
  1. PCN G 5mU IV then 2.5mU Q4h (preferred) OR
  2. Ampicillin 2g then 1g Q4h
  3. For PCN-allergic, clindamycin (900mg IV Q8h) or erythromycin (500mg IV Q6h)
    1. Note that GBS resistance to clindamycin and erythromycin has been reported as of 1999 (e.g. Obs. Gyn 92:258, 1998--AFP) so consider skin testing to verify reported PCN allergy in GBS-positive moms
  1. Management of baby
  1. Routine use of abx for baby is not recommended except for babies < 35 wks, in whom empiric abx and "full diagnostic evaluation" w/CBC, blood cx, & CXR and LP if clinically indicated, is also recommended
  2. If duration of intrapartum abx was > 4h, should just keep in hosp and observe 48h or more (no early d/c for these kids)
  3. If had intrapartum abx for < 4h, also recommend "limited evaluation" w/CBC and blood cx and observation for 48h or more
  4. In all, if clinically suspect sepsis, do full sepsis w/u.