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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Group B Streptococcal Disease in the Perinatal Period
Sponsored by The Indian Health Service Clinical Support Center
4. Summary of the 2002 CDC Revised Recommendations
- All pregnant women should be screened at 35-37 weeks
gestation for vaginal and rectal GBS colonization. At the time of labor or rupture
of membranes, intrapartum chemoprophylaxis should be given to all pregnant women
identified as GBS carriers.
- Colonization during a previous pregnancy is not an
indication for intrapartum prophylaxis in the current pregnancy. Having had a
previous infant affected by invasive GBS disease is an indication for intrapartum
prophylaxis and culture-based screening is not necessary for these women.
- Women with GBS bacteriuria during the present pregnancy
should be treated with oral antibiotics at the time of diagnosis, do not need
further screening at 35-37 weeks, and should also receive intrapartum prophylaxis.
- For women who have not received prenatal care, or in
whom the result of the GBS culture is not known at the onset of labor, intrapartum
chemoprophylaxis should be administered when these risk factors are present:
1) gestation <37 weeks
2) membranes ruptured for >18 hours
3) temperature > 38 degrees C or 100.4 degrees F.
- Women with onset of membrane rupture or labor at <37
weeks gestation should have vaginal and rectal culture collected for GBS and
should be begun on antibiotic prophylaxis. If there is no growth of GBS at 48
hours, antibiotics may be stopped. If the patient is found to be GBS positive,
antibiotics may be stopped at 48 hours if tocolysis is achieved, but they should
be restarted at the time of delivery.
- Collection of specimens for GBS culture should include
both vaginal (lower third) and rectal (insert through sphincter) samples. Either
the patient or the provider may collect the samples.
A speculum is not recommended as the specimen is not to be collected from the cervix. Two swabs should be used and both should be put into the same tube of transport medium. Specimens should initially be inoculated into selective medium (Lim or Todd-Hewitt), not blood agar.
- Providers should inform women of their GBS screening
test result and the recommendations. Antimicrobial agents should not be used
before the intrapartum period as treatment prior to labor is not effective in
eliminating GBS carriage. Women with GBS bacteriuria are an exception however
and they should be treated with oral antibiotics at the time of diagnosis, do
not need further screening at 35-37 weeks, and should receive intrapartum chemoprophylaxis.
- GBS-colonized women who have a planned cesarean delivery
prior to the onset of labor or membrane rupture do not need intrapartum chemoprophylaxis.
- Women with a negative antenatal GBS screening culture
in the current pregnancy, regardless of intrapartum risk factors, do not need
intrapartum prophylaxis.
- For intrapartum
chemoprophylaxis for women without penicillin allergy, the following regimen
is recommended: penicillin G 5 mullion units IV load, then 2.5 million units
IV q4h until delivery. Because of concerns about the emergence of bacterial resistance,
penicillin is the preferred drug, but as an alternative, ampicillin 2g IV initially,
followed by 1g IV q4h until delivery is also acceptable.
- For intrapartum
chemoprophylaxis for penicillin-allergic women, factors relating to bacterial
resistance and patient history must be taken into account. If a patient does
not have a history of an immediate hypersensitivity reaction (anaphylaxis, angioedema,
or urticaria) to penicillin, the drug of choice is cefazolin 2g IV loading dose,
followed by 1g IV q8h until delivery. Cephalosporins may have up to a 10% crossover
risk of a reaction in patients with penicillin allergy, but the vast majority
of these are mild reactions (transient rash).
As many as 15 to 25% of GBS isolates are resistant to both erythromycin and clindamycin, therefore women who are at high risk for anaphylaxis should have sensitivity requested on their GBS culture at the time of screening.
If the patient’s GBS is sensitive to erythromycin or clindamycin, the appropriate doses are: erythromycin 500 mg IV q6h until delivery, or clindamycin 900 mg IV q8h until delivery.
If susceptibility testing is not available, or results are unknown, or isolates are resistant, then the following regimen should be used: vancomycin 1g IV q12h until delivery.
- If a patient has overt clinical chorioamnionitis, a
polymicrobial infection, the most appropriate regimen is broad spectrum, and
should include ampicillin 2g IV q4h, plus gentamicin 2.5 mg/kg loading dose,
followed by 2.0 mg/kg IV q8h until delivery.
- Management of infants born to mothers who received
intrapartum chemoprophylaxis for GBS infection also involves cost and convenience
issues and institutional preferences may modify the approach suggested here.
If the infant has clinical signs of sepsis, then a full diagnostic evaluation
with CBC, blood culture, and lumbar puncture is indicated, along with institution
of appropriate treatment with parenteral ampicillin and gentamicin. If the mother
had frank chorioamnionitis, her newborn should also have a full diagnostic evaluation
and be begun on empiric therapy with ampicillin and gentamicin pending culture
results.
On the other end of the spectrum, a healthy-appearing term infant whose mother received >4 hours of intrapartum antibiotic prophylaxis with penicillin, ampicillin, or cefazolin before delivery may be discharged home as early as 24 hours after delivery. This assumes the home caregiver has the ability to observe the infant and is able to bring the infant for evaluation if concern exists.
If that is not the home situation, and it may well not be for our rural patients, then 48 hours of observation in hospital is probably more appropriate. Data on best management after the use of other antibiotics is not available.
If the infant is <35 weeks gestation, or did not receive standard intrapartum antibiotic prophylaxis for at least 4 hours before delivery, but appears clinically well, then a limited evaluation with a blood culture, and observation for at least 48 hours would be a prudent management strategy. Signs of suspected sepsis should of course prompt full diagnostic evaluation and empiric antibiotics until cultures return.
- Future prevention strategies will hopefully involve
a rapid bedside test to detect the presence of GBS antigen in carrier women who
have not been screened, but the currently available rapid tests are insufficiently
sensitive for this purpose and at present cannot replace cultures.
Immunization of women during or before pregnancy could provide protection to their infants through the transplacental passage of IgG antibodies, and such vaccines produced to GBS capsular polysaccharide antigens are currently in clinical trials. Intrapartum chemoprophylaxis is not a permanent or comprehensive strategy for prevention of GBS disease, but it is the current recommended strategy until a safe and effective vaccine can be produced.
