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CDC updates GBS prevention guidelines.

The incidence of group B streptococcal disease in infants has declined sharply since guidelines for prevention were implemented nearly 15 years ago, but GBS nonetheless remains the leading infectious cause of morbidity and mortality among infants in the United States, according to the Centers for Disease Control and Prevention, which recently updated the guidelines to further promote prevention efforts.

Since the guidelines were first published by the CDC in 1996 - then updated and republished in 2002 - the number of cases per 1,000 live births has declined from 1.7 to 0.23-0.37. Universal screening at 35-37 weeks' gestation and the use of intrapartum antibiotic prophylaxis as recommended in the original and updated guidelines is credited for this improvement, but the rates of maternal colonization, and therefore the risk of early-onset disease in the absence of intrapartum antibiotic prophylaxis, has remained unchanged since the 1970s.

"The continued burden of disease and newly available data relevant to early-onset GBS disease prevention from the fields of epidemiology, obstetrics, neonatology, microbiology, molecular biology, and pharmacology prompted revision of the guidelines for early-onset GBS disease prevention," according to the CDC's report introducing the most recently revised guidelines (MMWR 2010;59[RR-10]:1-32).

A technical working group identified a subset of topics for review, then revised the guidelines based on available evidence and expert opinion. Changes were made regarding both secondary prevention in newborns and maternal prophylaxis.

In large part, the revised guidelines are reaffirmation of the earlier guidelines, according to Dr. Sarah J. Kilpatrick, chair of the department of obstetrics and gynecology at Cedars Sinai Medical Center, Los Angeles, and an American College of Obstetricians and Gynecologists representative on the technical working group charged with updating the guidelines.

"The major point is that the guidelines still recommend screening all pregnant women between 35 and 37 weeks. That's unchanged, and that's an important message," Dr. Kilpatrick said in an interview.

Other changes in regard to the mother are mostly designed to clarify and simplify the recommendations and to emphasize how important it is that obstetrics providers follow the guidelines, she said. The updated guidelines do the following:

* Provide two new diagrams to demonstrate the management of GBS prophylaxis in preterm labor and in preterm premature rupture of the membranes (PPROM). These provide clarifications and highlight the important point that GBS prophylaxis in those patients is indicated if patients are very likely to deliver.

* Call for a change in the dose of penicillin G for chemoprophylaxis. Penicillin remains the recommended drug for treatment, but the dose is changed slightly - to 5 million units intravenously, followed by 2.5-3.0 million units intravenously every 4 hours (the range is recommended to achieve adequate drug levels in the fetal circulation and amniotic fluid while avoiding neurotoxicity). The choice of dose also should be guided by which formulations are readily available in order to reduce the need for specially prepared doses.

* Update the prophylaxis regimens for women with penicillin allergy and state that erythromycin is no longer an acceptable alternative for prophylaxis in women with penicillin allergy and a high risk for anaphylaxis.

* Clarify the definition of high-risk anaphylaxis as a history of anaphylaxis, angioedema, respiratory distress, or urticaria following administration of penicillin or a cephalosporin.

* Recommend that cefazolin be used for prophylaxis in those who have a nonsevere penicillin allergy.

The guidelines also clarify which patients do not need prophylaxis, Dr. Kilpatrick said. A woman with appropriate cultures showing that she is GBS negative, for example, does not need prophylaxis -even if she presents with PPROM. This was included in the earlier guidelines, but it is clarified in the new guidelines.

As for secondary prevention in neonates, a management algorithm for secondary GBS prevention, which is designed to detect potential cases as early as possible, remained mostly the same, except it was streamlined and now applies to all newborns, according to Dr. Carol Baker, professor of pediatrics, molecular virology and microbiology at the Baylor College of Medicine, Houston, and also a member of the technical working group.

Although the changes in the guidelines are generally small when it comes to secondary prevention in infants, they are important and, taken together, the changes for both mothers and babies are expected to provide some incremental improvements in outcome, Dr. Baker said.

"GBS will never go away completely in newborns, but some of the cases are cases where the guidelines are not followed," Dr. Kilpatrick added, noting that she, too, is hopeful that the clarifications in the new guidelines will make them easier to follow, and that as a result, there will be very few patients who do not get appropriate treatment.

The guidelines have been endorsed by ACOG, the American Academy of Pediatrics, the American College of Nurse-Midwives, the American Academy of Family Physicians, and the American Society for Microbiology All have had a hand in developing the guidelines, and thus have a stake in the outcomes, Dr. Baker said.

"I'm very optimistic that there will be high compliance both on the baby side and the mother's side. It's a matter of education - hopefully the news will get out," Dr. Baker said.

Indeed, the guidelines call for local and state public health agencies, in conjunction with hospitals, to establish surveillance for early-onset GBS, and to "take other steps to promote perinatal GBS disease prevention and education to reduce the incidence of early-onset GBS disease in their states."

Also, research aimed at better understanding the racial and ethnic differences that still persist in GBS disease incidence is needed, according to the CDC report. Research is needed on strategies for preventing early-onset disease among preterm infants, effectiveness of the recommended intrapartum antibiotic prophylaxis agents for penicillin-allergic women at high risk for anaphylaxis, and factors contributing to the higher than anticipated proportion of early-onset GBS disease cases occurring among infants born to women with negative prenatal GBS screens.
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Author:Worcester, Sharon
Publication:OB GYN News
Date:Jan 1, 2011
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